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Re: re:Linear Trasnponders



Hi AMSATs,

>On Sun, 20 Apr 2003, William Leijenaar wrote:
>
> > >With many universities building satellites, My guess is that if someone
> > >would build a small 30 KHz wide linear transponder, that someone wouild
> > >find a ride for it.
> >
> > Only a 30kHz SSB reciever makes not a transponder. And why only 30kHz..
>
>My observation of Amateur Satellites over the last 20 years has never seen
>even 30 KHz of transponders in use.  Thus why build 100 KHz wide
>transponders and just waste power.  30 KHz could support 9 separate voice
>QSO's and either 10 CW QSO's or 30 PSK-31 qsos.  I have never heard of
>anything approaching that on FO-20, FO-29, RS12-13, AO-40 or any other
>bird.  Except maybe one day a year at Fielday..

Maybe not 30kHz when you add all stations together, but that is just why 
some wider band (50kHz or more) is good. With more frequency space, many 
modulations and tests can be done at the same time. Then don't forget the 
doppler effect. Many qso's slightly drift in frequency because of doppler 
corrections by hand.
With some more space between qso's its no problem anymore.

Then about the wast of power, thats not true. When there are 3 stations on a 
bandpass of 30kHz or 150kHz, the power is the same !! The little extra 
transmitted noice is not that bad.

> > ... and why PSK31 ?...  A transponder has the best advantage that you
> > can do many modes and > experiments, not only PSK31...
>
>Our PSK-31 linear transponder on PCSAT2 is only 3 KHz wide.  I would much
>rather let 20 people use the bird at once then just have the same old
>"too-crowded" problems that we see on the FM birds... where only one user
>at a time can fit.

In your first lines you supposed to build a 30kHz wide transponder for PSK31 
use, so I don't understand the 3kHz now :-{ Maybe you mean a one channel 
PSK31 reciever ?

>
>Bob
>
>

73 de PE1RAH, William


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