Planet HamBrew

January 20, 2010

John Harper, AE5X

These guys have cojones…

logo-yiFrom April 2-12, a multi-national team will be airing a major DXpedition from Iraq. Full details are posted on their website here. Fortunately, they’ll be operating from Kurdistan, a relatively safe part of the country.

Elecraft’s K3s are sure making it to some far-flung places around the world and will be doing so for these guys too.

And judging from the rest of their equipment list, they should be putting loud signals on numerous bands. Hopefully band conditions will cooperate and a lot of DXers will get a “new one” out of this.

Due to a lot of servicemen from various countries over the years, Iraq is not as rare as it once was. Thanks to LZ1ZF/YI9ZF, I have Iraq worked & confirmed on 15, 30 and 40 meters. Sure would like to get YI on 80 meters…..

Surprisingly, it’s not even in the top 100 Most Needed according to one source. I’m not sure if I believe that as several of the countries listed have seen recent & large DXpeditions that should have lowered their ranking on this list, such as Kingman Reef.

Speaking of Most Needed lists, here’s a survey for 2010 if you’re interested.

.

.

by John Harper AE5X at January 20, 2010 18:29

Joachim, DL1GSJ

Rock-Mite mod

The trick with the Rock-Mite is the PIC (programmable interface controller) which provides keying, RIT and other functions. It is a 12C508 which is pin-compatible to the 12F629 and in a way also to the PICAXE-08M. The main modification would be to write a new firmware for the controller, hence the MEPT/RX would have an onboard beacon keyer.

Check out the schematics:


The Rock-Mite uses a simple oscillator (Q4,Y2) which is pulled (D6) for RIT. Some options here:
  1. replace the varicap diode by a rectifier or LED and FSK the oscillator with Q1
  2. leave the RIT alone (allowing for beat offset) and add keying voltage from GP2 (pin 5, PWM!) via some low-pass filter and resistors
  3. reroute Q2 to GP0 and add extra crystal pulling by using GP2's pseudo DAC (PWM)
I will probably go for option 3.
Option 3 opens this: Use ADC4 (pin 3) for a QRG control via a potentiometer.

The receiver will remain nearly untouched, it already employs a crystal filter and all things needed for grabbing. C1 and C2 however should be replaced by trimmers, so that the filter can be tuned.

With all that said, looking what still is left of the controller, GP0, GP1 and GP3.



When using a PICAXE, GP0 is "out" only. This could be used for RIT control, when using Q2, as indicated above.
GP1 is a digital input and GP3 is an analog/digital input/output. I figure that GP1 could seve as a receive/transmit toggle. Now we are left with one single analog/digital IN/OUT port. What about Johan's idea of including telemetry?

There you have it, the by far best kit to convert to QRSS. BTW: Programming the PICAXE chips is really simple. With a little bit more effort, the 12F629 offers more to play with, in particular more memory.
PICAXE: http://www.rev-ed.co.uk/picaxe/


by PA1GSJ (noreply@blogger.com) at January 20, 2010 09:16

Ramsey QRP80C oscillator test


As promised, the results of the stability test of the Ramsey QRP80C oscillator. The oscillator is built using a new 3.579MHz crystal, no inductor and 1N4007 diodes in place of the varicap diodes. The following spectra show the carrier of the oscillator as received by the SR80lite. I did tests on upper and lower band edge, keying (by powering the oscillator) and some frequency sweeping.
Next to the stability of the oscillator, this test also shows how quiet the color burst frequency actually is. As soon as the TV qrm stops, it is clear that the signal carries some 50Hz hum, probably due to the power supply (rather old R&S regulated lab PSU).
Here is what the test looked like:

Power up, handling of the PCB, touching the xtal and some inital drift


Change from lowest to highest qrg


How stable is it when set anywhere else?


Keying test, since I shorted the keying, this was done by pulling the power cable from the PSU.


Some faster QRG changes and a final slow sweep, note the 50Hz when the next door TV gave me a break...


Some more stability in the midrange, note how clean the frequency range is...


HA! Finally something else (psk31) than just my carrier (draaggolf) and the TV set...



Some more lonely carrier...


And some final wiper play with the pot.



by PA1GSJ (noreply@blogger.com) at January 20, 2010 09:13

Hamsexy dot com

Ottawa radio pirate update…

Details are sketchy, but it looks like Jayhaed Saade was back on the air for a brief time today. Listeners to his internet stream reported on Digital Home that he was back on the air with a 30 watt transmitter and apparently tired to kill himself, forcing several listeners to call 911 and causing an [...]

by admin at January 20, 2010 01:46

John Harper, AE5X

New one on 80m

I really don’t know how it was possible – lots of stations calling him and he wasn’t that strong here. I was using 100 watts and a dipole and got 5N50K (Nigeria) on the 4th call on 3505 kHz.

I’d sure like to know what his rig/antenna was to have heard my puny call!

He wasn’t new overall but was my 133rd country on 80 (and my 48th on 80 since moving to 5-Land last February).

.

.

by John Harper AE5X at January 20, 2010 01:40

January 19, 2010

Joachim, DL1GSJ

7493 ripple counter keying

Well, tiny idea about the keying I was writing about in an ealier posting.
There are two pins (2&3) either one enabling counting when grounded. This lead to the idea of having one wired up a Morse key (or keyer) with all the

by PA1GSJ (noreply@blogger.com) at January 19, 2010 16:34

January 18, 2010

Joachim, DL1GSJ

QRP80C update

Not much done today, replaced the valuable MVAM108 diodes by brute 1N4007 rectifier diodes. w/o any inductor, the tuning range is now down to 80Hz... now we are getting somewhere. I figure a capacitive trimmer could be used for "set QRG", maybe with a small inductor.
With the new crystal, frequency now reads 3.579793 on the lower edge and 3.579870 on the higher end.
Proposal: color burst qrss from 3.579790 to 3.579890.

by PA1GSJ (noreply@blogger.com) at January 18, 2010 23:33

John Harper, AE5X

ADS-B: Aviation’s APRS

ads-b

Click for larger image

Within the radio hobby, we have not only hams but shortwave listeners, scanner aficionados and many other specialties. And as in ham radio, each category has subcategories – a scanner listener may be interested only in trains. A shortwave listener may only want to listen for commercial RTTY stations.

Those interested in aviation now have another venue available to them that has never before been possible. Until fairly recently, aviation buffs listened to comms on a scanner & enjoyed the routine (and every-so-often, the non-routine) pattern of communications between pilots and air traffic controllers.

That has been the extent of their participation. Until now.

A new technology called ADS-B is on the scene and those interested can see in real-time the locations, ID, speed, heading, altitude and a ton of other data on aircraft within a 100-250 mile radius of the listener’s location.

All commercial aircraft are now fitted with avionic equipment that takes the onboard info (speed, altitude, etc), couples it with the aircraft’s GPS-derived location and then transmits it once per second to ground stations and other aircraft.

As a hobbyist, you can buy everything you need to see the same information aviate- again, in real time – from the comfort of your own home. What you’re buying is a receiver, small antenna and the appropriate software. That’s it.

If you wonder how many aircraft might be within range of you, here is a snapshot of a typical Monday afternoon in the US. Each red dot is an aircraft.

Couple this visual presentation with an airband scanner and now you can hear the pilot whose aircraft you’re seeing on your computer. I’m surrounded by this all day at work and should be jaded by it, yet I can see how this could be a fun past-time for the aviation enthusiast.

The aviation world’s justification for ADS-B has to do with several factors, all compared to radar: economy, precision and coverage. In the US it is mainly used in Alaska and Colorado due to the difficulties of establishing reliable radar coverage in such terrain and in the Gulf of Mexico (serviced out of Houston) to provide air traffic control for helicopters providing service to offshore oil platforms.

But regardless of whether or not ADS-B is used in a particular region, the aircraft overflying that region are equipped and would be observable on the RadarBox. No, I’m not trying to sell these things – just passing along another radio-related aspect of the hobby that others may find interesting. Current price of admission is around $500.

.

.

by John Harper AE5X at January 18, 2010 19:42

Joachim, DL1GSJ

Another Kit for 80m QRSS

Maybe the color burst frequency is really the one to go for. Not only cheap crystals, but also kits are available. And here comes the latest thought: Using the "Warbler" with an audio source, e.g. Eddie's XORgan or some software.
http://smallwonderlabs.com/Warbler.htm
Bonus here, when not in transmit, the Warbler can serve as a grabber receiver.
I would however, for QRSS purposes, pull the local oscillator below the crystal filter. The latter should be slightly differently loaded in order to bring the response somewhat to lower frequencies.

by PA1GSJ (noreply@blogger.com) at January 18, 2010 14:41

Ramsey QRP80C mept conversion update

Keying as originally designed, was a no no, since with both inductors installed, no stable oscillation was obtained at all.
The removal of one of the inductor resulted in stable oscillation but sluggish keying. Tuning range at this stage was about 5kHz.
The only radio-activity I showed today was to remove the second and last inductor of the oscillator. The tuning range is now down to 1kHz, keying is instantaneous.

Up to now I only made use of parts supplied.

by PA1GSJ (noreply@blogger.com) at January 18, 2010 00:19

January 17, 2010

Joachim, DL1GSJ

3 Band QRSS Fireball

This idea is rather old, came back however when playing the 3579.545kHz lately. I feel, it is now the right time to publish it...

You may know about this discontinued kit:
http://www.njqrp.org/fireball40/

Well, in this design, one starts with a 28.322MHz crystal and divides it by two several time by means of flip-flops they could have used a 74LS93 instead and spare one IC). The FB40 reaches the frequencies 28.322 (obviously), 14.161, 7.0805 and 3.54025. All frequencies are in rather busy regions, good for QRP, not so good for QRSS.

Why not doing the same trick with the color burst harmonics? Starting with a 14.31818MHz oscillator, resulting frequencies are 7.15909 and 3.579454. One could also consider to double the frequency, which will get us to 28.63636.
But, because of all this dividing and doubling, FSK is somewhat out of the game. But, in contrast to the original FB40, the available frequencies could be amplified simultaneously, making some three band QRSS operation thinkable: three PAs, three low-passes. From a propagation standpoint, that would be a nice daytime night-time experiment, displaying the opening and closing of the respective bands.

There are cheap crystals and oscillators for 3.579545 and 14.31818, none for 40m however. The 80m and 20m frequencies have been shown suitable in earlier tests.

There is a point in the FB40 which I don't like, the oscillator is keyed. This make the design less suitable for QRSS. Also would I go for one low-pass filter for each band.

In the case I am going to build the 3 band qrss mept, that's what I am going to through together:
  • 20m: oscillator 14.31818MHz, spectral filter by means of a crystal, buffer (keyed) and amplifier (74HC240), low-pass
  • 40m: divide the oscillator frequency by two (7474 or 7493), spectral filtering by Ls and Cs, (keyed) buffer and amplifier (74HC240), low-pass
  • 80m: divide the 40m frequency by two (7474) or use the appropriate division of a counter (7493), spectral filter with a crystal, (keyed) buffer and amplifier (74HC240), low pass
Apparently, the 80m frequencies falls in line with the Ramsey kit QRP80C...

by PA1GSJ (noreply@blogger.com) at January 17, 2010 18:17

John Harper, AE5X

QSLs: New & upcoming developments

AE5XqslThere use to be one way to prove a QSO and it was universal: the QSL card.

I deleted my eQSL account some time ago after questioning why I ever initiated it in the first place since they weren’t valid for awards. That’s changed now as CQ Magazine now accepts eQSL confirmations for its award program. Even better, they will soon be accepting confirmations from the ARRL’s LoTW.

CQ Magazine’s award program is no small deal & their awards are every bit as respected and sought after as those from the ARRL. The two mainstays are the WAZ and Worked All Counties awards. They also have various awards & endorsements for accomplishments in RTTY, VHF and 160-meter operation.

