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Re: [HCDX] HF radio signal propagation topics...
There was a paper in the IEEE about HF reciprocity in the mid 1980's which showed that HF reciprocity did not always exist. See:
"A new wideband HF technique for MHz-Bandwidth spread-spectrum radio communications"
by B. Perry, Communications Magazine, IEEE
Volume 21, Issue 6, Sep 1983 Page(s): 28 - 36
A sinusoidal signal at constant amplitude (power), swept in frequency over a one MHz HF bandwidth, was transmitted from place A to B. Then B sent the same signal back to place A with roughly identical equipment. Both received signals were recorded (A's signal at B, B's signal at A). The two signal strengths did not always match with respect to frequency. A plot of the frequency response at A did not always look like the frequency response at B. The time difference between A transmitting and B transmitting was one second (i.e. A transmits to B for one second, B transmits to A for the next second, thus alternating seconds).
Hope this helps.
Paul
Dan Ferguson <shortwave@xxxxxxxxxxxx> wrote: Tom,
IIRC (perhaps not a given anymore, if ever), signal power reciprocity is
essentially built in to the underlying prediction engine (VOACAP) upon which
the software you've used is based.
DanF
----- Original Message -----
From: "Tomas Hood (NW7US)"
Sent: Monday, June 04, 2007 10:54 PM
Subject: HF radio signal propagation topics...
> Hello, fellow SWL'er and potential Amateur Radio Operator:
>
> I'm letting this list know about some additions to my website (
> http://hfradio.org/ ). These new pages contain information that many
> radio operators will find useful (based on the feedback I have gotten
> from this material when the original was published in CQ Magazine and
> Popular Communications Magazine).
>
> One would think that ionospheric radio propagation would be
> reciprocal. That is, the signal strength in one direction should be
> the same as in the reverse, or reciprocal, direction. In HF ray-trace
> theory, the distance is the same and the ionospheric control
> points-the points where the wave is reflected (or more properly,
> refracted) back to the ground-should be the same. This is an
> interesting topic for those using very low power, for example. Can
> your signal be heard well at the distant station, and can it compete
> with other signals that might be originated with a higher energy
> level?
>
> I explored this (is HF propagation reciprocal?) in a recent CQ
> Magazine "Propagation" column. I've posted the meat of the text at:
>
> http://hfradio.org/ace-hf/ace-hf-reciprocal.html
>
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THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed
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