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Re: re:Linear Trasnponders



On Mon, 21 Apr 2003, William Leijenaar wrote:

> >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...

> ... about the waste 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.

Yes, you are right.  I should not have said "waste of power" but "waste
of spectrum".  It makes satellite freqeunecy planning difficult when
each linear transponder proposes to use half of all avaliable satellite
bandwidth, yet at any one time, less than 30 KHz is needed.  Such
reservations in the frequency tables make it impossible to find
frequencies for other narrowband satellites.

And if other satellites do operate in overlaping bandwidths, then those
unintentional signals just waste transponder power.

Bob


>
> > > ... 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
> >
> >
>
>
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de WB4APR@amsat.org, Bob

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