Posts by G4SDG

Thanks for confirming Peter. It was operator error here, or I prefer to think it was my PC changing settings itself!

73 Chris

Has the telemetry changed recently? Initially using AO40rcv I could decode the page with the message from Bochum and then later from Qatar but now the programme is not locking up at all. Last night I also thought I could hear some intermodulation on the beacon from a strong SSB station.

73 Chris

My 25 turn helix was based on this design (eg http://www.amsat.org/articles/g3ruh/117.html) and uses a square aluminium tube. I should have explained that the 5 turn feed is for single band only, in fact a reworking of my AO40 feed as the original helix had fallen of while “in storage” and I couldn't find suitably thick wire to make a new one. Originally the 15mm tube had been just to the rear to support the reflector and ended flush with it but in the reworked version I used a longer pipe to additionally support the helix. The pipe is not acting as a 10GHz feed.

I suspect that the 5mm tube used for the helix might present too much blockage for a dual band feed and I'm making a patch feed instead with the 22mm feed for 10GHz and a dielectric window from a Rocket LNB.

Thanks for the calculations. Once done I'll make some proper measurements of feeds and the 25 turn helix all using the same power level.

I've used 5mm (3/16" actually) outer diameter copper brake pipe for a 25 turn helix antenna and also a 5 turn feed for my 90 cm off-set dish. I had my first Es'hail 2 contact with the 25 turn helix but had to use a Spectrian amplifier too at about 30W. With the 90 cm dish I can run an SG Labs transverter on its own (probably only 1W) into about 9m of 3/8" Cellflex with about 2dB loss and get a reasonable signal off the satellite. The transverter SWR indicator is green but I've not got around to actually measuring the match.

Quote from pe1chl

The beacons are RHCP. So not suitable to set the skew angle of your LNB.

Thanks for confirming that.

I've been using a Funcube Pro dongle and SDR-Sharp which seems to limit my visible bandwidth to ~+/-75KHz but when I checked with an analyser I can see sidebands on both beacons at ~+/-250KHz but only the additional sidebands at +/-15KHz on the 11205.5MHz beacon at the moment.

73 Chris G4SDG

Hello all,

I am a bit confused about the polarisation of the two beacons. I set my 1.4m prime focus antenna up a week or so ago and couldn't get a decent polarisation adjustment on the 10706MHz beacon so I used one of the TV muxes instead to achieve an approximate setting. For the last week I've been seeing the 10706MHz beacon with a S/N of about 38dB and the 11200.5MHz beacon with S/N of about 18dB so I assumed I had some cross-pol still. Today however I'm seeing 11200.5MHz with S/N of 38dB the same as the 10706MHz beacon, although today the higher one has modulation at +/-15KHz and the lower one does not. So, are they linear or circular, or is it just a case of spacecraft manoeuvring or power level changes?

73 Chris G4SDG