I’m going to reinitiate my eQSL account as soon as I post this. Then the burden become collating paper, LoTW and eQSLs to put together a submission for a given award.

The trouble & effort we go to for convenience!

And speaking of QSLs, I am currently in QSL debt. I’d thought about declaring bankruptcy but scruples kept getting in the way, so I ordered some cards and now face the dreaded secretarial work involved in getting them to their destinations.

Normally I wouldn’t have waited so long but for my last 6 months in W2-Land, I knew I’d be moving – just didn’t know what my address would be, so no use having cards printed.

Then I did move. To an apartment, while house-hunting. That took a while.

And I kept operating all along.

By now we’ve had our home 10 months, the antenna has been up 8 months, the log book is filling up nicely and cards come in via the bureau and even direct (direct from Japan, in one case!).

Those to whom I owe QSLs now number 68. They must wonder if I’ve skipped town and headed across the river into Mexico to escape my debt. Flirting with señoritas and eating pozole. There’s probably a warrant out on me – after all, we all know how rare W5 is.

But no, I’m still north of the border, although I should probably start signing XE/ just to keep the law at bay until my newly-arrived QSLs reach their patiently-awaiting recipients.

If you’re one of those awaiting my card, por favor esperame – la tarjeta esta veniendo pronto!

.

.

by John Harper AE5X at January 17, 2010 12:50

Joachim, DL1GSJ

Ramsey QRP80C first steps

Started the kit. This one seems one deep from the archives. Not only the smell of the components, but also their design I have not experienced in decades! Example: 10k resistor on a strip, pre-bent (!) with a cove in one leg to define insertion depth. Honestly, I should not have used those parts, they are something for musea!

OK, used the parts anyway. This is what I have (not) done so far:

  • ignore all the receiver connection parts
  • build the oscillator (unmodified)
  • test as suggested (result: nothing!!!)
The average builder would have given up at that stage, I believe.
My observation was the following, by slowly ramping up the current limiter of the power supply, suddenly the oscillator comes to life. Extremely unstable however. I figured it may be due to the stone age crystal, so I replaced it with a brand new one. Oscillation now pops in much more easily, however, not within the promoted 5kHz but all over the place. So, pulling is am issue here. After removal of one of the two pulling inductors, the oscillator was alive. No stupid ramping up current starts anymore. So, back in goes the old crystal... no oscillations! Hence, I believe the combination of a (gone) bad crystal and over ambitious pulling is an issue with this kit.

I am curious about the rest of it...

by PA1GSJ (noreply@blogger.com) at January 17, 2010 12:40

Hamsexy dot com

Radio Pirate/Emergency radio jammer taken off the air

Aside from certainly having the rotund body of an amateur radio license holder, the only tunes 14-year-old Jayhaed Saadé will be spinning will be on his daddy’s ipod. After months of ignoring orders from Industry Canada to shut down his 2000 watt transmitter illegally broadcasting his MP3 collection on 91.9 FM, officers from the RCMP and [...]

by admin at January 17, 2010 06:23

January 16, 2010

John Harper, AE5X

PAR OA-50 6m antenna – Installed

oa50My omni-loop antenna for 6 meters arrived in the mail last week – the week of record-breaking low temperatures for Texas and much of the rest of the country. Needless to say, installation was postponed until the Hg eased above the freezing point.

Assembly of the antenna was quick and easy although initially confusing as about a third of the assembly steps had already been completed prior to shipping. The instructions had me looking for bolts to insert as if this hadn’t already been done.

I installed the antenna using a chimney mount and a 5-foot pole. Eventually a 10-foot pole will be used but I’ll first need a longer length of coax before that’ll be possible…

The run to my shack (with 5-foot pole) is 75 feet using RG-213.

Tuning of the antenna is simple and no tools are required. Friction of the elements keeps things in place so well that it is actually a bit difficult to make adjustments. Maybe “difficult” isn’t the right word but a certain amount of effort is required to move the necessary parts. In other words, they’re gonna stay where you put them despite actually having hardware to hold them in place.

Bandwidth (2:1) on my loop is about 850 kHz, which, for this band, is very narrow. Most antennas for 6 meters cover most or all of the band. That’s not very important for my intended use of the band but it may well be for someone else’s.

My main interests on 6 meters are the WSPR frequency (50.293), the calling freq (50.125) and the CW/beacon area just below 50.100 MHz, so the narrow bandwidth of the antenna is irrelevent for me.

Results so far: Nada.

I know long periods of time can go by with nary a peep on this band but next weekend’s ARRL VHF Sweepstakes should generate some workable activity.

Until then, I’ve yet to make my first contact on 6 meters in 32 years in the hobby.

.

.

by John Harper AE5X at January 16, 2010 15:24

Joachim, DL1GSJ

500kHz - SDR crude mod / 500kHz source drifts

The box73 "Einsteiger SDR" for 80m was unused now for a long time. Time to do something with it.
Hence, I grabbed issue 6/2009 of the "Funkamateur" and was looking into the 455kHz mod of the SDR receiver.


This is what I have done so far:
  • replaced the 14.000Mhz oscillator by a 1.843MHz oscillator
  • replaced the tank coil with a 4k7 resistor
This results is no pre-selection at all. OK, a test anyway.
The official mod also replaces sampling capacitors and all inductors for improved performance.


Wired up to the BB6W clone (7m wire + 9:1 balun) and spectrumlab tweak a bit, this is a first snapshot. Not only does this show two WSPR signals, the faint drifting signal at about 502740Hz is the exciter operating at the ground floor of my house, with 30cm of wire at the 7493 Q2 pin. As assumed, a ceramic resonator drifts, and will even spoil the fun when the frequency is divided by 8. (see image below)


Next step, something selective in the front-end, maybe replacing the sampling capacitors...





by PA1GSJ (noreply@blogger.com) at January 16, 2010 02:02

January 15, 2010

Ham Radio QSO Parties

New Mobile QSO Party Software

CQ/X is Mobile Logging Software made by a Mobile Operator.

January 15, 2010 21:28

January 14, 2010

John Harper, AE5X

“The Complete DXer” received – a mini review

w9kniLast week I received The Complete DXer by W9KNI and am happy to report that it was money well-spent.

This is the 3rd edition of Bob Locher’s book and it adds information regarding his QRP DXing endeavors with his new Elecraft K2. Before ordering the book – and the reason I hesistated so long in doing so – was because I was unsure who the book was written for: the guy who is halfway to DXCC or the more experienced DXer who’s been at it a while. I’m at 256 worked and didn’t want to spend time or money reading tidbits that I’d already picked up along the way.

Well, besides being an enjoyable read, this book has two scenarios in it that have made it worth its ownership here. I won’t give away Bob’s strategy but the scenario that’s always put me at a loss with how to deal with it is this: a rare station is not the subject of a pile-up but a participant in one for another station that you don’t need. How do you get the rare DX as he himself is trying to work a station that, for him, is rare?

I’ve run into this scenario a few times and never did get the stations I would like to have in those situations.  I’ll know what to try next time though.

Another part of the book that I found useful was the strategy of tailending during a pile-up. We all know what it is but there is a finesse to it that Bob goes over in detail, adding a few techniques to the process to enhance one’s chances of getting through.

All that and I’m only halfway through the book! I actually wish I’d read this book years ago – it would have abbreviated the learning process and I believe I would have worked several countries earlier than I did as well as having a higher total at this point.

The book also validates something I’ve often felt guilty about. Several times while tuning the bands, I’ve come across pile-ups for rare DX countries that I’ve already worked/confirmed. Yet I jump into the pile-up to work them anyway. I do it for two reasons: it’s a fun challenge with a sense of accomplishment and it hones the skills needed for working the next rare DX that may well be a new one for me. The tinge of guilt I’ve felt at doing this comes from knowing that for many in the pile-up, this is a struggle for a new country and that my presence is decreasing their chances of getting through. But all’s fair in love, war and DXing…

Guilt absolved. Thanks Bob – last night’s pile-up was guilt-free as I worked 5N50K on 40 meters…

To sum it up, this book contains not only useful info that can be put to good use in your DXing, it also contains Bob’s thought process and what led him to develop a given technique. It’s clear that he doesn’t simply go from one new country to another aimlessly – he studies what worked and strategizes along the way, modifying and enhancing what works and rethinking what hasn’t.

All that is shared in The Complete DXer.

Having read the many details of Bob’s DXing experiences, I stand by my previous assertion that most (by far!) of the participants in a pile-up are simply QRMers who have no idea what they’re doing. They’re calling blindly on inappropriate frequencies with their only hope of working the DX being dumb luck.

.

.

by John Harper AE5X at January 14, 2010 18:19

David, VK5DGR

Wifi Phone call using 17mm of PCB track

Yesterday Joel and I performed some simple but effective tests of the Mesh Potato using etched PCB monopole antennas down at Henley Beach. Fancy name for a quarter wave antenna, when etched on PCB at 2.4 GHz this means a 17mm by 3mm PCB track. A part of me still can’t quite accept that phone calls are possible using a 17mm PCB track as an antenna!

by david at January 14, 2010 05:32

Joachim, DL1GSJ

500kHz source update

Added a polystyrene varicap for tuning. Now, setting the range, some experimentation was unavoidable. A 39pF capacitor in series to the ceramic resonators "ground pin" (capacitive divider) to ground resulted in a 500.5kHz to 503kHz tuning range. Maybe replacing the 39pF by a somewhat smaller capacitance will bring the source up by just those couple of 100Hz.

by PA1GSJ (noreply@blogger.com) at January 14, 2010 01:31

January 13, 2010

David, VK5DGR

How not to connect to microstrip

A few days ago I wanted to build some more PCB monopole antennas for testing with the Mesh Potato. This is really easy - you just solder the SMA connectors to the PCB, and add a few bolts. So I built 4 antennas and hooked them up to SWR bridge (described here) to make sure the impedances were OK.

They were all duds - high SWR and clearly not resonant at 2.4GHz. Huh? The first two I built last month worked fine. An hour of head scratching and ill temper followed until I worked it out.

On the recent antennas (top) I had soldered the connector to the front of the PCB, the same side as the microstrip and antenna feed. On the first antennas (bottom) I had (purely by chance) soldered the connector to the rear of the PCB. These antennas worked well.

This is a graphic illustration in how microstrip transmission line works. A transmission line (e.g. an Ethernet cable, television cable, phone cable) transports your signal from one end to the other more or less intact. A regular piece of wire will distort the same signal over any significant distance, for example you can’t use regular wire to connect your TV to your TV antenna.

Transmission line is specially designed for the signal and impedance at the source and load of the line. Mess with the design of the transmission line, and the impedance changes, and your signal gets messed up. For example if you nick or bend your TV cable your picture might get fuzzy as signal is lost part way down the cable.

Microstrip is one way of making transmission line on Printed Circuit Board (PCB). Our monopole PCB antenna contains a length of microstrip transmission line that feeds the signal from the connector to the antenna:

The actual antenna starts where the solid chunk of ground plane (blue) ends. Both the antenna and the transmission line are the same 3mm track. However when you put a ground plane 1.6mm below a 3mm width PCB track on FR4 PCB dielectric you happen to get a 50 ohm transmission line. It’s just like a piece of 50 ohm coax as far as the signal is concerned. Without the ground plane the 3mm track starts radiating (or receiving).

Now placing the connector on the ground plane side of the PCB means the connector doesn’t interfere with the microstrip. Electrically the connector ground becomes part of the ground plane:

However if the connector is placed on the microstrip side we now have a messed up stacking of conductors - we have a conductor at ground potential just above the microstrip track rather than 1.6mm away:

Suddenly the transmission line is not a transmission line any more and the energy being fed into the assembly doesn’t make it to the antenna.

Note in the last picture the microstrip track and connector ground are not electrically connected, as the solder mask insulates them. However the transmission line properties of the microstrip are messed up due to the nearby ground conductor of the connector. I also haven’t illustrated the plated thru hole for the SM connector center pin and matching PCB pad on the ground plane side.

