Still works fine… poor little dish all out in the cold of winter…
It’s snowing fairly heavily here today and I wondered what effect, if any this would have on my QO100 reception. Very little it seems. There is no loss of signal strength when viewing the lower beacon, but the noise floor has raised a little.
There’s not a great deal on the dish but then it’s pretty much vertical. There is a wedge of snow at the bottom of the POTY rain cover.
Clearing the snow off made no noticeable difference to the signal. It’s snowing less now and still nothing noticeable. I need to compare with a clear sky… which we had the next morning. There is actually very little difference, the noise floor appears better but it’s very hard to say by how much and indeed if this is even real. The signal strength appears very slightly better. Without proper measuring methods it seems the snow and ice made hardly any difference.
A combination of things finally came together. I’ve never played with digital SSTV before, plus I had some time to fiddle about and wanted to see if I could decode some of the digital stuff from QO100. Finally, I received a couple of nice digital pictures of the Dakar rally from F6HA, neatly incorporating my previous main love of motorsport! My setup is far from perfect (read, a series of accidentally cobbled together bits): Windows 10 laptop running the excellent SDR Console and connected to my QO100 transceiver via Ethernet, audio mixer feeding from the laptop and to the Linux PC, and QSSTV on the Linux PC. There is a lot of noise in my QO100 setup that I need to figure out because it really messes up analogue SSTV and seems to have made these digital modes even more fiddly. This is probably not helped by the audio running round the shack. In an ideal world I’d have a decent Windows PC with two screens and a virtual cable. That needs to wait until we sort out what is to happen with an older PC desktop here as if it is to be replaced I will nab it and repurpose it as the shack PC, dual-booting Windows and Linux.
Next step will be to try and transmit, though I will start with analogue SSTV. And this will definitely wait until I get a Windows desktop because running transmit audio around the desk will make a further mess. KISS rules here.
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…
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.
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).
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.
(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.
So, I’ve been running the Pluto over Ethernet to SDR Console on an old but still capable laptop just to see how it performs end to end. It clearly has issues! The first test was just pinging the Pluto from my Linux box with no SDR activity. This ran for almost 7 hours and dropped out in the early hours.
Then I tested it with SDR Console running to see if it would last as long. 10 minutes! Another similar test lasted about 1h45. I added ferrites to all the power leads and this time it lasted about 3h30. Nothing at all scientific in these tests and I had already read up on Ethernet issues and the need to strap ground connections together internally but wanted to just see if the ferrites made any difference.
Back to the workshop and I strapped the earth end of R58 to the earth end of D3 following the instructions found in this YouTube video at 7m36. The video describes that as the ‘simplified version’ – I’ve seen another more comprehensive one but this one is straightforward. There is a detailed investigation of the issue here and here. The Pluto held up running SDR Console looking at the lower beacon for 30 hours and is still running as I type this. I’ve not gone mad like running an electric drill next to the Pluto but so far, so good.
Edit: SRD Console has been running for 47 hours now with no issues. I only stopped it because I need to sort out the PSUs and coax entry for the QO100 transceiver box in the garage.
After ages I finally made a rain cover for the POTY and led cables into the garage. Big delay there because the garage was a tip. It still is a tip, but the mess has been rearranged so I have access to the air brick where the cables come in!
It’s nice that when they built the house in the 1930’s they put an air brick right there knowing it would be needed for a satellite dish…
The rain cover is made from a sheet of plastic that came out of a smashed LCD monitor. I bent it round a bit of 110mm drain pipe using a hot air gun. it didn’t quite come out as intended but it’s near enough. The front is from the same piece of plastic and is epoxy glued on – yes there is a gap where the glue was less gluey, I’ll fix that later. Nylon threaded bar and nuts hold it in place. And it rained an hour after I made it so it does actually work.
After all the messing about everything still works. There is a nice box on order to take the gubbins – ok, the Pluto, bias tee, Leo Bodnar GPSDO, power supplies, oh yes and the pre-amp and amp I have yet to build. I’ve got Ethernet into the garage and I have tested SDR Console over Ethernet to the Pluto and all seems to work ok.