Radio and rails...

Yes, ok, this is still not about the transmission path! But I wanted to experiment a little more with the wideband part of the transponder and DATV signals. To that aim I press ganged the small HD screen from our NVR (which in turn will be wired to the large TV downstairs) and attached it the the Winterhill box. With 12V from the lab supply to the Winterhill and the 25MHz LO being fed from the diminutive Leo Bodnar mini GPS reference clock it all appears to be working as expected. This was covered in Part 2 already but today I managed to get a screenshot with four DATV feeds, although one had just dropped leaving the last image that was received. Now I need to decide whether to keep this small screen for Winterhill or swap screens with the one I use for Hamclock with the latter then on the smaller screen. I will probably do the latter as this small screen will run from USB C from the PC meaning one less socket.

Some days ago the diminutive DX Patrol GPSDO (v3, multiple outputs) would quite often lose PPS and coordinates. At first I thought it was the GPS signal as it is still only using one of those little puck type antennas stuck to the window. On recommendation I placed this on a metal sheet but the problem persisted. Also, checking the antenna against other GPSDOs showed it worked fine. I plugged the USB into a PC to see if there was any errors and for the duration of that the device functioned perfectly with no dropouts. This was with both the 12V supply and the 5V from the USB powering the device. Long story short it transpires that when the GPSDO is running from the 12V shack supply it keeps dropping out. The supply is fine. When just powerd from USB it works fine. So that's the way it has been left now. It has the advantage that I can see the data output but the annoyance that the USB socket is on the front - however, a down bend USB adapter plus a down bend cable neatly brings the USB lead back under the GPSDO. As I understand it a…

This part was going to be about the full transmission path but I am still getting the POTY and LDF4-50A line ready. Instead, I wanted to experiment with the SG Labs 13cm transverter. For the test the FT818 was dusted off and set to 432MHz FM so it would give a constant output when keyes. This fed the transverter, the output of which was put into a dummy load via a 20dB directional coupler that in turn fed a frequency counter. The output was giving 2,404MHz and was nicely stable over a couple of hours (not keyed all the time of course). When finished the transverter will be locked to a 10MHz reference from a GPSDO. The output power was around 18mW, again via the directional coupler, so about 1.8W. The FT818 was not set to full power and the PA, when finally installed has a maximum input of 250mW so some attenuation is still needed. Ok, so I have a full receive path for both transponders, I can decode FT8, hear SSB and see DATV. And I am now happy that I will be able to transmit once the PA and POTY are all in place. My next thoughts…

The reason I moved the dish was, as explained in part 1 partyl due to me wanting to send and receive DATV. Having sorted out the receive parts for the narrowband transponder the next step was to set up to receive the wideband one. the LNB was originally a 4-port device which has been modified to take an external 25MHz sinewave input on one of the ports thus leaving three free. I ran three runs of RG59 from the shack, one for the 25MHz feed and two for reception. So it was relatively easy to use the second of these to receive DATV. I already had a Winterhill DATV receiver (see https://wiki.batc.org.uk/WinterHill_Receiver_Project ) and documentation for this shows how to configure it for QO100 use using two of its inputs, leaving the other two free for other purposes. A splitter combines the two 'top' ports, feeding power from the first port. With the Winterhill set up to send 18V it flips that LNB receiver to the right polarisation for the wideband transponder. QED. And it just works. I did have to fiddle with settings because when I got the Winterhill I experimented with remote access so when turned on it…

Finally I had a chance to set up the QO100 dish on the side of the house. It was originally behind the harage at ground level which was not ideal as it was both a head-hitting hazard and an RF hazard, especially as I eventually want to be able to send not only SSB but also DATV which requires a higher power output than the 4W I had originally. I also wanted to copy the special GB2RS broadcast on QO100 which was scheduled for the 28th September, 2025. So, out with the scaffolding and up with the dish. That was the easy part. The disk elevation was already set so all I needed to do was point it in the right direction azimuth-wise. I nearly got that right using a theodolite app on the phone so with the aid of all relevant hardware I tuned it to max, for now anyway. It was rather amusing to have to set up a laptop and power supplies on the scaffolding as the last time I did that was at ground level. Cables came next - three runs of RG59, each around 12 metres back to the shack. These were very fiddly but…