Well, that made quite a difference! I removed the POTY from the QO100 dish today and replaced it with a ‘Bullseye 10kHz’ LNB sourced from Amazon and advertised as a ‘QO-100 Bullseye TCXO LNB’. It’s just clamped in place with no attention to position or skew. Winterhill plugged in and instantly I see pictures.
The LNB behind the POTY only managed negative values in the MER and D fields, this one seems too work rather well. No idea what happened to the old LNB but these things happen I guess. It’s dry and had a waterproof housing. I’ve used the existing CT125 cable and connectors. Now to put the Winterhill box in a better location than just sitting on a ladder tied on with a bit of wire!!
The above photo shows the Winterhill viewer and console on the left and the Quick Tune on the right, all working nicely.
As I said before I want to use an actual transceiver for QO100 work rather than the Pluto. A precursor to that is a 2400MHz transmit capability and so I now have a nice new (used, new to me) SG Labs 13cm transverter, complete with the PCB log periodic antenna. It is already set up for the correct frequency range and seems fine… so, the next step is move the dish, clear the loft in that area, and get the kit up there. The transverter claims to put out 2W so I can use the existing AMSAT UK PA via an attenuator (max input is 200mW) which should get me 4 to 5W to the dish and has been adequate in the past when using the Pluto. I will first try with just the ‘raw’ 2W and see if I can get into the satellite. The eventual aim is to use an 80W PA I have ready so I can use DATV as well as SSB or digimodes – that also takes 200mW input – but as yet I don’t have a suitable PSU.
Well this got off to a bad start! Ahead of my plan to move the QO100 disk so I can get the electronics in the loft rather than the garage I wanted to test out the Winterhill box to see if I could pick up any DATV on the wideband transponder.
The Winterhill box generates the 18V necessary for the LNB so in theory it was just a matter of pulling the coax feed from the bias-tee in the garage and putting that into the Winterhill. That done, I could see the occasional signal but never a picture.
Now, I had noticed that the NB beacon strength had dropped a while ago so today I decided to adjust the dish in case it had been knocked. That snowballed! I needed a laptop so I could see the signal strength while at the dish (remember the dish is on the garage wall currently at about 6 foot, so easy reach). Of my two laptops one is a Mac and had no SDR software, the other a Samsung Netbook running Ubuntu and terribly slow. I tried setting up several SDR packages on the Netbook and failed miserably. At this stage I need to state that after a lifetime working in IT and solving problems I now have no time or patience to solve my own, so if something fails it goes to the bin!
So, the Mac. CubicSDR refused to even think about installing. I found SdrDX which works with the USB Funcube dongle amongst other, mainly networked things. This worked just fine.
Mac out on a lab stool in the shade, SdrDX and the Funcube running, the bias-tee in the garage powered up, a cable fed out the garage back to the dish and into the Funcube… fortunately it didn’t all fall over and actually worked. So I adjusted the dish but only gained a couple of dBm more than before no matter what I tried. Oh well…
Back inside and plug the Winterhill in. Back upstairs to the Windows PC and now I see locked signals but just not enough signal strength for a picture.
I wonder if the LNB is full of spiders…
Anyway, now the QO100 kit in the garage is in bits I can’t transmit so it can all stay as it is. My next plan is to remove the POTY and install an LNB and see if that gets me any DATV pictures, otherwise I am a bit stuck. The 1.2M offset dish has a clear view of the sky and should be ideal – it worked just fine for SSB on the NB transponder. I never got round to sorting out a GPSDO input for the Pluto but I am about to get a SG Labs 3cm transverter and plan to use an actual transceiver for tx once the dish is moved.
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.
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.