Links

I finally understood transmission lines after reading the chapter from Tony Kuphaldt’s on line book on AC electric circuits. This series of books is excellent and I highly recommend them. I found the link to these books on Mark VandeWettering’s brainwagon blog.

by david at January 13, 2010 23:53

First Mesh Potato Beta Experience

Yesterday I watched Joel set up the first beta Mesh Potato. It’s always interesting to watch some one else work through a familiar task. A good way to tune User Interfaces and documentation.

by david at January 13, 2010 22:50

Joachim, DL1GSJ

500kHz source operative

That's what I soldered together today...

74HCT04 using pins 3 and 4 for the oscillator (1M feedback, 10k damping, 3 legged ceramic resonator), pins  4 and 11 shorted for pulse shaped output on pin 10. Resulting in a 4.023MHz carrier (draaggolf! - now you know what the blog is named after).

SN7493AN: input on pin 14, set to 4 bit (short between pin 1 and 12), pin 10 (!) for GND, pin 5 (!) for +5V and pin 8 for Q2 (divide by 8). Up to now, NOTHING, and that is good!

Keying is done by enabling the ripple counter by grounding either MR1 or MR2 (pins 2 and 3 - inputs of a NAND).
This keying does not produce any audible chirp. At least it did not chirp today ;-)

The near future will add a 74HCT240 as driver and a pulling (FSK) network to the ceramic resonator. Together with an IRF510 HexFET PA, the first attempt of TXing on 600m will be on its' way. Hopefully this will be done by the end of this week!

by PA1GSJ (noreply@blogger.com) at January 13, 2010 10:20

January 12, 2010

Joachim, DL1GSJ

500kHz - using old CB crystals

Some more brainstorming with Jan resulted in the emerge of the idea to use CB crystals for generating a stable signal on 600m.

In an earlier post, I disclosed the use of CB crystals for the 136kHz band. To that time, I mentioned that the same game could be done for the 500kHz band too.
Now that I actually are allowed to transmit on 501 to 504kHz, it is time look into this as well.

In order to get to the 500kHz band, one needs to the divide the 27MHz frequency by 54.
Since CB crystals usually are overtone crystals, we could simply let them oscillate on their fundamental frequency, that would leave us at 9Mhz (gate oscillator / VXO / superVXO). A decade counter (74HC4017) easily divides by 9, which will result in a 1MHz pulse. This pulse is put to a flip-flop generating a nice, symmetric 500kHz signal.

CB (R/C) frequencies that could possibly used in the indicated range:
  • 27.055 / 54 = 0.501018
  • 27.065 / 54 = 0.501204
  • 27.075 / 54 = 0.501389
  • ....
  • 27.205 / 54 = 0.503796
  • 27.215 / 54 = 0.503981
 Let's go soldering!

by PA1GSJ (noreply@blogger.com) at January 12, 2010 18:14

January 11, 2010

Joachim, DL1GSJ

500kHz - easy start revisited

Reaching further in my BOM, I found a 7493, which is a four-bit ripple counter having four flip-flops, so, divide by 8 is no problem.

The present easy start plan consists of an oscillator using one inverter of a 74HC240 as an oscillator with ceramic 4Mhz resonator, pulse shape the signal with a second gate. Divide the output by 8 with the 7493. This should provide a 500Hz signal.

Option 1: The resulting 500Hz signal could be fed into one inverter of the 74HC240 and into two paralleled inverters. The inverted 500Hz signal will be sent through the two further inverters. In this way, I will have made myself a little push-pull arrangement.... NPN-PNP complementary PA...

Option 2: Parallel all remaining gates and use some step-up transformation to a PA's impedance.

Experimental option: Parallel all remaining inverters and directly feed a low-ohmic aerial for QRPp experimenting.

Alternatively, one could use a 7404, here I see two inverters used for the oscillator and pulse shaping, the remaining four gates could be used in parallel.

by PA1GSJ (noreply@blogger.com) at January 11, 2010 23:07

500kHz - subharmonic DC-RX or I/Q-SDR

My earlier mistake (4060) was resulting in the birth of a new idea.

Subharmonic stuff needs the local oscillator of half the operating frequency, so, a rather stable subharmonic local oscillator for 500kHz could be made by using a 4060 ripple counter w/ internal oscillator which divides by 16 at Q4 (pin 7). Sure, in this design, a crystal should be used. I figure this will make a nice and stable local oscillator for a subharmonic direct conversion receiver for the 501 to 504kHz band. Any drift of the crystal will have a 1/8 effect on 500kHz.

Depending on what is going on between 495 and 499kHz, image canceling could be considered.

by PA1GSJ (noreply@blogger.com) at January 11, 2010 21:39

500kHz - easy start

Now that the medium term plans are layed out for the overall 500kHz station, time to have a short time plan for an early kick off.

When browsing the internet, I came across this design:
http://www.alan.melia.btinternet.co.uk/500k_TX.htm
Cool, that's a nice start for an easy concept.

In my BOM (Box Of Materials), 4MHz resonators are present. Using a 74HC4060 ripple counter w/ builtin gate oscillator (Pierce), that should be a really easy start. Either a 4040 ripple counter or three FlipFlops will do the dividing by 8. 4060 was not a good idea, since the smallest division is by 16... Should have checked data books before writing ;-)

Further thinking of a 74HC240 keyed buffer and a IRF510 final.

by PA1GSJ (noreply@blogger.com) at January 11, 2010 21:19

John Harper, AE5X

How to properly brag about your DXing accomplishments

bragIt’s late at night & the rest of your family is asleep. Insomnia has you up and about, conveniently in front of the rig with a small light on. Temps outside are below freezing and the QRN is almost nonexistent.

You take advantage of this confluence of rare circumstances and tune around at the bottom of the 80 meter band. Your tireless devotion to the hobby is rewarded as you copy a stronger-than-you’d-expect CQ from across the Atlantic. It’s a 9L station in Sierra Leone! On 80 meters? Can’t be…..but it is. And best of all, no one’s calling him.

So you hit the memory button on your keyer, sending your call. But he’s listening up & didn’t hear you. A few quick adjustments of your transmit VFO and several calls later, you get him. Just like that, a new country – and a semi-rare one at that – on 80 meters. You’d have been happy to have worked him on 20m, but 80m? Awesome!

Now what? You gonna keep it to yourself? Of course not. That would be anti-social. A mental disorder. What would Freud say about such suppression? So of course you’re gonna tell someone, if only to appease those voices that tell you how harmful it is to keep things bottled up inside. That’s the phrase, isn’t it…..bottled up inside. Musn’t do that, we’re told - it’s bad for us. Causes ulcers & baldness.

So we’re gonna brag tell people about it, if only to maintain our health. And, like the fisherman who repeatedly tells of The Big One he caught, our story is likely to get more and more exaggerated as time goes on if we don’t act responsibly and take certain precautions.

I propose that our precaution be that we cut to the chase. Start the exaggeration right away. People love a good story & they love to be inspired – who are we to disappoint with a mediocre “I worked Sierra Leone” drone? Yawn. Uninspiring.

Here’s whatcha do:

First of all, you worked this guy on the 80 meter band, not the 260 foot band. We’re on the metric system here, so let’s stay on it. Nothing says professionalism like consistency. So when you tell of the pile-up and how long you had to call before finally being heard by the DX station, don’t forget to convert from American to metric. You say you had to call him 10 times? No you didn’t – you called him only six times before he heard you.

This makes the accomplishment more interesting for your listeners and you do them the service of speaking in units they can relate to. No sense in being a xenophobic American with your silly inches, miles and pounds. Step up to the plate and try being a bit more considerate of the customs of others for a change, dammit!

Here’s another example:

You finished CQWW DX contest and your ham buddy is asking how you did. What he really wants to know is, did you do better than him. The fact is, you did rather poorly, what with that Saints-Patriots game and the unexpected in-laws who rudely wanted to visit with you during the contest weekend.

But you ain’t gonna tell your ham buddy all this. Let him have bragging rights over you? No way, Jose. But you can’t lie to the guy either – hell, he means well – he just wants to brag a little too much for his own good. And that’s your department, not his.

So when discussing how many countries you worked (which was, like 8 or 9), simply feign boredom with the whole conversation and drawl out something along the lines of, “Aw hell, conditions what they were, I wasn’t able to work any more than 50 or 52 countries on 80 meters”. You aren’t lying, are ya? But you’re giving the impression that your buddy would be well-advised to come to grips with who he’s dealing with if he wants to discuss DX-prowness with the likes of you.

And he was about to brag about his 30-35 countries worked, which he would have later regretted lording over you. Now, in addition to saving your DX reputation, you’ve also proven yourself to be a fine humanitarian. Always thinking of others, you sentimental old softy

And finally, remember that Sierra Leone station you snagged on 80m? I’ve got great news for you: you effectively worked him on 160 meters! How is that possible? The rig’s freq read-out said we were on 3508 kHz – last I checked, that be the 80-meter band…

Rather than insulting your intelligence, I’ll simply remind you of two phenomena you already know about but have forgotten: Continental drift and Doppler. Nuff said…happy DXing!

.

.

by John Harper AE5X at January 11, 2010 18:13

January 10, 2010

Joachim, DL1GSJ

Update on the 30m Grabber Receiver

OK, the grabber receiver is now receiving successfully since months, I will therefore not change it. Should I build it from scratch now, I would replace the transistor audio stage with one that employs a low noise operational amplifier. In a similar design to the grabber receiver, the 30m Polyakov I/Q-SDR receiver, I used a TL082 dual opamp, needed two channels... I figure a TL081 will do fine for a single channel.
Note, the schematics does not show the supply and ground connections to the op-amp.

by PA1GSJ (noreply@blogger.com) at January 10, 2010 22:14

500kHz - here's the plan

Brainstorming together helps sometimes. Here comes the plan:
  1. build a MEPT for 3500800Hz using a crystal (e.g. from Nick)
  2. build a down-converter using a 3.000MHz standard crystal
Not only allows this concept for dual band operation, it has added value, as one could also down-convert (transvert) signals from a regular transceiver, e.g. FT-817, allowing for WSPR & Co.
When using this in transverter mode, I would go for a 3.000MHz canned oscillator, since no pull is required.

by PA1GSJ (noreply@blogger.com) at January 10, 2010 15:18

500kHz as simple as it gets

We want to reach 501kHz to 504kHz. Here are some easy options, I not sure which one I will go for, depends on the crystals I got in my box.
  1. Subtract 2.000MHz from 2.500MHz => 500kHz obviously.
    This will obviously work with any pair of crystal having a 0.5MHz difference.
  2. Subtract 4.000MHz from 5.000MHz => 1MHz divide by two =>500kHz
    This will obviously work with any pair of crystal having a 1MHz difference.
  3. Subtract 8.000MHz from 10.000MHz => 2MHz divide by four  =>500kHz
    This will obviously work with any pair of crystal having a 2MHz difference.
I agree, one could go further, but, with bigger differences, drift will cancel out less efficiently. The more one divides, the more both oscillators have to be pulled in order to cover the band.


A design could involve the following:
  • Modulated Pierce oscillator for the upper frequency. This oscillator will generate a frequency above the crystals series frequency.
  • Moderately pulled (downwards) VXO for the lower frequency. This oscillator is will set the operating frequency.
  • Dividers, if required, could be FlipFlops.
Now, what's in my box of crystals??

by PA1GSJ (noreply@blogger.com) at January 10, 2010 14:24

500kHz brain storming

Being a part of the early access experimenters group, I am in urgent need of ideas how to become QRV on 500kHz.

Receiving seems no issue: SDR using a 2.048MHz LO (produces a center frequency of 512kHz. Alternatively 4.096MHz and an additional divider... There is an 2.097152MHz oscillator available (Reichelt). Dropping this in the box73 SDR will result in a center of 524.3kHz, well in range with 96k sampling.
RX antenna should also be no deal at all, E-probe etc.

