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Old April 24th 07, 02:52 AM posted to rec.radio.amateur.antenna
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Default Where does the far field start on a phased array?

Jerry Martes wrote:
"Jim Lux" wrote in message
...

Jerry Martes wrote:

"Dave (from the UK)"
wrote in message ...


Jerry Martes wrote:


Hi Dave

Would you consider building a scale model of this array to allow a
polar orbiting satellite to be the illuminator?

It's not really practical to do that for various reasons. The structure
is not a nice conventional antenna that can be scaled up/down size.



I get some pretty good radiation pattern plots at VHF, using Patrik
Tast's SignalPlotter program and NOAA satellites.

Jerry

That's a concept I have not heard of before. But for me to work at VHF,
I'd need to make the structure larger by a factor of 10, so it would be
several hundred metres long.


--
Dave (from the UK)


Hi Dave

You are not restricted to VHF. It is possible that there is a
polar orbiting satellite transmitting continuously on the frequency you
are interested in. NOAA satellites transmit continuously at about
half the frequency range you refer to.

Jerry


One can also use Ku-band DBS satellites as an illuminator.




Hi Jim

Is the DBS satellite polar orbiting?

Jerry

no.. Clarke orbit (e.g. for Dish Network or DirecTV)

There are some orbiting TV satellites in Molniya orbits for covering
Siberia that might be useful. They radiate in C band, and perhaps Ku?

The GOES polar orbiters radiate at 1.6 GHz, and I'm sure there's
others out there. GPS radiates at several L-band frequencies.

ISS radiates in S and Ku bands and is in LEO, as is the Shuttle when
it's up. I don't know if they would be useful as a source though,
because the antenna is directional and probably pointed at TDRSS or a
ground station.

 
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