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RE: commutating antennas (was snip)



At 10:04 PM 5/4/2002, Steve wrote:
>So would this then require an increase in the size of the bird to make up
>for the area taken by the antennas? As near as I can figure, if there are
>only four bands used; 2m, 430 MHz, 1.2 GHz and 2.4 GHz; then it would
>require one antenna on each face for each band. Therefore, on a bird with
>six sides we would be looking at 24 antennas. How much would the power
>budget be impacted with this much shadow area from this many antennas?

I don't propose that we build satellites that transmit on many bands.  In a 
satellite with a reasonable number of bands, you will have a reasonable 
number of antennas, and this isn't a problem.  I don't see why a particular 
satellite needs to transmit on more than one band.

How much area is taken up by the antennas also depends on the size of the 
orbit.  At GEO you need big antennas, but at moderate altitudes, the 
antennas can be small.

You talk about power lost, but you forgot to talk about the big signal 
power gain due to having the antenna(s) pointed toward earth all the 
time.  That's a big win.  The satellite needs less power as a result.

I think its a signal power win, not a loss.

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