Fiddling with APRS

I’ve been fiddling recently with trying to receive satellites but without all the going outside and waving yagi antennas around… I’ve heard a few QSOs on DIWATA 2 and there is a very good pass in a day or so where I may be able to get a call in. This is using the Trio TR-9130 as receiver as it has a horizontal dipole connected, and the FTM100DE as transmitter, though so far without success on transmit.

Anyway, I remembered the FTM100 has APRS built in and the ISS often sends and receives this in 145.825 and so I’ve been leaving the radio switched on. Today I noticed it did indeed receive packets from the ISS.

I also downloaded UISS by ON6MU which seems to ‘just work’ – nice that, I downloaded it and ran it and it found the sound card and returned an APRS message on a later ISS pass. Oddly, the FTM100D did not decode that message (the squelch is set to 0). It comes with a module called SoundModem by UZ7HO which seems pretty comprehensive. Another package to play with…

Boxing day

A minor project requires a metal enclosure so I got one off eBay. I have a 5V PSU and three Pi’s to install to keep these all nice and tidy. The enclosure is sized to take the PSU and has ample room for the Pi’s and a fan.

The enclosure arrived and is surprisingly well made for the price. It has plastic surrounds front and back. The front and rear panels are held with screws and the top comes off. There are two metal runners inside to maintain the structure with the top removed. Not a bad little case.

The only odd thing is the description. Apparently the features of the case are ‘surface mounted’, ok I expect this means ‘sat on a desk’, and ‘underground electrical enclosure switch junction box’. Not so sure on that one!

QO100 dish alignment experiments

After some fiddling I now have a decent amount of signal coming down from QO100, but also questions. The azimuth was already correct and I had adjusted that to maximum signal strength on a TV channel with a GT Media V8 Finder. But the elevation is numerically wrong, or the markings on the dish are wrong, which is more likely. Fiddling with elevation got the strongest beacon signal at about 26db and 26 degrees marked, but the AMSAT info says it should be around 23 degrees at my QTH. Mind you, for all I know the garage wall is not perfectly vertical! All SSB signals look good now except for one or two that are difficult to hear.

However, having got that far, no adjustment to the position of the POTY in the arm or its skew make any noticeable difference, so I’ve left that one.

Also, when transmitting a tone from SDR Console it actually peaks higher than the beacon so I had to reduce the drive appropriately. An SSB signal test showed very poor audio and no adjustments in SDR Console got it to where it needed to be. Turning the mic gain up in Windows itself cured that and gives me a decent looking envelope when viewing the returned signal in SDR Console.

I just need to force myself to take it all to bits again and sort out the GPSDO input to the Pluto…

ATVo6″

Since I built the Minitiouner I’ve had nothing to test it with except a quick test on the Astra satellite to prove it actually worked. Not any more. I now have a Portsdown ATV transmitter setup thanks to a recent advert for one for sale (saved me having to get all the bits). No PA, no antennas or anything else here yet, but I did at least manage to send a test card from it to the Minitiouner over 23cm and at the grand distance of 6 inches.

It all needs a nice case yet but it’s a good start. This might even persuade me to bung my 23cm yagi on the chimney and see if I can actually receive GB3YT – it’s not too far away but there is a house in the way.

Exams

Scary stuff. The RSGB announced (yesterday I think) that the full licence exam will be available to be booked online from today. I’ve booked for mid-november to give me time to actually learn this stuff… (yeah, I know… probably not that bad though because I have an electronics background so it’s more a matter of making sure I don’t miss anything daft).

QO100 success

Got myself a Heil headset for the laptop as the built-in mic picked up room noise. So, I figured it was time to try a QSO on QO100 even with the floating (frequency wise) Pluto. And – success! I had a short QSO with a German station.

Just waiting for some small signal diodes to arrive before I glue the GPSDO output to the Pluto. There is a modification that involves removing the 40MHz TCXO and connecting an external source but the Leo Bodnar GPSDO output is 3.3V, too much for the chip in the Pluto. The mod involves two diodes in antiparallel to earth, plus a capacitor between the Pluto chip and the diodes, and another between the diodes and GPSDO. Hopefully that will work and the surgery on the Pluto does not consign it to the scrap pile! The GPSDO I have has two outputs, one 25MHz to the LNB, and one 40MHz for the Pluto.

