Tuesday, 15 November 2016

Testing U3S now on 30m

Another LPF finished and installed on my Ultimate 3S beacon. This one is in the position 5 slot, so maintaining the increasing frequency order (40m in slot 0 on the main board, 30m in 5, 20m in 4, and so far 10m in slot 1)

So far its been received nicely across Western and Northern Europe, and into the central region, but also across the pond into Florida. Not bad for a touch under 23dBm into the antenna system, and that not perfectly matched.

The only gripe I have is that there is no clear space on the componant side of the LPFs to mark which band they are tuned for. I have written the band on the underside of the PCBs, but thats not visible when they are plugged in. I might mention this to Hans on the group, but I dont know how he could adjust the design to provide a write space, as the boards are very compact. Perhaps a few mm extra board on one end and a white silkscreen?

Saturday, 12 November 2016

Ultimate 3S Relay kit

The relay board kit and extra LPFs for my U3S beacon arrived yesterday, so I found some time to work on them today.

As with all Hans' kits, its very compact but goes together very easily, excellent quality. I did find the nylon pillars were a bit awkward to fit due to being so close to other components, something that would not be a problem if the stand-off for the display was screwed into it, rather than the other way around. I removed my pins connecting the RF out, then realised I could leave them, and tried to put them back but couldnt clean the holes out properly and ended up making a mess of it! So they were left out permanently. Not to worry though, im unlikely to revert to single band operation.

The above shows the relay board fitted onto the U3S. This is revision 5 of the board, which includes a novel modification to increase the harmonic suppression performance, but it does require the highest frequency LPF (in my case 10m) to be left permanently installed in position 1. Position 0, that is, the LPF location on-board the U3S, I have left my other original filter for 40m installed. This leaves me four positions for my four new filters - 30m, 20m, 17m and 15m.

I have so far only completed building the 20m LPF, and so this is installed in position 4, leaving positions 5 (30m), 3 (17m) and 2 (15m). The only other thing to do is make sure that the correct 'band', that is, the relay position number, is set in the software so that  the corresponding filter is selected to match the operating frequency. I have already modified my two transmission settings for 40m and 10m to match the new filter arrangement.

I have also recently been trying to program some old Philips PRP70 series radios, but so far without success, despite having a genuine programming lead. I suspect theres a corrupt file in the software, as it throws up a run time error that seems to relate to file handling in MS-DOS. I have three of these radios and only really need to get one working, as that will go on 4m.

More bits ordered from the Far East are beginning to trickle in. Several cheap multimeters, just to give me some extra metering capabilities, but one of the little analogue meters ive had to have refunded, as it is totally dead! I suspect i'll be able to fix it so long as its not the coil in the movement itself.

Ive also received the 24v 3A SMPSU block, which, as feared, is slightly wider than the 1Ah clansman battery case i'd hoped to fit it into! I need to test it anyway first, but I think I will have to look out for a 4Ah metal cased battery to decell and turn into a mains supply instead. I could perhaps switch the casing on the LiPo pack.

Tuesday, 1 November 2016

Ultimate 3S WSPR Beacon Success

After some further testing, I moved the U3S into the shack today ready to go on air. Some advice from Hans Summers regarding the GPS module allowed me to get that working, and after a number of false starts due to settings, it went on air on 28MHz around lunch time.

Not a single spot!

10m conditions clearly not up to much today! Powered from a 12v 7Ah SLAB, via a modified 3v/5v regulator board (el cheapo, intended for Arduino and R-Pi prototypes), the U3S was working away quite happily, so I changed the frequency, swapped the LPF, retuned the DX-70, which was acting as monitor receiver, and moved to 40m...

And was spotted a dozen times on the first transmission!

Ive been running on 40m since then, at 10min intervals, heres the spots for the last 6h -

Not bad for a mere 200mW! Rather than try and explain what the U3S does when its running, ive done a little bit of a video of it. This shows it from just before transmission, when during the gap it displays the GPS data, to just after the start of a WSPR transmission


Immediately after transmission, the beacon calibrates itself using the GPS 1PPS signal, before putting the synthesiser into 'Park', that is, running but on a frequency safely away from the operating band, to keep it warm and so avoid drift,

I will try 10m again tomorrow.

Clansman PRC-349 on 6m?

The PRC-349 is generally shunned by the amateur community, being as it is the bog-brush haired back-stairs sprog of the Clansman range. Its quarter of a watt output power is mediocre at best, and its 150Hz tone squelch system makes it awkward to interwork with non-Clansman radios. But perhaps its biggest drawback is that it doesnt cover any amateur bands.

Shame really,

But should this be the end? Why cant it be converted? This is something ive been looking into.

There are a number of problems that would need to be overcome in order to move the 349 to somewhere it might be useful -

- Its coverage 37 to 46.975MHz
- Its tone squelch system
- Its 25kHz steps

Lets look at each of these in turn,

Coverage - ok, so its a good way from anywhere, but, the move to 6m (50MHz) from 46MHz isnt too far, and the front end might just adjust, if not, it shouldnt be too hard to retune.

Tone Squelch - The squelch system needs to see a 150Hz tone at >3mV at the discriminator output. Hmmm, shouldnt be too hard to inject a suitable tone here

25kHz steps - ok, so this is harder. But - we would also need to pretty much replace the Tx and Rx VCOs and the synthesiser anyway to convert the set, so the new control system would just be built for 10kHz steps as required.

Heres my thoughts - Replace the synthesiser and the VCOs with an Arduino Nano, and a DDS module. Most DDS modules have multiple outputs so one for Rx and one for Tx. The original switches could be reused, or other suitable types fitted to get easily selectable steps. The Arduino takes care of all that. The Tx mic audio would need to be modulated onto the Tx side of the DDS, I believe this is not too hard to do. Some waveform shaping I think might be needed though. The Arduino can generate the tone to defeat the squelch.

Perhaps a trial on the bench might be in order...