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 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.
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.
I finally mounted the dish. It’s been cluttering up the workshop for months now. My original plan was to mount it on a pole by the workshop which would have needed a concrete base and regular trimming of the apple tree and hedge. So, it’s mounted on the garage wall with a TK bracket.
Aligning it wasn’t too bad except I managed first to find the Astra satellite at 19.2 degrees thinking it was the one at 28.2. After I found the second one it was not too difficult to find a satellite carrying Qatar TV using the GTMedia V8. With bolts tightened a bit and after rigging all the gubbins up I found the beacon via an SDRPlay SDR and SDRUno but the levels were well down. The Pluto and SDR Console did a far better job so there will be some setting I overlooked. I copied a couple of QSOs but working outside on a Sunday with the whole estate doing gardening made it rather hard, even with headphones! Anyway, the Pluto is the one that will be used so good to see the whole RX chain working. I have some decent WF100 cable for the LNB feed but will need to make something up for the GPSDO feed.
Next step is to mount the Pluto, bias tee and PSUs inside the garage and use Ethernet back to the shack. There is a convenient air brick next to the ironmongery.
The POTY is back inside for now and I’ll need to make a rain cover too, but it feels like progress finally.
This was awkward. I found some info on the Web where someone had used a USB to Ethernet adapter and a Y-splitter cable to connect their Pluto to their LAN. So I got the exact same bits off eBay. Nope, no go. I resorted to asking on the very helpful Facebook group and tried all the advice, for example powering it via the separate USB power socket, but still no go. So, a process of elimination – the USB adapter worked fine on the Mac so no issues there, nor with the CAT5 cabling in use. But I did not have a separate mini-USB to USB socket cable, only the splitter cable. Back to eBay…
A cable arrived today and the Pluto appears on the LAN just fine. So it’s the Y-splitter cable that is at fault. Not tested it yet but it’s only a couple of quid so no biggie. Serves me right for not keeping things simple and using a splitter.
Anyway, one step closer to my QO100 project! All I need now is a decent way to get Ethernet out to the workshop. I do need a LAN out there anyway, not just the house wifi, so either a cable or a wireless bridge.
Been having fun with the Pluto today. It has been working fine, though not used very often with SDR Console on my acquire Windows 10 laptop but today I needed an SSB source to find a fault on the TR-9130 which had gone deaf on SSB. The Pluto made an ideal source and helped me to find out I’d got the gain and RIT controls mixed up and so had turned the gain right down! D’oh. So, after putting the TR back on the shelf it gave me the opportunity to finally fiddle with the Pluto.
First off, when transmitting on SDR Console the transmission breaks at a regular short interval. Googling (well, actually these days DuckDuckGo’ing – does that work?) found some info which I tried but to no avail. Someone mentioned that it worked fine in SDR Angel so I downloaded this and after watching YouTube I managed to get a decent output. Not sure what I’ve done wrong with SDR Console but that will wait for now.
But I really wanted to use the Pluto on the Linux box. Some time ago I had a go at installing the Gnu Radio software along with the modules that make the Pluto work. Ages back I tried but I could never get it to compile but since then I have upgraded Ubuntu to 18.04. This time it all seemed to go in but the software cannot see the Pluto. There is something obvious that I am missing here.
Anyway, I installed SDR Angel on the Linux box via snapd and it loads fine but it cannot see the Pluto. Probably no surprise because Gnu Radio can’t either and I had forgotten of course!
As an intermediate step here I have ordered a USB to Ethernet adapter as someone posted information about this and he can access his Pluto that way. That doesn’t mean I will carry on trying to crack why the Pluto is invisible to Gnu Radio and SDR Angel but it will help once I finally get the dish set up for QO100 as the Pluto will be out in the workshop as close to the dish as possible while still under cover, and I will want to drive it over the wires. More on that later as I still need a decent galvanised pole and some concrete and we’re still locked down here.
For completeness on the Pluto issues, iio_info -s finds the Pluto fine, and avahi-resolve —name pluto.local tells me it is on 192.168.2.1 as expected. But neither iio_info -n pluto.local or iio_info -n 192.168.2.1 will work, both stating ‘Unable to create IIO context: Connection timed out’.
Update: Typical. Reading what I have written got me thinking that this is simply a routing issue. When plugged in the Pluto appears as a USB Ethernet device and fails because it is not on the same subnet. Closing that and running ifconfig by hand I updated the Ethernet device Pluto ‘becomes’ by giving it the IP address 192.168.2.2 and the netmask 255.255.255.0 and now I can see the Pluto – I can ping it and iio_info -n 192.168.2.1 finds it. and running gnuradio-conpanion (NB I already compiled this with the relevant libraries for the Pluto) it can see the device.
My current issue with receiving QO100 (not got round to transmitting yet, baby steps!) is where to put the 1.2m dish. I don’t really want it on the wall or at the front of the house as it’s grey and huge. It can’t go at the front of the workshop due to an apple tree and if it goes anywhere on the garden we’ll fall over it. I’m currently thinking that the bit of land we have at the back of the garage will do and I can easily run the cables into the workshop from there, or even put all the RF side of things in the garage. But with no cable route from the garage to the shack (aka the little bedroom) it seems I will need the SDR co-mounted with the RF bits and run it via Ethernet or Wifi. Of course, there is also the wall outside the little bedroom but then we’d see it every time we gaze over at the moors…
Update 11/April/20 I’ve worked it out. There is room at the front of the workshop to the side of the apple tree where the dish will see the sky if it’s up maybe 4 foot. The mount I have is 3 foot so my ‘plan A’ is to get a 4 foot 2″ pole and an extender clamp, set some concrete (whenever we’re out of lockdown) and get the dish up. This makes it a doddle to feed the cables into the workshop.
Finally I had time and reasonable weather to have a go at receiving QO100 today. I know I can receive the satellite because I’ve used my GT Media V8 and managed to resolve the TV channels. No home for the dish yet so it lives in the workshop between fiddles.
Anyway, today was a bit of a comedy of errors but did result in success. First off, dish out, LNB in and aligned to the satellite. All good. I replaced the LNB with the POTY and got absolutely nothing on the V8. So I remembered I need the external 25MHz source so grabbed my Leo Bodnar GPSDO and the Windows laptop to make sure it was set up. Success, I can see the TV again.
Next was to set up the bias tee, PSU and cabling, the SDRPlay RSP2 and the SDR on the PC. After a bit of fiddling I did manage to see traces but I have yet to investigate the SDR software on Windows so it was off back indoors for the MacBook. Note to self: remember to learn how to use software before you need to actually use it!
The MacBook and CubicSDR proved the setup. I managed to decode a couple of SSB transmissions and decode the morse on the band edge beacon: “HI DE QO100 QRA DK0SB”.
Anyway, here is the lash-up. The signals were quite weak and clearly I need to do some adjustments yet but that really needs to wait until I fix the dish somewhere.