Posts by G4SDG

    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.


    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