How to transmit?? Hmmm, maybe mixing two standard crystals 2.000MHz and 2.500MHz. Yep, that could be the source. 2.500MHz modulated Pierce, so we get a frequency somewhat higher, and the 2.000MHz as VXO for setting the QRG, pulled down, so less is subtracted. This should get me into the 501-504kHz regime.

Found an idea on the internet, 4.000MHz crystal, divide by 8. This will mean to pull the oscillator between 4.008 and 4.032MHz, now THAT is ambitious.

Now fetching the book "LF Today" from the shelf. Will now read the parts which I skipped in the first place.

Ideas welcome, just send me an email!

by PA1GSJ (noreply@blogger.com) at January 10, 2010 12:29

January 09, 2010

Joachim, DL1GSJ

Ramsey QRP80C considerations

My first awareness of that kit was in 1995, when there was a German supplier for this sort of stuff. I looked at it, and since is was a long way from being spectacular, I forgot about it again. Until recently the search for QRSSable kits started. The manual, which contains all vital information, besides the schematics diagram, can be downloaded from Ramsey electrics' webpage. With all parts listed, block and layout diagrams, it is no problem at all to reverse engineer the schematics; which I did. For reasons of copyrights I will not publish the result however.

As I said, the kit is not really spectacular, that what my understanding of the circuit is:

  • Colpitts xtal oscillator (2N3904)
  • common emitter buffer (2N3053)
  • class C power amplifier (2N3053)
  • crystal pulled by two varactor diodes
  • comes with color burst crystal (3.579545MHz)
In the manual it reads that the oscillator can be pulled 7kHz about the nominal frequency. For 80m I feel that is somewhat ambitious, but can't tell until I have built the kit (just ordered).

There is a switch that toggles between two crystal positions.

Now let's see what can/should be changed:
  1. There is a jumper JMP1 which supplies the tuning potentiometer R1 with 12V. I my view this jumper must be replaced by a voltage stabilizer, such as a 78L08. OK, will provide a little less pull, but should be much more stable.
  2. The oscillator is keyed, OK-ish for QRP, not acceptable for QRSS. Here there are a couple of options, supply the oscillator from the voltage stabilizer and key the PA instead (heavier keying transistor required!), key the buffer only or used FSK only.
    Running the oscillator from the stabilizer:
    Cut the PCB between R5 and R7, run a wire from R1 (tuning pot.) hot end to R7.
    For keying the buffer, nothing will change, since the base of the buffer is pulled up by the keying voltage via R8. If the load change on the oscillator is not too great, this should not be creating too much chirp (to be tested!).
  3. Add some resistor/transistor/what not stuff to supply a tiny bit of FSK voltage to the point where R1, R2 and C1 are joint.
  4. A second crystal could be 3.500MHz or, as soon as there is one, 3.600MHz.
  5. For QRP, the place for the second crystal could be populated with a 3.58MHz ceramic oscillator which will have a much wider pulling range. With a chance of 99.9% I will do this! So there will be one QRSS and one QRP mode for this transmitter.
  6. Also for QRP, two identical crystals could be installed in parallel, this would be a so called "superVXO". The PCB offers sufficient space so that two crystals could easily be installed where only one was once planned.
  7. When no receiver is going to be attached to J2, or RX/TX-toggle is done externally, J2 could serve as an input for the FSK keying. In this case the diode D1 can be replaced by a jumper. The parts L5, R11, L4, D2, R12, R13 and C19 must/can be omitted when D1 is replaced by a jumper.
    I consider that a keying circuit can be build in place of the RX/TX-switching stuff:
    The place of C19 could be used for a 10k resistor connected to the base of a NPN transistor (somewhere close to the tuning pot.). Said transistor could influence in one way or the other the tuning voltage....
  8. The resistor R9, which feeds the buffer, should be increased in order to not overheat the PA transistor in a 100% duty cycle. A trimmer could be added in series to R9 to allow for variable output power.
    Alternatively, a resistor could be wired in series with the choke L3 which feeds the PA transistor.
Those are the mods that came to my mind. There may be more....

Another more general idea: When looking at the parts layout diagram, two pulling inductors are foreseen for the 80m version. For less pull, one could certainly omit one by shorting it (temporarily?), which will allow smoother tuning for QRSS.

Looking forward to receiving the kit!

by PA1GSJ (noreply@blogger.com) at January 09, 2010 17:21

SDR for QRSS

Finally I started building the SoftRock lite 80. This will be serving as a grabber receiver for the upper QRSS frequency (3599900Hz) as well as the color burst frequency (3579545Hz).
In order to allow for those frequencies, I will drop in a 14.285MHz crystal, which I ordered from Rich some time ago. This will result in a center frequency of 3571250Hz, not too far off 3.6MHz and not too close to the color burst frequency either. This receiver, assuming a sample rate of 96k, will be having a range of about 3.523MHz to 3.619MHz.
The original SoftRock lite kit comes with a 20m qrp crystal (14.060MHz), which would allow for the low QRSS range at 3500800Hz and also essentially covers the 80m CW range to about 3.563MHz.
If you think, this is something I want to build myself, yep, it is doable, and it is cheap (see my links). However, this kit involves some SMD soldering, which not everyone is confident doing.

There is an alternative however. Check out my earlier postings when I was writing about the "box73" SDR kit aka SDR Einsteiger-Kit. This kit is also not expensive at all, and it does not involve any SMD parts. Additionally, box73.de offers a hardware kit for the SDR kit, which provides you with an encasing, connectors and a cable to connect the receiver with a soundcard. The "downside"of this kit is, that it employ a canned oscillator of either 14.000MHz or 14.318MHz. The second would be suitable for the upper QRSS frequency, however, the color burst frequency will zero beat. Zero beat will also be the problem with the 14.000MHz version, maybe it will still be suitable for 800Hz, but, this is very close to the LO. I will try this, I ordered and built the 14.000MHz version. One also could imagine to build a clock oscillator with some gates and a crystal, possibly making it switchable....

BTW, most publications speak about a range of +/- 24kHz for such a receiver. This is since a sampling rate of 48k is assumed. With the built in soundcards of the Asus EeeTOP and the MSI Wind NetTop 96k samples are no problem and a bandwidth of nearly +/- 48k about the center frequency can be received.

by PA1GSJ (noreply@blogger.com) at January 09, 2010 15:55

SoftRock lite 80m

The SoftRock lite 80 is up and running. I used a 14.285MHz crystal, so the center frequency is about 3571250Hz. The receiver provides sold copy from 3525kHz to 3615kHz when using a sample rate of 96k.
I assume that the ghost lines about the center frequency's zerobeat line will be reduced as soon as the receiver is in a proper encasing.


by PA1GSJ (noreply@blogger.com) at January 09, 2010 15:43

January 07, 2010

David, VK5DGR

The Amazing Louis Palmer

Last night I went to an excellent talk by Loius Palmer, famous for driving the Solar Taxi around the world in 2007 - 2008. His stories of the trip were very funny and it was just amazing to see what one very motived guy can do. He has also rode the length of Africa by push bike, and flown across the USA at 60 km/hr in an ultralight. An example of a life well lived. If you get a chance to see Louis talk in person or on video I highly recommend it.

He was in Adelaide to help promote the Zero Race, an 80 day race around the world in zero-emission vehicles. In particular the talk was to help our local team entering the race - Team Trev. Trev is a very novel 2 seater car that weighs only 350kg and is assembled from a novel composite material that is simply folded like cardboard. The light weight makes it extremely energy efficient - about 1 cent/km (compared to my EV at about 3 cents/km) for electricity.

Louis has a passion for Electric cars. In particular “solar cars” - electric cars charged by PV arrays on domestic roofs. The key take away was that solar powered EVs like mine are totally possibly today. You should be able to buy a small electric car with a 200km range for $10,000, then run it for free from a $5000 PV solar array. He is puzzled why the big manufacturers don’t get it, and expects the small innovative companies will eat their lunch. I agree.

Louis had some great graphs that showed the big problems with current “green” technologies, like hybrids (glorified petrol cars, excessively complex), biofuels (not enough land in the world), and hydrogen (uses 3 times the electricity/km of battery electric cars). All duds.

He sees China as the best hope in a world naively sailing towards Peak Oil. They lead the world in Solar Cell production and have over 100M electric vehicles (mainly scooters). Australia, on the other hand, leads the world in per-person carbon emissions. Although I am happy to say that South Australia (my state) is getting very close to 20% renewable electricity thanks to a bunch of wind farms going over the last decade. We also have great PV feed-in tarrifs (I get paid 55 cents/kWh for electricity I export to the grid, and pay only 20 cents/kWh for import). Australia also has a pretty good rebate scheme for home PV solar arrays, that cover perhaps $4500 of the typical installation cost.

Louis had some great quotes, for example “if we can afford to bail out banks and big car companies, why can’t we afford to bail out our children?” During his Solar Taxi travels he noticed a lone solar panel on a roof in Canada. He asked the owner, an indigenous Canadian lady, why she had such a panel. She said, “We natives think 3 generations ahead”.

by david at January 07, 2010 22:21

January 06, 2010

Alan Yates, VK2ZAY

Rope Light Controller Failure

Arcing fault destroys the Rope Light controller.

January 06, 2010 03:28

January 05, 2010

John Harper, AE5X

CQ DX Marathon results, antennas and wx

tdwrMy CQ DX Marathon total for 2009 is an even 140.

I didn’t get the dipole up until April, having bought and moved into our house in February. Hopefully next years’ count will be higher due both to having the entire year and, hopefully, better propogation as we move into the next solar cycle. Or at least closer to it.

According to UPS Tracking, my wire and other doodads for my 160m antenna will arrive sometime tomorrow; my 6m OA-50 from PAR Antennas came Saturday.

So mucho antenna work to do and, wouldn’t you know it, the low temperature in Houston for Thursday is 22F. Unheard of in these parts. The high will be 35F. And at work, we just finished alignments on the antenna for a Doppler weather radar. Everywhere, antennas now that it’s cold.

Here’s the break-down by band for the CQ DX Marathon – 100 watts and an open-wire fed 80m dipole at 70 feet:

BAND

DXCC
Countries

ZONES

10

7

7

12

10

6

15

48

21

17

28

13

20

79

24

30

21

15

40

52

24

80

44

17

160

2

2

Total

112

28

 

.

.

by John Harper AE5X at January 05, 2010 04:24

Joachim, DL1GSJ

The ClockMite Transceiver

As the name suggests, this design follows the basic ideas of the RockMite transceiver. It will be, however, more digital...
First ideas are the following. The bag of components will be containing the following
  1. one oscillator for 5.0680MHz
  2. one oscillator for 5.0688MHz
  3. RA3AAE mixer for RX
  4. one XOR-doubler for TX
  5. 74HC4066 switch
  6. 12F629 controller
The doubler and the mixer will ensure operating frequencies of 10.1360MHz and 10.1376MHz, which represents a difference of 1.6kHz (surprise surprise). A 1.6kHz tone is not really pleasant to listen to, I agree, but the simplicity of this transceiver will make up for it.

Both oscillators will be on at all times. Both oscillators are routed (74HC4066) to the active doubler which by default is switched off.

TX: The doubler is switched on only when the transmitter is keyed. The controller will route an oscillator to the doubler and activate the same.

RX: One oscillator is routed to the mixer, preferably via a 5.0688 crystal.