I still need to sort the dish as signal strengths are still below where I expected. I am also concerned at the filter/pre-amp because it does not draw as much current as it is supposed to – it works but I wonder if there is enough drive. It may be perfectly ok but the next step has to be locking the Pluto so it doesn’t wander all over the place.

Someone having issues on QO100

Caught sight of this today. At first I thought it was my kit but the QO100 WebSDR showed the same. It started before 10:29 UTC (the first photo, below was taken at 10:29) to 11:37 UTC (it went on after that and I did not record the end).

10:29 UTC, sounded a bit like a fast data transmission.
10:30 UTC, a short burst of the same followed by a much wider band transmission.
10:31 UTC and something tuning up perhaps? The signal strength plot (no screenshot) looked like a strong carrier and lots of harmonics, kind of like you see when keying a handled near an SDR.
This one definitely sounded like a data transmission. I can’t remember the mode but lots of tones and quite ‘musical’.

QO100 sort-of success

Overcast today so I made time to try to align the dish a little better. One long Ethernet cable got the laptop under the dish and with SDR Console looking at the beacon I did manage to peak it a bit but I think I can do better yet. Oddly, no amount of moving the POTY in or out or skewing it made any noticeable difference. I did note however that the rain cover I made only makes a tiny bit of difference. The sky is a little overcast today so maybe signals are down because of the cloud cover.

Anyway, I made a test CQ call and could hear my voice coming via the WebSDR nicely, so I made a couple of CQ calls but got no reply. I think I chased everyone away because after this there was very little activity. So, at least I know I am getting out and so a success at least in part.

One thing though, the tuning is going to take some getting used to yet. The basic frequency conversion between the 10GHz band, the 2.4GHz transmit and 739MHz receive is 10GHz – 9750 = 739MHz rx frequency, and 10GHz – 8089.5 = 2.4GHz tx frequency. With my setup the receive frequency needed for SDR Console to get the same audio tone as found via the WebSDR is 6.8kHz higher but the transmit frequency is 21.8kHz higher. These offsets are repeatable in that if I chose a signal on the WebSDR I can reliably find it via the Pluto if I use the offset.

So, maybe a bit more dish alignment but also I do still need to sort out the frequency lock for the Pluto.

One small step…

(updated) I finally had all the bits in one place to sort out the power supplies for my QO100 box. I managed to assemble the ‘filtered S-band driver/amp’ and the ‘QO100 5W amp’ kits from AMSAT UK and learned a lot about SMDs like (a) I don’t like them (!) and (b) I find it far easier, being short sighted to just look up close than use magnifiers. Anyway, the kits both went together as planned and passed the basic test relating to current draw so I was hopeful that I had actually not managed to mess them up. I also had much fun assembling the LMR600 coax with memories of central heating installation!

Finally, with a 12V PSU, a 12V to 5V module and as 12V to 24V module from eBay and tie wraps to hold stuff in place I managed to get volts where needed and gingerly turned it all on. The Pluto found the Ethernet, the GPSDO lit up and SDR Console found QO100. Nothing odd in that because it was all working before but is now assembled into a box.

On the left (the door) are the two voltage converters and the GPSDO, and on the right the Pluto (LHS), the bias tee (central) and the 2.4Ghz amp (RHS) with the driver/amp above. The most awkward bit is the USB to Ethernet adapter. The LNB input, 25MHz output and the GPSDO input cables enter from underneath and go out to the dish via the white conduit, and the LMR600 enters through the side into a short piece of LMR195. There is a 12V PSU mounted on the outside of the door in a separate box.

But does the transmit side work? That’s all new. With a Windows laptop running SDR Console and the MacBook looking at the WebSDR both sitting on the freezer in the garage (so I could see if the QO100 box caught fire!!) I managed two very short test transmissions. It works! The audio was a bit naff but that is probably down to me not yet familiarising myself with SDR Console and using the mic in the laptop.

So, after ages and ages of getting bits together and everything else getting in the way it’s almost done. Signals are still down compared to other, more successful setups out there but at least now it seems all I need do is properly align the dish and sort the audio side out. And tidy the wiring. Oh yes, and sort out the GPSDO locking for the Pluto.

4m FT8, a first for me

Had my first 70MHz FT8 QSO today, and I think the third anything on 4m because there’s little activity here on FM and I only just got the transverter. There was a surprising spot at -23db and 1,443km to Poland but then an actual QSO with a Welsh station at 126km. So the converted ‘FM radio’ dipole in the loft works, as does the transverter.