My Adventures in Satellite Communications - Part 2

For Part 1 see

2.4GHz Uplink Antenna

2.4GHz antenna
2.4GHz Antenna With Homemade Bracket

The antenna is now temporarily fixed to a plastic drainpipe on the side of the house using a purpose-made bracket, that provides the appropriate azimuth and elevation. The cheap ‘RG58’ cable has been replaced with five metres of high spec coax (Messi & Paoloni Hyperflex 5 Crystal). This has a specified loss of 0.42 dB per metre at 2.4GHz - not bad for a nominal 5mm coax.

CW Tone Generator

As mentioned in my previous post, SDR-Console has no built-in provision for Morse keying. Therefore I have built an 800Hz keyed sinewave oscillator which modulates the SSB transmitter, thus producing a CW signal. This is covered in detail in the next post.

My First Satellite Radio Contact

On 11th August at 1918z I made my first radio contact through the satellite! I put out a CQ call on 2400.072 MHz and got a reply and short QSO with Remco (callsign PA3FYM) in the Netherlands.

My experimental setup is shown below. I used a twin-paddle Morse key with an electronic keyer, driving the 800Hz audio oscillator. The output from the audio oscillator was connected into the microphone input on my laptop PC, which was running the SDR Console software. The rest of the hardware was as discussed in Part 1 of this article.

I do not yet have a receiving dish, so I received the downlink via the WebSDR at Goonhilly.

Experimental uplink for QO-100
Experimental 2.4GHz CW Uplink


My signal into the satellite transponder is not too strong, so I could do with more transmit power and/or a better antenna. The -12PPM frequency error inherent in my ADALM PLUTO SDR radio can be calibrated-out in the SDR Console software. However, the frequency drift (as the radio warms-up) is more problematic. One way of reducing this is to leave the SDR Console in transmit mode for a while (but without any modulation) until the frequency stabilizes somewhat.

The station should not be left unattended when in transmit mode, and the transmitter must always be switched off prior to making any adjustments to the antenna system!

Continued in My Adventures in Satellite Communication Part 3

Web Resources

QO-100 WebSDR -
SDR-Console -

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