The controller will include a iambic keyer but will also allow for straight keying. A further task of the controller is to toggle between the high and low frequencies.

by PA1GSJ (noreply@blogger.com) at January 05, 2010 02:09

80m QRSS RX, TX or TRX

Some thinking came to my head lately... (ouch!). The 20m + 10.4MHz down conversion is a nice attempt. However, for a quick fix, there is another option.
Wrap your head around this:

TX:
  • 9.600MHz (modulated) oscillator
  • 6.000Mhz down conversion LO

RX:

  • 9.600MHz local oscillator
  • 6.000MHz crystal filter
  • 3.000MHz subharmonic BFO
  • or a 6.000MHz BFO (e.g. w/ NE612)

Now, seeing it, I think 3.5999MHz should be the natural choice anyway, since all crystals involved are off shelf standard....
For reasons of performance I would prefer subharmonic mixing. Simplicity, however, would be found in a single 6MHz oscillator approach.

Hmmm, if only I got the energy to build all my concepts....

by PA1GSJ (noreply@blogger.com) at January 05, 2010 02:05

30m Subharmonic I/Q-SDR Receiver

As promised, some detail about the subharmonic I/Q-SDR receiver. The RX has got a preliminary front end, just for testing, therefore not worth showing. Anyway, some pre-amplification is not that hard to design.


The trick with this design is, to shift the phase by exactly 45 degrees. This is accomplished by the RC combination. Theoretically, a phase shift of 45 degrees is reached when the condition R=XC is fulfilled. I chose a 1k resistor, thus, the capacitor should be 15.6994...pF. Ah well, let's add a trimmer...
For the I/Q-stuff functioning, the levels of both LOs need to be exactly the same, therefore, I added a voltage dividing trimmer to the In-phase path. This trimmer is 2k in order to balance the RC phase shifter.
The total level is adjusted by the trimmer between the oscillator and the filter crystal. This trimmer seems to have a tiny influence on the phase shift...


So, here you got it, the first sneak preview of the 30m I/Q-SDR stuff. See my previous posting for other possible frequencies, most will not have the convenience of a canned oscillator however.

by PA1GSJ (noreply@blogger.com) at January 05, 2010 01:58

David, VK5DGR

Baboons, Mesh networks, and Community

At both Village Telco Workshop I had the pleasure of meeting David Carman and Antoine van Gelder, who founded and now administer the Scarborough Wireless User Group (SWUG). Scarborough is located almost on the southern tip of Africa, on the edge of Cape Town, South Africa.

SWUG uses a mesh network to provide Internet access to people in Scarborough, as DSL is largely unavailable. DSL is connected at one edge of the mesh, and is then distributed throughout Scarborough and some neighboring villages. Users buy their own routers and local youth have been trained to flash and install the routers as mesh nodes.

The mesh network also provides connectivity to those who couldn’t otherwise afford it, and to kids whose parents don’t wish to pay for Internet. The result is wider access which promotes greater community participation in local applications.

Subscription payments are voluntary, with paying traffic prioritized over non-paying. This has worked surprisingly well to ensure that everyone gets access and we are able to afford sufficient bandwidth. The accounting system is fully automated (using bank deposit email notifications), so administration is hands-free and anonymous. The accounting system removes what would otherwise be a serious admin burden. It uses pmacct and changes iptables rules on the fly.

David has installed several communication forums (including phpbb, mediawiki, argwatch). Mailman is most effective. Email is the preferred modality for the naive user and mailman works well for the naive moderator. However the kids on the mesh appear to be using Facebook to organise themselves!

SWUG has lead David and Antoine into some interesting projects.

They have written a very cool application called ArgusWatch to track incursions of Baboons into the community! The Baboons have a habit of sneaking into peoples homes and making a big mess. One thing that fascinates me is how “local” this application is. We are used to most web apps having a global audience. Makes me think there must be many very useful, very local applications that could be written to address local community issues.

David has become skilled at real world mesh network issues like Wifi propagation and is a strong contributor to the Village Telco project. Antoine has been very busy building Afrimesh, a GUI for the Village Telco that is now running on the Mesh Potato. Funny how these community projects change the direction of our lives. I started out messing around with Asterisk on a DSP chip in 2005 and some how I now build Mesh Potatoes!

Talking to David got me thinking about mesh networks and community.

Now a community used to be something local, for example I might get together with other parents from my daughters school and work together to get a school crossing installed. Local people with a common interest working together. A social organization with social aims, compared to say a business organisation that has business goals.

Then the Internet came along and widely dispersed people with common interests could be connected. So now we have widely separated people with a common interest working together. A good example ais the Open Hardware projects I have been working on as part of the Free Telephony Project. Individuals from Canada, China, Bulgaria, Australia working together to develop complex telephony hardware designs. Together we built leading edge IP-PBX technology - as good or better than products coming from giant hardware companies. One example is the BlackfinOne - a community built open hardware Linux board, forerunner to the IP04:

Mesh networks close the circle. A mesh network depends on neighbors working together. My Internet comes via my neighbor’s router. There is a dependency that encourages people to work together and help each other (even if only by leaving their router on). So just like the first example we have local people working together, but this time facilitated by Internet technology. SWUG is a social enterprise that outperforms the incumbent Telco in delivery of broadband to the people of Scarborough.

In my travels to East Timor I found an interesting counter-example. East Timor has very little local Internet infrastructure and very little local content. Most of the Internet traffic goes straight up a satellite dish to ISPs in other countries. I found no examples of IP traffic going from a browser to a web server in East Timor - it all left the country as a first step. As you can image the cost of accessing information on the Internet is prohibitive ($5-10/hour where people would be lucky to earn that in a week). I wonder what that does to a community?

Thanks

Thanks David Carman for checking this post and providing additional details of SWUG.

by david at January 05, 2010 00:39

January 04, 2010

Joachim, DL1GSJ

Subharmonic SDR RX (TX?)

I still have not published any details about my subharmonic, yes, subharmonic, SDR receiver for 30m. Will come, I will tackle the diagram drawing later that day. So much is said, take a subharmonic local oscillator, split the signal in a I and a Q paths and delay (phase shift) the Q path by 45 degrees. Yes, it works, the 30m version really works, image canceling and everything.
30m is based on a 5.0688MHz canned oscillator.
Unfortunately, I could not find anything for 12m...

Here come the ideas for other bands:
Frequencies in MHz, the crystals for frequencies printed in italics are available at box73.de

80m
  • DATA/Voice - 1.800
  • Voice - 1.820, 1.856

40m
  • DATA/Voice - 3.535
  • Voice - 3.560, 3.579

20m
  • CW-range - 7.015
  • DATA - 7.030
  • Voice - 7.058, 7.122

17m (overtone CB crystals => divide by three)
  • best fit: 27.155, 27.165, 27.175, 27.185, 27.205

15m
  • Voice/SAT - 10.700

10m:
  • CW - 14.010
  • DATA - 14.055, 14.058, 14.060
  • Voice/SSTV - 14.200
  • Voice - 14.250, 14.252, 14.270, 14.285, 14.300, 14.318, 14.333
  • SAT - 14.7456

Some other options could be considered:

SW-BC
  • 75m - 2.000
  • 60m - 2.4576, 2.500
  • 49m - 3.000, 3.072
  • 31m - 4.9152
  • 25m - 6.000
  • 16m - 8.8672
  • 11m - 12.750

Weather FAX
  • DDH - 3.9321
  • GYA - 4.000
  • NMF - 2.97152

Weather TTY
  • Hamburg - 5.0688

SW-Navtex
  • 2.97152

It needs to be mentioned that the L.O. should put out a pure sine wave. The easiest way to achieve this is a crystal as a filter, as I did it in my 30m subharmonic direct conversion receiver. It seems tempting to use counters & co to reach more frequencies, but, the amount of filtering required would spoil the simple design...

by PA1GSJ (noreply@blogger.com) at January 04, 2010 15:13

John Harper, AE5X

New words for a new decade in ham radio

morsecodepink

Morse Code Pink

Welcome to 2010!

Inspired by the creative mind over at The People’s Cube – new words definitely likely possibly coming into our rich ham radio jargon…

More are likely to be added over time…

 

 

 

 

 

 

  • Contesticles – body part responsible for giving one the fortitude to endure 48 hours of rote, non-stop, repetitive exchanges of trivial information 
  • Dela-nowhere – an imaginary state in W3-land that, despite its fictional status, is nonetheless required in order to achieve ARRL’s WAS award.
  • Dipolarized – the process of having been divided into two camps, each believing their own term is the correct one for a certain antenna – dipole or doublet
  • Hertz – that pain you feel when you touch an AC-energized electrical component
  • Morse Code Pink – an organization devoted to eliminating CW as an amateur radio communications mode
  • Mutual Outductance - electrical characteristic displayed by a torroidal transformer with one winding wound in the improper sense (DOH!)
  • QRPrection – that exciting male-only event that occurs when a new low-powered radio kit is announced
  • Radiofactive – said of one who speaks knowledgably of wireless communications
  • SDR Radio – “Some Don’t Read-Radio”, the non-communicative type of radio practiced when you try to get Rocky and a software-defined radio to work with Windows Vista, learning later that the manual clearly states that it is incompatible with that O/S
  • Shamateur Radio – echo-link and other radio-free modes of communication
  • WhisperNyet – the process of loudly proclaiming your WSPR accomplishments on WSPRnet.org and other blogs

.

.

by John Harper AE5X at January 04, 2010 03:49

January 03, 2010

Joachim, DL1GSJ

80m MEPT update

A little progress on the 3599900Hz MEPT, I got the 5200500Hz local oscillator running.

Changed the plans in the progress, the second half of the 74HCT240 is now dedicated to the local oscillator and maybe a buffer stage for the 80m signal. The plan to use it as 20m driver is dropped.

Further steps, use a voltage divider to adjust the mixer drive level, couple out a tiny amount of 14MHz signal, build a 4MHz low pass and feed the result into the remaining inverters.

by PA1GSJ (noreply@blogger.com) at January 03, 2010 17:40

John Harper, AE5X

A new kit coming soon – for 80 meters

80mkitIt’s nice to see a kit about to be offered for something other than the 20-30-40 meter bands. This one is an 80m transceiver for what looks to be a bargain price of $50.

Details of the kit are on the Azscqrpion’s website.

Yep – I”ll be buying one.

There’s a Yahoo Group here (of course) with more info, photos, Q&A – the whole 9 yards (8.23m).

Get ready for some serious torroid-winding; none of that 10- or 18-turn stuff common on 20-40m rigs…

.

.

by John Harper AE5X at January 03, 2010 01:26

January 02, 2010

Joachim, DL1GSJ

QRSS TRXs for 40m and 20m

Cheap single channel QRSS gear
With my 30m d.c.-receiver now running successfully for months, it would be time, I though, to "design" dedicated receivers (transmitters) for some more bands. The basic idea will follow the 30m-Polyakov design, just not using a canned oscillator this time. (for the schematics, please have a look at my web-page http://www.qsl.net/dl1gsj/).

40m version 1 (7059,9kHz)
Jan's comment on my 40m RX ideas brought me to the conclusion, that it would be desirable to use 3.530MHz crystals for a Polyakov receiver, additionally, with a slightly different pull, the same oscillator could be used in a transmitter design with a frequency doubler. When going for an active doubler, it could be switched off, so no carrier will be present during RX.
The downside, no side-band filter, which, in this portion of the band, seems crucial to me.
There is hope however, Rich offers a 7.058MHz crystal, which could be used as a notch filter in such a receiver.

20m version 1 (14096kHz)
Rich also sells a crystal 7.050MHz, this could be used in a similar fashion as mentioned above for the alternative 20m frequency. Even having the same side-band problem as the above idea bit no obvious solution to it. One could consider to receive in LSB such that the USB will be on the IBP-beacons, which could be an interesting addition...
Probably a superhet-RX with 10Mhz and 4.096MHz crystals would be the safer bet here; alternatively: 18.096MHz and 4.000MHz. In such a RX-TX combination, all oscillators could run the whole time.

40m version 2 (7000,8kHz)
Nick offers crystals for 3.500MHz, which make wonderful subharmonic local oscillators for 7000.8kHz. Additionally, there would be a 7.000MHz crystal available at box73.de, which could be used as a sideband filter, even though, I think, that 6999.2kHz would not be that crowded. Again, the L.O. could be used with an active doubler for TX....

