[amsat-bb] Re: A0 40 replacement (PSK31-Best of FM and Linear!)

[John Stephensen]

The FM PA can be more efficient than the linear PA. If you constrain the FM 
deviation to be very narrow you can get 6 dB greater power efficiency for FM 
given a fixed peak envelope power ("HF Radio Systems and Circuits," page 
59).

73,

John
KD6OZH

----- Original Message ----- 
From: "Robert Bruninga" <bruninga at usna.edu>
To: <amsat-bb at amsat.org>
Sent: Thursday, September 05, 2013 12:44 UTC
Subject: [amsat-bb] A0 40 replacement (PSK31-Best of FM and Linear!)


>> As long as AMSAT-NA needs to concentrate on... Cubesats...
>> I would really like to see the pursuit of linear transponders...
>> on them instead of single-channel FM repeaters.
>
> We can have the best of BOTH FM and Linear!
>
>> But we used to use a ucc1 in the navy to receive messages.
>> http://www.virhistory.com/navy/rtty-mux-ucc1.htm
>> It would allow us to receive something like 16 or 32 separate traffic
> channels on one frequency.
>
> We have that now in PSK31.  Up to 30 channels in a single audio channel.
> So the ideal AMSAT transponder is a linear receiver (on 28.120 MHz) and an
> FM downlink of that single channel on UHF.  This has the advantage of 30
> individual linear uplinks to share amongst everyone, and the advantage of
> FM downlink so that everyone gets the same waterfall without added
> Doppler.
>
> It's a win/win.  And it is FULL duplex so that everyone can transmit
> simultaneously and everyone can receive everyone simultaneously.  What
> more fun can that be!!!
>
> See the design: http://aprs.org/psk31uplink2.html
>
> And it all fits on a single 3.4" circuit board. Easy to fit in any
> Cubesat.  Two such flight ready boards are ready by the Brno University in
> the CZECH Republic.
>
> Bob, WB4APR
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