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Re: Re: Let's build some Linear Transponders



On Mon, 30 Jun 2003, Pieter Ibelings wrote:

> What is the Input voltage that makes the most sense for a small LEO?

The smallest practical so you can use larger and fewer solar cells per
side.  The total number of cells on a side has to add up to your buss
voltage no matter wht it is.  The fewer cells, the less wasted space in
interconnects.  In a 4" satellite, this is critical.

These days with all the cell phone and laptop pwoersupplies it is not
inconceivable to use a set-up DC-DC converter either, but the efficiency
is critical...

Bob
 > > Pieter >
>
> >From: Bob Bruninga <bruninga@usna.edu>
> >To: William Leijenaar <pe1rah@hotmail.com>
> >CC: amsat-bb@AMSAT.Org
> >Subject: Re: [amsat-bb] Re: Let's build some Linear Transponders Date: Mon,
> >30 Jun 2003 12:23:55 -0400 (EDT)
> >
> >On Mon, 30 Jun 2003, William Leijenaar wrote:
> >
> > > Then I still don't know why amateurs still want one mode satellites,
> > > like a PSK31 transponder.... What is the purpose of it ??? What kind of
> > > improvement it will give to amateurs world ???
> >
> >To provide a multi-user linear transponder that can be powered by only a
> >4" solar panel (Thats all you get on a cubesat).  Such a transponder can
> >support up to 20 or more users in a single 3 KHz passband.  The
> >improvements are:
> >
> >1) Not FM, no capture effect
> >2) Multi-user "broadband" transpnoder (3 KHz)
> >3) Will fit and be powered by a 4" cubesat.
> >
> > > Transponders are ideal to do tests with, like sstv, ssb, psk, and even
> > > psk31... with many stations at the same time... That most amateurs only
> >want
> > > to talk or do just this one mode they like I know, but keep in mind that
> > > there are also amateurs who like to do tests... :-)
> >
> >Yes, but if you do SSB, or SSTV in the 3 KHz transponder then it is a
> >single USER satellite again that so many have pointed out is a
> >problem...Yes it can support them, and yes we may experiment with special
> >passes, but my experience is that it is better to have a satellite comm
> >system be in one mode ALWAYS so that users know what to expect instead of
> >being dissapointed in changing operations..
> >
> >Of course CW is very narrow and would be allowed  in  a small portion of
> >the passband.  But we will ddetermine that once we are on orbit...
> >
> >Bob
> >
> >
> >----
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de WB4APR@amsat.org, Bob

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