[amsat-bb] Re: Technical discussions on AMSAT-BB......"an endangered species" ?

[Bob Bruninga]

> I'm curious, as someone who was involved in designing 
> a nanosatellite.  What sort of payloads would be of 
> interest to the amateur community?

The A#1 Killer AP is something we have tried twice on short li=ved missions
and which we already have ready for our next mission, (but no launch
opportunities) is a PSK-31 transponder.!  It is really more than you first
think:  Please see:

http://aprs.org/psk31uplink.html

1) Normal HF PSK-31 uplinks on 10 meters where the Doppler is 14 times less
than on the typical UHF downlink.

2) VHF or UHF *FM* downlink.  Notice FM.  This means what EVERYONE see's on
their waterfall is EXACTLY whateveryone else sees.  Thus, everyone just
jumps into the 3 KHz FM audio bandwidth wherever they see an empty spot and
then can even see THEMSELVES full duplex because they are transmitting
linear PSK-31 on the uplink on 28.120 while simultaneously seeing what
everyone else is seeing on the VHF or UHF FM downlink.

3) Because you see what every one else sees, including yourself, you can SEE
your good signal or your bad signal, AND you see how you are shifiting in
Doppler and can correct for it.

4) AND because it is full duplex, you TX the entire pass in a steady stream
while looking for QSOs in the downlink.  We could have 20 to 30
SIMULTANEOUSE QSO's going on at the same time and even be talking to all at
the same time.  

It is the ULTIMATE satellite transponder, because:

1) Full duplex
2) Minimal Doppler
3) You correct for your own Doppler
4) 20 to 30 simultaneous users
5) Free software, no hardware!
6) Vertical 10m antennas are IDEAL power-levelers.  When overhead (and 10 dB
closer) the signal arrives at the satellite 6 to 10 dB down due to the
vertical antenna pattern.

It's a win-win-win mission.  Our attempt failed on PCSAT2 due to a broken
antenna (pre-launch integrators and astronaut handling) and our attempt on
RAFT failed due to not enough time available for the tests due to mission
conflicts during a shor 5 month mission.

Please someone do this.  It is TRIVIAL to do.  Just combhine a 28.120 PSK-31
receiver and a VHF or UHF FM transmitter.  Done.

Bob, Wb4APR

On Mon, Oct 17, 2011 at 8:55 AM, i8cvs <domenico.i8cvs at tin.it> wrote:
> Hi All,
>
> I do remember that when OSCAR-10, OSCAR-13 and AO40 were
> alive and well this net on AMSAT-BB was full of technical messages
> from W3IWI now K3IO ,G3RUH, G3WDG, ZL1AOX and many others
> from wich it was possible to lern the radio technique particularly in the
> field of RF and antennas.
>
> By the way actually with the prolification of Microsats,Nanosats and so on
> the above people seems to be not anymore interested on satellite technical
> discussions and they abandoned the net.
>
> Can anyone explain to me why ?
>
> Thanks for any answere.
>
> 73" de
>
> i8CVS Domenico
> _______________________________________________
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--

Chintalagiri Shashank
Indian Institute of Technology, Kanpur

http://blog.chintal.in
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