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.

HOWEVER, if you're looking for gnat's eyelash precision, watch out for
atmospheric irregularities/inhomogeneity dominating the measurement.
When you start to get to many km as your "distance to adequately
replicate plane wavefront" the propagation uncertainty will probably be
the greatest source of error. You get "bubbles" of air with local
variations on the scale of meters.

A more practical approach (depending on the precision required) is some
form of near field measurement (or a measurement where the different
path lengths from the radiator to the observation point are explicitly
taken into account).