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dxAce · January 18th 07, 05:15 PM posted to rec.radio.shortwave

bpnjensen wrote:

wrote:
dxAce wrote:

But, is it 'sucking it out' or merely propagating it somewhere else other than
that particular spot where your antenna is?

And that 'somewhere else' might not be very far away, but merely a few
wavelengths in distance.

dxAce
Michigan
USA

Before satellites carried most of the milcom they used "diversity
receivers".
Two, or more, receivers tuned to the same frequency but located some
distance apart.
The logic being that when the singal faded at one location, the other
didn't fade at the
same time. The more important a comm cicuit the more receivers spread
over a wider
area.

A friend and I played with our receivers feeding phone patches and
since we live 30
miles apart it was clear this approach was workable. With signals that
experienced
deep fades we were able to listen to nearly all of the time. Real
(commercial or
military) had AGC based voting systems to decided which signal to pass.
We ran
into issues of our audio phases shifting producing very odd sounding
"flanging"
effects.

I have often thought about trying this with receivers whose antennas
are only a few
hundred to thosand feet apart. I never have gotten around to it.

The military also used freqeuncy diversity, sending the same singal on
more then one
frequency. Kind of like listening to WWV on 5 10 and 15MHz at the same
time.

Terry

Fascinating. It sounds like a couple of antennae, maybe even on the
same property but spaced some modest distance apart, maybe a few
hundred feet, and phased into the same radio, might also be a solution
to the problem.

Anyone try this with a 50-acre lot and a phasing harness?

I don't think that would work properly. In practice, I think you need the 'voting
machine' that works on two receivers AGC to pick the best signal.

I do recall some folks trying to emulate this to a certain degree by having two
receivers, two antennas widely seperated (more than a wavelength), and feeding the
audio to headphones (one receiver in the right ear, one in the left).

dxAce
Michigan
USA