Prep for geostationary tests

I’ve had no time to make proper progress on the deep space project recently. However the launch of Es’hail 2 in November made me think about another step along the way. I have a steerable dish (even though it’s not yet computer controlled), so I can steer it towards geostationary satellites easily!

The Es’hail beacon and transponders will allow for some useful tests; and Brian GM8BJF gave an interesting talk at the Lothians club recently showing how it could be done. So the first step is to make a bias tee for a LNB:

Bias tee for LNB

I found a useful screened box on the IF section of an old microwave unit, and have made a very simple bias tee to squirt 12V up to the LNB.

The signal is shifted from input to output via 100pF and 1nF capacitors in parallel; the 12V is decoupled to ground with 100pF, 1nF and 10nF capacitors. The bias is fed through an inductor which is (I think) about 8μH. Here’s the other side:

Bias tee – input from LNB to the BNC, output from the SMA

More soon – initial tests look OK.