[amsat-bb] Re: Full Duplex?

John M. Belstner jbelstner at yahoo.com
Wed Jul 27 10:25:38 PDT 2011

Hi Mike,

Others have answered the question quite well.  One additional point I'd like to 
make is how important it is to actually listen to your yourself on the downlink, 
for a couple reasons.

1. On an FM bird, if you can't hear yourself or you hear a double... Stop 
2. On a linear transponder (CW, SSB), use only enough uplink transmit power to 
be heard on the downlink.

For #2, the rule of thumb is to compare your downlink signal strength to that of 
the satellite's beacon and adjust your uplink power so your downlink does not 
exceed that.  A satellite PA can only put out so much power (say 1W).  So if 
your uplink is 20 dB stronger at the satellite than anyone else's, your downlink 
could be transmitted at .99W leaving only 10mW for the rest of the QSO's in the 


John Belstner W9EN
Valley Center, CA  DM13le

----- Original Message ----
> From: Mike <mikef1234 at buckeye-express.com>
> To: amsat-bb at amsat.org
> Sent: Wed, July 27, 2011 5:25:49 AM
> Subject: [amsat-bb]  Full Duplex?
> I'm having a difficult time of understanding the concept of Full Duplex.  Can
> anyone explain it to me? I have the ARRL satellite book, read about it  in
> there and Wikipedia. I still didn't understand how it works with  a
> transceiver setup like we use.
>         Mike   N8GBU
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