Re: Can cell phones and SPS share the same frequency?

In article <[EMAIL PROTECTED]>,
TangoMan  <[EMAIL PROTECTED]> wrote:
>How powerful is 900 W/m^2 compared to other radio frequency users in other
>bands? Military radar, TV, radio, etc.

The fast answer is, a whole bunch. :-)

900 watts is a hefty transmitter for non-broadcast communication uses --
that's 900 watts *total*, spread over thousands of square kilometers even
if it's at a frequency that is strictly line-of-sight, giving power levels
at the receivers down in the nanowatts per square meter at best. 

Big broadcast transmitters can be up around a megawatt, if memory serves,
but they're also covering substantially larger areas (which is why they
want very tall antennas).  People living near those can have problems with
more distant stations on nearby frequencies being drowned out, especially
on cheap receivers.

I think big fixed radars can also be up in that range of power output, and
there things are a bit more complicated because of relatively narrow
beams.  Right in front of the antenna, they may be comparable.  At any
distance, much less. 

Powersats are really in a category by themselves. 

>Do you have any idea on much leakage there would be from the SPS beam and
>how far from the beam that leakage would impact other users?

I know this *has* been looked at in some depth, but I'm not familiar with
the details.  Rough guess:  effects would be most conspicuous in an area
around the rectenna, probably many kilometers wide, but there would be
lesser leakage covering whole regions. 

>What prompted my question was the realization that the beam would be in a
>discreet zone aimed to each rectenna. If every rectenna was rated at 5 or 10
>GW, then rectenna wouldn't be a dime a dozen and perhaps there could be an
>exclusion zone for the frequency just around the rectenna sites.

I think the beam frequency itself is just going to have to be reserved for
powersat use and nothing else, on at least a continental scale.  The main
question is impact on nearby frequencies, and the worst forms of that are
likely to be more localized.
-- 
MOST launched 30 June; first light, 29 July; 5arcsec    | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well.  | [EMAIL PROTECTED]