Posts by DH2VA

    Hm.. let's do some math. The offset is around 10cm to fit next to the LNB and the lever arm (focal length) of a f/D=0.7 is 80*0.7=56cm. So the angular offset is arctan(10/56)= 10 deg.

    According to G3RUH (60cm dish) a 60cm dish has a -3dB beamwidth of 16 deg, so 8deg offset is -3dB. The 80cm dish should be more focused and we are 10 deg off, so I would at least expect -5dB or ca. 1/3.

    So your quoted 8-10W fits nicely with the 2-3W I was hoping for with a perfect setup.

    How much power do you run? I tried something similar with 20W and was less than impressed by the resulting signal on the transponder. The squint angle between LNB and helix is probably too large at my side.

    Assuming the direction to the satellite is correct, 5W and 22dBi should work nicely. So either you don't have 5W or the antenna is not 22dBi.

    great catch Clive! Although I probably have the tools to solder this here, I fully admit I went for the 'expensive' 20 USD solution.. but probably after factoring in connectors, case and time it's not so expensive anymore. Good to have both options!

    It kind of fits in this forum section and as I made good experience, I would like to share it.

    got it from Ebay and works like advertised. Cleaned up my mixer signal from LO leakage.

    some words here on the TQP7M9103. I got my driver board today, which claimed 16dB Gain and 29dBm P1dB. From the datasheet, it was obvious that this cannot be given over the full frequency range as the Qorvo device needs a bit of matching at the input and output.

    First measurements: 6dB gain and ca. 20 dBm P1dB. I suspect therefore that this could be improved with some snowflaking (Faehnchenschieben) and as this is low enough power to be safe, I'll go for it :)



    The output inductance (L1) for the bias supply also seemed a bit large to me (too low SRF) so I exchanged it to a part with known parameters (22nH, 0603, 4.6GHz SRF) but this improved matters only little. Will try some snowflaking over the weekend.

    G4NRT 15m of LBC400 would be something like 3.5dB transmission losses incl. suitable connectors. So 20W from the transverter will be around 9W which is plenty for a 1m dish for SSB. For downlink, use any good quality 75 ohm sat cable (good screening). 15m at 750 MHz IF is of little concern for the high gain LNBs used.

    OK, 'Coverage peak'. We are in Europe also in the Coverage peak. Thats I meant. You say these are "worst case numbers". How many dB or Watt would you add ?

    Europe is not in the coverage peak. The coverage peak is at the nadir direction of the spacecraft, which is actually in the Democratic Republic of the Congo (90 deg elevation). With elevation of 33 deg for central Europe we are closer to the EOC (edge of coverage), hence the "75cm elsewhere" recommendation.

    om0aao you are in the right ballpark and you can use the cited document as further guideline. There is only so much we can say due to NDA's but not only do you need the satellite RX antenna gain but also its noise temperature. That is why G/T is quoted in the above table.

    And then of course are there some more confidential numbers for the downlink part..