20m version 2 (14000.8kHz)
As stated before, there is a 7.000MHz crystal available. Now, same concept as for the second version 40m. With a 14.000MHz crystal available (conrad), one could image a side-band filter... but, what will be on 13999.2kHz?

Conclusions
Seems that some crystals will have to be ordered in Florida, since 7059900Hz has priority with me and all crystals are available from one source.
Since no canned oscillators are available for, the idea would be a classic approach using transistors, hence no L.O.-xtal-filter, as in my 30m design, will be required.

Prospects
I have not tried it yet, but it sits on my workbench (30m version) quite some while now, using the subharmonic mixer in reverse for generating a DSB signal. With either passband or notch filters, a single side-band signal could be generated, just like in Gene Marcus' design of a 30m WSPR TRX. Could be used with an XORgan ;-)

by PA1GSJ (noreply@blogger.com) at January 02, 2010 21:15

Steve, WG0AT, ex N0TU

January 01, 2010

Hamsexy dot com

Hamsexy Colt: update

Hamsexy reader Rodney sent us this email in response to our posting earlier this day (see below) on the Radioactive Colt: This ham whacker mobile belongs to one of the members of the Jupiter, FL ham club…notice this “ghetto glider” being touted in a parade, nice. Nothing like this to represent ham radio. I am sure [...]

by admin at January 01, 2010 20:52

Hamsexy Colt…. we did it already

We’ve gotten a metric assload of emails from people urging us to do a write-up on the ‘Radioactive’ Dodge Colt crammed full of radios that was featured on Jalopnik last month. Here’s the sample: We would, but we featured it on this very site back in April of last year.

by admin at January 01, 2010 17:23

December 31, 2009

John Harper, AE5X

Yesteryear in radiotelegraphy – audio

Shipboard wireless room - 1912

Shipboard wireless room - 1912

From Phillip’s & McBride’s frantic CQD/SOS sent from the sinking Titanic right up to the bitter end of the 20th century, shipboard radio operators routinely sent dots and dashes flying across oceans.

All that eventually got replaced by INMARSAT and other services, but at this time of year it’s traditional and fun to remember the way things were once upon a time.

I don’t know who made this recording and I’m not the one narrarating it but it got a lot of hits and downloads from my site before I moved it to this blog format so here it is again, a recording of 500 kc shipboard traffic from 1974.

 

From the first 1/3 of the recording I can pick out callsigns EAS, ZDK, OXZ, EAL, EAF, FFM OZB and ZXA but I’ve missed quite a few.

As said in telegraphy even today ”HNY es 73″

.

.

by John Harper AE5X at December 31, 2009 15:46

December 30, 2009

John Harper, AE5X

Goodbye to the old 3-meter band?

"Captain, I'm not picking up any signals in the old 88-108 MHz band, but I love this new Bluetooth."

Or to non-hams, the FM broadcast band. The writing is on the wall.

Not long ago, I discovered Pandora.com and it was love at first listen. I type in a few singers I like - John Hiatt, Mark Knopfler, Moody Blues, Chris Isaak – and then tell Pandora to play music similar to the music these guys have produced and before you know it, I’m hearing great music by individuals and groups I’d never heard of…and would never have heard of if my available music was restricted to local radio stations.

Now I’m a fan of the Bodeans, David Gray, The Jayhawks, Nick Lowe, Richard Shindell, the Notting Hillbillies…..well, you get the idea.

To hear all this, I had to be tied to the ‘puter. But no more. A LogiTech daltowSqueezebox has taken up residence here and now the world is at our fingertips, wirelessly and QRN- and QSB-free. Pandora is still there plus a ton of other stuff.

(I wonder if Daltry and Townsend have a Squeezebox…..Who? No, THE Who…oh, nevermind)

Unfortunately, all this great music is unavailable to me when I’m on the road unless I burn it to a CD or play my wife’s iPod through the car’s stereo. It’s still recorded music either way.

But an article in Monitoring Times tells me that the new generation of iPhones and Microsoft’s Zune can stream HD music right to your car’s auxilliary audio input jack filling your car not only with music but, like Pandora, with music of the type that you actually like.

Ford and Microsoft are teaming together to create Sync, a stream-capable voice-activated computer built into your dashboard for navigation, cellular calls and streaming music.

chrysler_wifiChrysler is working on something similar and, although the infrastructure isn’t there yet to allow every driver on a given highway to have his own individual streaming connection – an issue of bandwidth - demand often drives technology, as it eventually will in this case.

These are the preliminary baby steps of course but technology of this nature advances to maturity in record time. Two or three years from now it may well be common-place to be able to take a multi-state road trip and listen to music tailor-made to your ear for the entire trip. And sqzbxfive years from now, there may be no further use for the FM broadcast frequencies.

And speaking of frequency vacancies, with the demise of international shortwave broadcasting, I can’t help but wonder who will end up getting those shortwave freqs?

Sadly, most SW broadcast stations still on the air are of a religious nature. The major broadcasters of yesteryear have gone online to stream their broadcasts. Even BBC to the US is no longer aired. They had a ton of freqs alotted to them – I wonder what will become of them.

I know what I’d like to see happen to them…

.

.

by John Harper AE5X at December 30, 2009 22:04

December 29, 2009

John Harper, AE5X

CQ DX Marathon

CQDXmarathonThe end of the 2009 CQ DX Marathon is two days away and coincides with the beginning of the 2010 CQ DX Marathon.

This is an interesting event in part because WARC bands are fair hunting grounds.

Another interesting aspect is that one of the categories is for indoor-only antennas. So if you’re operating stealth with an attic antenna and have given up on the idea of participating in any of the DX contests, take heart – you’ll only be competing against others similarly equipped.

In 2008, the winner of the Indoor Antenna category worked 124 countries and 28 zones. In a single year. The runner-up worked 121 countries and 33 zones. Not bad at all.

In the Unlimited category, W9KNI worked all 40 zones and 288 countries. More countries in a single year than I’ve worked in 31 years! And in this part of the solar cycle no less. By the way, W9KNI is the author of The Complete DXer. I guess he knows what he’s talking about.

I didn’t go about 2009 thinking of this event – in fact, I only found out about it recently but plan to submit my results anyway. Easy enough to do with electronic logging. Scoring is simple: Number of countries worked + number of zones worked. No multipliers. And any mode, even PSK31 ;-)

Although I don’t have my current logs here on my laptop, I see that as of last month I’d worked 81 countries and 27 zones in 2009 for a score of 108.

Submission is made via an Excel scoresheet made easy and darn-near automatic by AD1C as long as your logging program can export an adif file.

I like that the WARC bands are considered and that the event is all mode inclusive. If you’re active on HF, you’re in.

by John Harper AE5X at December 29, 2009 23:16

Steve Nichols, G0KYA

Propagation charts for January 2010


I have been experimenting with HamCap. It uses the VOACap engine to produce propagation maps and charts. As an experiment I have created a series of band-by-hour charts for the UK - now updaetd for January 2010.

These are based on 100W to a dipole at 35ft, with a smoothed sunspot number of 17. They are all short path too. You can try them here.

I think that 20m looks a bit optimistic with propagation way after sunset - time will tell!

by Steve Nichols (noreply@blogger.com) at December 29, 2009 08:36

December 28, 2009

John Harper, AE5X

The cost of a hobby & the best deals in ham radio today

dollarMany years ago, a high school friend and I decided to get into scuba diving. We took lessons, rented equipment and dove those muddy lakes in East Texas. Its a wonder we didn’t get bitten by water moccasins like that Irish kid in Lonesome Dove. Years later, the Navy took me to real places for divers: Guam, the Philippines, Thailand, VQ9, VK6. But while my transportation to these places may have been free, the requisite equipment wasn’t.

Today, a modest scuba set-up easily tops $1000. And that doesn’t include transportation to a worthwhile site.

How about photography as a hobby? Good D-SLRs can now be had for $500 or so, but accessories will quickly push that to the kilobuck level and beyond. And accessories are needed for all but snapshots.

Motorcycling? Another expensive hobby. Ditto for radio-control stuff, trains, car restoration, computers, hang-gliding, skydiving, amateur astronomy, backpacking, etc.

So when people piss & moan about how expensive it is to get into ham radio, I take it for what it is: a BS excuse. Expensive compared to what – knitting? Yakking on 2m FM with your JingTong?

For less than $500, a DX-working HF station can be put on the air in a variety of modes. That assumes you already own a computer, and who doesn’t?

And if you don’t even want to spend $500, here are the best deals in ham radio today:

Unlike a lot of hobbies, ham radio doesn’t have to be expensive. And at my house, it ain’t!

However there are a LOT of rip-offs in ham radio. That’ll be another post.

.

.

by John Harper AE5X at December 28, 2009 23:59

Alan Yates, VK2ZAY

4-channel PWM Tree Emulator

A web-based emulator for the 240 LED Christmas Tree project.

December 28, 2009 15:28

David, VK5DGR

Electric Car BMS Controller

This post is about a Battery Management System (BMS) Controller that I have designed, built and tested for the Lithium batteries in my Electric Car. I recently installed some SkyEnergy Lithium batteries in my EV. Lithium batteries are sensitive to overcharge and undercharge so some sort of Battery Management System (BMS) is required.

A BMS Controller (aka BMS Master Unit) disconnects the chargers when the batteries are full and warns you when they are empty. For a bit of fun I designed most of the logic using transistors and diodes rather than using a microcontroller or regular logic chips. It has been designed on fail-safe principles to best protect my expensive new Lithium battery pack.

The BMS controller works with BMS modules that sit on every cell. I use the CM090 BMS modules from EV Works. Here is a photo of 4 of the BMS modules installed on 4 cells:

The BMS modules are the red PCBs with the components in translucent plastic. Note the thin blue wire connecting each module. This wires snakes through every one of the 36 BMS modules and forms a “dead mans switch” normally closed loop. If any one of the modules detects an over volt (4.1V) or under volt (2.5V) condition it opens the loop. The BMS Controller then does something sensible with this open loop information. When charging this means stop charging. When driving this means stop driving. Otherwise you can kill your cells or in the worst case even start a fire.

Every cells is slightly different, so you need one BMS module per cell. The BMS modules also function as series regulators. As the cell reaches 3.6V during charging the BMS module starts bypassing some of the charge current. This helps bring all cells to a similar state of charge.

Re-cycling Lead Acid Chargers

Now most people installing Lithium batteries would go out and buy a commercial BMS controller and a suitable charger for their battery pack. However I made a promise to my long suffering, EV supporting (and EV-driving) wife that the entire Lead-acid to Lithium conversion would cost no more than $6,500, which was about the cost of the Lithium cells and CM090 BMS modules.

That meant I had to re-cycle the chargers I had laying around, which amounted to a 96V (8 by 12V) AGM charger and a bunch of 12V dual-stage Jaycar M-3612 chargers. Lead acid chargers usually charge to around 14.7V per 12V battery. So the AGM charger that is rated at 96V actually charges to around (96/12)(14.7) = 117.6V.

I ordered 36 Lithium cells which have a nominal voltage of 3.2V. After some reading and a few emails to the helpful EV-works guys I determined that the Lithium cells are just about fully charged at 3.6V. So we need a charger (or chargers) capable of a total of 36(3.6)=129.6V.

This just happens to break down nicely to the AGM charger (117.6V) plus one 12V charger. However each charger will charge at a different rate. So this means I need two BMS Controllers, one for the 32 cells connected to the AGM charger, and one for the 4 cells connected to the 12V charger. Each would have a separate loop of BMS cell modules to monitor.

