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From: Sylvia Else on 21 Dec 2009 19:37
Dr J R Stockton wrote:
> In sci.space.history message <56f2a4c0-729b-4516-bef9-850a4b0a8dc4(a)j19g2
> 000yqk.googlegroups.com>, Sun, 20 Dec 2009 10:20:49, Geoffrey A. Landis
> <geoffrey.landis(a)gmail.com> posted:
>
>> This is worth emphasizing: you can't use phased array techniques
>> ("synthetic aperture") to make multiple small transmitters widely
>> separated look like one big transmitter-- this works for receivers,
>> but not for transmitters.
>
> That appears to conflict with the well-established principle that, in
> linear systems (no valves or semiconductors) electrical energy goes
> equally well in either direction.

It's not transmitting electrical energy.

Sylvia.
From: Peter Fairbrother on 22 Dec 2009 00:34
Geoffrey A. Landis wrote:
> On Dec 19, 1:01 pm, Pat Flannery <flan...(a)daktel.com> wrote:
>> ...
>> Sylvia's multiple SPS constellation with the individual satellites
>> widely spaced certainly has simplicity on its side.
>
> I'm coming in late to this discussion, but it's worth pointing out
> that the reason that solar-power satellite concepts are large is that
> you need a large transmitting array to make a small spot on the
> ground. (the canonical numbers are that a 1 kilometer transmitter in
> GEO puts a 11 kilometer spot on the ground, assuming 2.45 GHz). This
> drives the sytem to large sizes.
>
> Unfortunately, if you put up multiple satellites with small apertures,
> the ground footprint you get is based on the size of the *small*
> apertures, not the total area, and not the effective size of the
> phased array. This is the "Thinned Array Curse"-- I wrote an article
> for Wikipedia on it once http://en.wikipedia.org/wiki/Thinned-array_curse

I have that on my to-read list, but could a phased array antenna in
space put out two beams at once? [yes, but..]

And perhaps more importantly and relevantly, could a ground antenna
accept beams from two space antennas?

-- Peter Fairbrother

(pissed as several farts, eleven judges, and a newt!)
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