An example: My QO-100 setup
Main goal was to achieve a transceive operation with a 70 cm TX/RX, my already existing FT857D. I wanted to avoid tuning in procedures, and the digital mode equipment setup with my FT857D should be usable for FT8 and other modes too.
The SG Lab. transverter is stabilized with a GPSDO at 10 MHz and the modified LNB is fed with a 2nd GPSDO at 25.7884615384615 MHz to get a transceive setup: -> 10,489.550 MHz - (25.7884615384615 x 390) MHz = 432.050 MHz
TX: 432.050 - 432.300 MHz to 2,400.050 - 2,400.300 MHz
RX: 10,489.550 - 10,489.800 to 432.050 - 432.300 MHz
The modified Megasat Diavolo Twin LNB sits behind the 55 cm offset dish in a waterproven box. I cut the waveguide and mounted a short semi-rigid cable with a SMA plug, to feed the RF input directly via a suitable 1 pF microwave SMD capacitor. There are in total 40 cm of 3.6 mm semi-rigid cable and 60 cm of 10 mm Hyperflex cable between the BAMATECH dualband feed (DJ7GP) and the LNB. Compared to a LNB directly at the focus of the antenna (without the dualband feed) I loose 3 dB of SNR. So this is the compromise I accept for this architecture.
The CW beacon generate S7 at the FT857D and the SDRplay (running SDRuno) shows -105 dBm with a noise level at -135 dBm (7.5 Hz resolution bandwidth). The difference to the WebSDR is very small. Only the very weak signals which you hardly could recognize at the WebSDR too, are difficuilt to copy.
The transverter and PA from SG Lab. are in an outdoor cabinet (Outdoor Box 1). Some relais and attenuators are built in to switch between high and low power. Considering the attenuation of the cable between the outdoor box 1 and the feed, delivers 200 mW (for digital modes) or 10 W to the feed. 10 W generates a signal similar to the BPSK beacon level.
On the RX path a variable attenuator brings the noise level to S0 at the FT857D. The SDRplay is fed via a splitter and another variable attenuator. This is for the visual reception. Of course, the SDR can only be used to a limited extent in transmit mode because of the crosstalk directly into the SDR on 70 cm. For monitoring my own signal I use one of the WebSDRs.
Power supplies for 24 V (PA), 12 V (transverter and LNB) and 5 V (GPSDO) are within the outdoor box 1.
Just to get an idea regarding the effort. The overall expenses were about 900 Euro, not considering the already existing FT857D and some parts like relais, plugs, cables and so on. It took me 3 months to set this up.
CU on QO-100,
73 de Matt, DF6LO