I've started to put together a station for the QO-100, and since I don't have a personal blog, or a personal web page, I'll try to document my progress here. Hopefully it's OK with everyone.
The setup will be based on an Adalm Pluto.
I have couple useful LNB's at hand, that I will modify for an external 25MHz reference.
First step, I made a board that serves three functions.
1) Bias-T injection for the LNB DC
2) 740 MHz RX filter
3) Source for the 25MHz LNB reference
Just as a personal preference, I didn't choose to use GPS locked PLL. Instead, I decided to use a OCXO for the LNB 25 MHz, and another OCXO for the Pluto.
Picture of my bias-T/OCXO/filter board.
Frequency response of the 25 MHz LPF, and the resulting waveform.
(notice that in the oscilloscope FFT, the y-axis is 20dB per division, so most harmonics are about -70dBc)