BMS Controller Requirements

I came up with these requirements for the BMS Controller:

  1. During charging independent monitoring and cut off of the two BMS module loops.
  2. When driving sound a buzzer if we get a low voltage situation. This buzzer shouldn’t fire when charging. I like the idea of an annoying buzzer. My wife was quite good at “driving through” visual warnings of low batteries with my lead acid pack!
  3. When a BMS module loop opens charger power should be cut and stay cut. It shouldn’t start charging again if the cell voltage drops (which they do just after charging), as I don’t want the whole system cycling off and on all night.
  4. It should handle up to 100 ohms of loop resistance from the series connected CM090 BMS modules.
  5. It shouldn’t draw significant power from the car’s battery pack or 12V battery when not in use.

Analog versus Microcontroller

Many people have developed Lithium BMS systems. An obvious choice for each cell module is a little microcontroller that communicates with it’s peers using some sort of serial bus. Then as well as BMS functions you could report the voltage and temperature of each cell, and do all sorts of other magic. The EV Works guys have taken the KISS approach and used an analog design, which I guess is a bunch of voltage references and comparators plus a big transistor to dump the heat during series regulation. They argue that in the heavy duty EMI environment of an EV it’s too easy to crash a microcontroller and screw up digital communications. Software can also be a source of problems. Would be a bummer to set instead of reset a bit and burn down your garage from an overcharge fire.

I have experienced EMI problems in my EV - my microcontroller based voltmeter/ammeter instrumentation goes nuts when I accelerate and often resets itself while I drive.

However there are plenty of cases where microcontrollers have worked for years in high EMI environments. For example a petrol car’s fuel injection computer operates just fine while located a few inches away from a 10kV spark ignition system. So I think the analog idea has some merit and is likely to have less bugs and be easier to develop, although I wouldn’t rule out microcontrollers. Using analog instead of a microcontroller also has a kind of retro appeal.

So I decided to try using transistor and diode logic, and no microcontrollers. I almost got away with it, too.

State Machine

I like state machines, they are a relatively error-free way of designing complex logic. I use them widely in software and hardware projects. This project needs a simple state machine, but the implementation (using discretes) is complex. So before heating up the soldering iron it’s a good idea to have a very clear idea about the logic. This approach let me break down the circuit into clear logic blocks (flip flop, inverter, diode gates), each that was implemented as a separate chunk of hardware. Divide and conquer.

When power is applied we start charging (CHARGE State), and any break in the BMS module loop causes us to switch off the charger (OFF state). Once we have switched off we stay off, no matter what happens to the loop. Two states can be expressed with a 1 bit flip flop, which brings us to the schematic.

Schematic description

Here is the BMS controller schematic PDF. I also have the gschem files if anyone wants them.

There are two BMS Controllers, one for each loop. The BMS LOOP2 Controller at the bottom is the easiest to understand. Q6 and Q7 form a Set-Reset flip-flop. You pull the base of Q6 low to set the flip flop, and the base of Q7 is taken low to reset the flip flop. When power is applied, C6 sets the flip flop, putting it in the CHARGE state. Led D12 lights when the flip-flip is set (CHARGE state).

When the flip flop is set, the collector of Q7 is close to 0V. This pulls the base of Q9 low via D18 and R22, allowing current to flow through the relay that controls the AC power for the LOOP2 charger.

Note that the relay current flows through the BMS module loop. This is an extra layer of safety - even if the flip flop gets stuck on, if any of the BMS modules open the loop then charging will stop. The BMS modules can handle 100mA and the relays chosen use 70mA. A fuse in the BMS cell module loop is a good idea.

When the BMS module SLOOP2 opens R19 pulls the base of Q8 high which causes Q8 to switch on. The collector drops to near 0V and pulls the base of Q7 low via D13, resetting the discrete flip flop. The system is now in the OFF state and even if SLOOP2 closes again power to the relay and hence charging will be disabled.

D14 and D15 in the base circuit of Q8 make sure that Q8 stays off when nominal currents are flowing from the relay circuit through RLOOP2. For LOOP1 (32 BMS modules) RLOOP1 was measured at 20.5V, with 70mA flowing 1.4V is induced, enough to switch on Q8 if D14 and D15 weren’t present.

I built the first version using a piece of PCB with squares cut using a Dremel:

But this soon became unwieldy and I was concerned about shorts. So I rebuilt it using veroboard which was neater and I hope more reliable in the long term:

The left hand side controls the AGM charger, the right hand the 12V charger. Only one side would be needed for a single charger. The electronic parts total just a few $, the relays are probably the most expensive part.

This board was mounted in a plastic box with the relays, AC power sockets, terminal strips etc. Crimped automotive lug-type connectors connect the BMS Controller with the sense loops in the car, 12V ignition power, and car ground. These connectors can be removed in a few seconds so I can take the BMS Controller inside to mess with it. Until recently, this happened a lot!

Taming a too-smart AGM charger

The BMS LOOP1 controller is a little more complex. After trying the BMS controller I noticed the AGM charger would stop charging after about 90 minutes with a “battery error” warning. I think this is because of the different charge characteristics of Lithium batteries compared to lead acid. Lithium cells seem to charge very slowly between 3.3 and 3.4V until very near the end of the charge. For example a cell might remain at 3.34V for hours while it charges. The voltage of a lead acid pack moves more linearly as a the pack charges, unless the pack has dead cells in it. My AGM charger is “smart” and thought it had a lead-acid pack with dud cells. So it stopped charging and raised an alarm.

The AGM charger could be reset by power cycling it, so I included a timer to do just that. What I needed was an oscillator with an on time of 90 minutes and an off time of 30 seconds. I looked around for an analog design but chips like the NE555 are limited to a few 10’s of minutes due to analog effects like capacitor leakage. So I relaxed my analog-only approach and used a PIC microcontroller, here is the PIC source code.

In the BMS LOOP1 circuit D9, D10 and R12 form a two-input AND gate, ensuring the AGM charger (Charger 1) is only turned on when both the PIC timer output and flip flop are set. Diode AND gates effectively clamp the “low” voltage to 0.6V, so D8 ensures the base of Q4 is less than 0.6V keeping Q6 off.

BTW it is really, really important not to confuse the SLOOP1 and SLOOP2 wires when installing in the car - we don’t want the wrong charger switching off!

Drive Mode

The schematic discussion above deals with Charge Mode, where the idea is to stop charging when the BMS modules open the BMS loop due to one of the cells being over 4.1V. In Drive mode, the BMS module loop opens when any cell drops beneath 2.5V. This will probably happen during acceleration with nearly-flat cells, due to the internal resistance of the cells.

In Drive Mode we don’t want the flip flop or relays to be active, we just want to sound a buzzer when either SLOOP1 or SLOOP2 opens. So in Drive Mode we just power the inverter circuits (Q3 and Q8). Diodes such as D19, D22, D21, D1, D6 and D20 isolate the Drive Mode circuit from the Charge mode circuit.

In Charge Mode the circuit is powered from a 12V plug pack. In Drive Mode the 12V “Ignition” rail from the car powers the circuit. This ensures there is no drain on the cars traction or accessory battery when we are not driving. The “Ignition” circuit is just the 12V rail of the car that becomes active when you switch the ignition key to “On”. The term “Ignition” is a bit of a misnomer in an EV but you get the idea.

Testing and Development

I developed the BMS Controller circuit over a few weeks as a pleasant part time activity. At first I didn’t pass the relay current through the loop, I had it wired in the collector lead of the flip-flop Q2. However one day I had a near-death experience where I had somehow zapped Q3 without knowing so the flip-flop never flopped into the OFF state. Luckily I was monitoring the batteries at the time and no damage was done. However it convinced me to add the redundancy of passing the relay current through the BMS module loop.

Initially I had the AGM charger connected to 32 cells and one 12V charger connected to 4 cells. However I noticed that the AGM charger took much longer to finish the charge. The reason was the current from the AGM charger was only 7A, compared to about 12A from the 12V chargers. With 32 cells the AGM charger was seeing about 32(3.3) = 105.6V so it was “tapering” the charge current to the lead acid cells it thought it was charging. So I tried connecting the AGM charger to 28 cells and added another 12V charger. This brought the AGM charger current up to about 10.5A - much better. The 2nd 12V charger was added to the LOOP2 circuit, as I reasoned that identical 12V chargers charge at about the same rate.

The only problem with running the AGM charger on just 28 cells is that it doesn’t taper the current towards the end of the charge. The series regulators in the BMS modules have only limited bypass capability (700mA) so for effective equalisation we would like a final charge current of just a few A. I’ll need to watch that over time, to see if the cells drift apart in state-of-charge. A proper Lithium charger would be adjusted to taper the current off the whole pack to a point where the BMS modules could effectively equalise on every charge.

Here are the chargers mounted in the back of the EV. Just two were mounted when this photo was taken:

And a close up looking down on the (three) chargers:

Jaycar MB-3612 Charger and Lithiums

The low cost 12V lead-acid chargers I have used are really well suited to blocks of 4 Lithium cells. Curiously, these chargers work better for Lithium cells than for the lead acid batteries that they are designed for (see EV Bugs post)!

These chargers have a simple two-stage tapered current design. When the voltage they see is close to 12V, they charge at about 12A. As the lead acid battery charges and the terminal voltage rises this drops linearly to a few A as the battery reaches 14.7V, which results in rather slow charging and no equalisation for lead-acid batteries.

However this profile just happens to be very good for Lithiums. My Lithuim cells stick to around 3.2-3.3V for most of the charge (hours), then they quickly shoot up to 3.6V (plus) in the last 20 minutes. However as the voltage rises, the MB3612 tapers it’s current off. This allows the BMS module series regulators to shunt current around cells that are a little ahead of the curve. The result is the over voltage cut out never fires for the 12V chargers, and the cells are always nicely equalised. I guess the small number of cells under each charger (just 4 per charger) also helps.

In practice the LOOP2 controller never switches to the OFF state, as the 12V chargers stop charging before any one Lithium cell reaches 4.1V. The LOOP1 AGM BMS controller always switches to the OFF state, as one of the 28 cells charges a little earlier than the others. The lack of tapering of the charge current means full charge current is applied right to the end, when the 28 cells are at about 101V.

Note: my MB-3612 12V chargers have been modified to allow series-string connection (removed ground wire from negative lead, making the output fully floating), and tweaked to charge to 14.7V instead of the rather low 14.1V they were initially set to (trim-pot in middle of PCB).

Next Steps

The BMS controller has been working nicely since I put the Lithium-powered EV on the road 2 weeks ago. Next I would like to design a PIC or Atmel based voltmeter/ammeter/Ah meter. As you can see I enjoy messing with electronics and the EV, so I am just looking for an excuse to build some of my own instrumentation.

An Amp-Hour counter would be really useful for Lithiums as they are not afflicted by the Puerkert effect like lead acid batteries. This would make a AH counter a really useful indicator of “fuel” remaining.

Thanks

Thanks Mithro for lending me his PIC programmer and PIC collection when he migrated to Sydney - has been very useful for this and a few other PIC projects.

Links

Lithium Batteries for my EV - converting my EV from lead acid to Lithium
David’s EV Page
EV Bugs Post

by david at December 28, 2009 00:27

Lithium Batteries for my EV

Over the last month I have been installing a pack of SkyEnergy Lithium cells in my EV. I like working on my EV. Gets my out of the office and I enjoy the mechanical side, especially welding. A pleasant way to spend a few hours a day.

There has been a cool side effect from working on my Electric Car. Since I started this EV project 2 years ago there has been a steady improvement in my mechanical skills. I feel capable of handling other mechanical jobs that previously would have intimidated me. When I hit a tough problem I say, “Well, if I can build an Electric Car, then how hard can this be……..”.

In this post I will talk about my Lithium battery rack construction, as this might be useful to other people contemplating their own conversion. I certainly found the battery racks a major challenge when I started my EV project, but of course it depends on your skill level.

The main reason for the Lithium conversion is the long life cycle of Lithium cells (3000 cycles plus, or perhaps 10 years). We have done about 10,000 km on lead-acid batteries, and they were a fine way to get started with EVs. However with the natural drop in new technology prices and the high Australian dollar Lithium packs have dropped in cost by 50% over the last two years. So it was time for us to take the plunge.

