Posts by G8JGO

Quote from HB9SKA

Hello David

The "why" behind full-duplex operation is an often asked question, also from our short wave friends QRV now on QO-100 (I'm more than 30 years QRV on OSCAR's). I found a good article about this theme:

https://www.onallbands.com/ful…key-to-satellite-success/

I wish you success and 73

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Thanks very much for the link. Interesting reading, but doesn't really answer the question IMHO. I understand full duplex is needed to listen for relay confirmation in an orbiting sat and to correct for doppler. But with QO100 being a stable platform as such I'm still curious about this from a geostationary point of view. If I'm being asked to follow rules, I'm always curious to know why the rules are there

It seems, to me, that the requirement for mandatory full duplex is more than just monitoring your own transmission - which is a good practice of course - which does not seem to work anyway as there are some poor quality signals on the satellite!

I do intend to be full duplex anyway once I get TX working, and my interest is in measuring the full path audio response from transmitter to receiver. I've also got a little project underway to build a 2.4GHz CW/FSK (AM) transmitter from a DDS/PLL. I put AM in brackets as it would be easy to modulate the PA to allow for some voice - I know, I know... I think that is the subject for another post

Thanks 73.

Quote from DB2OS

--> Full-Duplex operation is mandatory

Sorry to sidetrack this interesting thread a bit. I don't, yet, operate TX on QO100 but I can't find the reasoning behind the "why" for full duplex. Is it simply to monitor for LELA? (Or why max 2.7KHz either when there seems to be a lot of unused space on the satellite - of course I understand if it's busy and operating close to others). Interested from an experimentation point of view.

Back to the thread. In broadcasting there is a technique called "mix minus". I have an audio mixer has a telco channel so that a person who telephones into the station cannot hear their own voice back - they only hear the presenter (live or talkback for cueing) and, optionally, the station output. So If I understand correctly this is the same technique but using DSP cancellation and delay compensation that is being tried out here - interesting.

Many thanks, David.