Out with the old:

In with the new:

Lie, Damn Lies, and the Range of EVs

I had a firm budget from my wife for the Lithium conversion that I was determined to stick to. So I decided to buy 36 100Ah cells. These have a nominal voltage of 3.2V so this gives us a capacity of 36(3.2)(100) = 11.5kWh. Cruising at 60 km/hr my EV uses about 5kW so this suggests a range of (11.5/5)(60) = 138 km. Hmmmm. One thing I have learned about EVs is that there are lies, damn lies, and EV ranges.

In the real world many factors reduce the practical range on an EV:

  1. In real world driving we need to stop and start a lot. Acceleration uses a lot more energy than cruising, for example normal acceleration to 60 km/hr requires 15kW in my car. Higher currents have higher resistive losses. I do recover some of this energy back, for example when I see a red light I coast the last couple of hundred meters, using 0 energy (try that in your carbon-burner that must idle all the time).
  2. Each of the cells in a battery pack are slightly different. Somewhere in there is the “weakest cell”. When any one cell in the pack is discharged you must stop driving. Passing current through a discharged cell will kill it. As all of cells are wired in series when this weakest cell is discharged thats the end of your driving. It doesn’t matter if 35/36 cells have 10% left - the weakest cell defines the range.
  3. People often ask me “what is the range of your EV”? I say “I don’t know - and I don’t want to find out!”. Just like a petrol car it is bad news to empty the petrol tank completely. So we avoid fully discharging the pack, just like you avoid emptying your petrol tank.
  4. Range depends a lot on how you have been driving. For example lots of hard acceleration will drain your pack quickly. Power requirements increase sharply with speed. At 30 km/hr I use just 18A, and 60 km/hr 45A, at 80 km/hr 75A. This is probably due to drag increasing, it takes a lot more energy to push through the air at high speeds.
  5. Fully discharging your battery pack is bad on the lifespan. For example the Lithium cells that I am using have a 2000 cycle life at 80% Discharge, or 3000 cycles at 70%.

From driving my EV for a year I have an experimental figure of about 120Wh/km, about 50% higher than the 5 kW @ 60 km/hr cruise figure (5000/60 = 83 Wh/km). This figured was worked out from the range of my lead acid packs. So with a 11.5 kWh pack this gives an estimated range of 11.5/(0.12) = 95.8 km. Lets de-rate to 70% to be kind to the battery pack and allow for variation in traffic conditions and the “weak cell” lurking somewhere in my pack. So we arrive at a range of (0.7)(95.8) = 67 km.

Lithium versus Lead Acid Battery Racks

I decided to build a new battery rack for the rear of the car, and to modify the front rack as it also supports other items (such as the speed controller) and is more complicated and harder to rebuild.

There are a couple of cool things about Lithium compared to lead acid:

  1. Having a large number of smaller batteries makes it easier to fit into odd shaped compartments, such as those found in cars. Each of my Lithium cells is the size of a large paperback novel, 4 of them took up the same space as a 12V lead acid cell. I used this convenient fact to fit blocks of 4 cells in the front rack positions where lead acid batteries used to sit.
  2. Lithium packs take up less volume overall that lead acid, their volume/energy density is higher than lead acid. Put another way - I get my boot (trunk) back! The rear Lithium pack ended up fitting in the spare wheel bay at the bottom of my boot.
  3. Weight is the biggie. My previous lead acid packs weighed in at a hefty 280kg, the Lithium pack around 112kg. This means I can now seat 4 people rather than 2, and stay beneath the legal GVM of my car. I estimate the curb weight as around 900kg, just 40kg over the weight in Internal Combustion Engine (ICE) configuration.
  4. Lighter weight has a knock on effect on battery rack construction. The rear rack only needs to restrain 70kg of batteries instead on 180kg, each of the blocks of 4 batteries in the front weigh just 13kg rather than 32kg - lighter than a regular car battery! So lighter battery racks can be built saving more weight and safely securing the racks is easier.

Building the Lithium Battery Racks

By trial fitting Lithium cells in various parts of my car I worked out a rough idea of where they would all go. I ended up putting 21 in the back, and 15 in the front. My welding skills dictated that the design would be welded up out of 20 x 20 mm right angle mild steel. I started with a simple base that held the bottom of 3 rows of 7 cells:

The curvature in the photo is due to my camera. The right angle pieces were all 500mm. Compared to lead acid Lithium cells are harder secure. Instead of 8-10 batteries I now have 36 that must be kept from rattling around. The sides of Lithium cells should also be restrained otherwise they can bulge during heavy charge or discharge. I used plywood panels at either end of each row of batteries to restrain the ends.

To cut the metal to length I use an angle grinder with a thin cutting disk. Wear safety glasses and ear protection. My arc welder is just a low cost $200 model. Tip: don’t arc weld in shorts. I speak from experience.

I welded up a top section with right angle around the outside and 20mm flat across the top.

The whole thing gets clamped together using threaded rod at each corner:

OK so now I hit my first problem. Lithium batteries have a lot more exposed terminals than lead acid packs. The top section of my rack was just a few mm away from shorting out dozens of connections. What to do? I ended up raising the top section 20mm using wooden battens as spacers. You can see the wooden spacers in the photo below of a trial fit in the back of the car:

The wooden spacers raise the metal top section above the plane of the terminals. I painted the rack using grey pressure pack primer and black gloss paint, $3 a can from the auto shop. Quick and easy, and looks nice.

The rear rack is bolted to the car via 8 bolts through the thin sheet-metal of the spare wheel bay. On the underside of the car the bolts run through lengths of 20mm flat to spread the strain around the thin sheet metal:

The previous lead acid rack (supporting 200kg) was bolted through the chassis rails but with the low mounting location and light weight of the Lithium rack I feel comfortable with a lighter mounting method.

The guidelines we have for battery racks in Australia are hard to interpret and impossible to test. I spent a lot of time and energy worrying about battery racks on my first two EVs conversions. My conclusion is that ultimately it’s up to the subjective opinion of the inspector on the day you get the car checked out. As described in my EV bugs post I found the whole inspection experience Kafkaesque, but some people breeze through it.

In the absence of useful specifications I design battery racks by comparing the weight to people. My back rack weighs 70kg, which is about the mass of one person. A person is secured to the car at three points using a woven seat belt and 12mm bolts fitted to reinforced points on the pressed sheet-metal chassis. So I ask myself, “would this rack design hold a person in the case of an accident or roll over?”. (In the case of the lead acid racks it was three people.)

I am less concerned about the batteries in the front as I figure in an accident where are they going to go? At worst they might bounce around the engine bay, but will be unlikely to penetrate the firewall into the passenger cabin. My ICE car battery is secured by a plastic molding (!), and my Lithium cells weigh much less. I test them by shaking each rack as hard as I can and making the car bounce around.

The rear rack sits nice and low in the spare wheel bay, with the carpet replaced I have nearly a full boot for shopping. I don’t carry a spare tyre, as I reason the EV is always no more than 20km from home and a rescue mission can be mounted by our other car.

Front Racks

I used similar construction for the front rack (photo at the top of this post). I welded in extra rails to the existing racks so I could slide in linear blocks of Lithium cells. The top sections were the same as the rear rack, and the same wooden spacers were used. There is room for a few more cells should I want to upgrade.

If this was a new conversion I would have placed all of the front Lithium cells in one block, as interconnecting them with cables and threaded rod terminal posts is a pain compared to using the strap type interconnects.

First Impressions

After a few weeks of messing about in the shed I backed my Lithium-powered EV out for the first time. My first impression was that I felt like I was in a 4WD! Removing a few 100 kg of lead made it sit up about 50mm higher than before. But it felt like 2 feet at the time!

There was no big difference in acceleration, in fact the car is not as zippy as with the lead acid pack. This is surprising given the lighter weight and my previous lead acid pack was just 96V, compared to the Lithium pack which cruises at around 115-118V. Guess there is nothing like the low internal resistance of a fully charged lead acid pack. However if I put my foot down I can still get 400A out of the Lithiums off the line (around 45kW at 0 rpm) which would give many cars a good run for their money.

The current is nice and low, about 45A at 60 km/hr which is great. The car does feel lighter around corners and over bumps, but it’s not a huge difference. I have done one run of 50km on one charge (in light traffic) so far, but most of our driving is 15km round trips, and we tend to charge between trips. After 50km the voltmeter read 115V, or 3.2 V/cell. Unlike lead acid batteries, this doesn’t tell me much about the state of charge. Lithiums seem to sit at 3.2V all day long then fall over in a big hurry. I really need an amp-hour meter to know where I am at.

Charging

I have designed a BMS Controller for the Lithium pack that let me recycle my old lead acid chargers.

I measured the power to charge the EV after a couple of test drives and arrived at a figure of 170 Wh/km (measured at the wall). This seems high compared to the 120 Wh/km figure I used above but may be due to charge efficiency of the batteries and chargers. An amp-hour meter on the car would help reconcile these numbers.

EV Running Costs

At 18 cents/kWh a km costs us (0.17)(18) = 3.1 cents in “fuel”. If I used off peak electricity at 9 cents/kWh at km would cost 1.5 cents/km. We average 30 km/day or 5.1 kWh. This amount of electricity could be generated for free by a 1kW solar PV panel apart from the capital cost (around AUD$5,000 at the moment, and dropping).

A petrol version of this car that gets 14 km/litre would cost (130 cents/litre)/14 = 9.3 cents a km, plus much higher maintenance costs. There is no servicing in an electric vehicle, brakes and tyres are the only wearing parts. You do need to replace the batteries every 10 years but I imagine that will cost about $3,000 in 10 years time and far far less than accumulated ICE servicing and repair costs over the same period.

However I don’t like arguing for Electric Vehicles on the basis of cost. It’s funny how many conversations I have seem to focus around running costs. As if that’s all that matters. The main reason I like EVs is that they don’t use fossil fuels. Rather than burning irreplaceable fossil fuels just so I can rent a DVD I make the fuel right here on my roof.

Other Lithium Rack Ideas

Thanks to Peter Campbell for sharing the details of the battery racks in his Lithium powered Charade (same model as my car). As described in these AEVA Forum posts he used slotted steel which could be bolted together first for trial fitting, then welded.

Here are a few photos of Peter’s rear battery racks, thanks Peter!

I hope this post is useful to anyone thinking about an EV conversion. It’s the sort of information I would have found very useful when starting my conversion!

Links

David’s EV page.
Weight Distribution with Lead Acid and Lithium Batteries.
A BMS Controller I had fun designing for the Lithium pack

by david at December 28, 2009 00:26

December 27, 2009

Joachim, DL1GSJ

Receiver for 7059900Hz

Several obvious options here.

SDR using 4x the qrg. Here, we a got crystal from Nick, 28.188MHz, resulting in an SDR center frequency of 7.047MHz. Alternatively the canned 28.322MHz-oscillators provide a center frequency of 7.0805MHz.

SDR using half the receive frequency, phase shifting of 90 degrees done by an RC circuit. A crystal is available: 3.535MHz (from Rich). This results in an SDR center frequency of 7.070MHz.

And finally, there is a crystal available, from box73.de, having a frequency of 3.530MHz. This is too close for SDR, but allow for a subharmonic direct conversion receiver, more or less in the same way as I use it for 30m. The only drawback here, there is not 7.060MHz crystal yet, hence, no easy way for a sideband filter. However, there are crystals for 7.055MHz (Rich, box73.de) and 7.058MHz (Rich), which could serve as a notch filter, just like in Gene Marcus 30m WSPR transceiver.




by PA1GSJ (noreply@blogger.com) at December 27, 2009 12:06

Alan Yates, VK2ZAY

USBtinyISP Programmer

I put together a USB ISP programmer for use with my Win32 laptop.

December 27, 2009 11:28