Due to the earth's magnetic field there are just O and X modes and
neither obeys reciprocity except for special cases. Also the X mode
generally has more absorption loss, and further what you hear depends on
the antenna polarization and the sum of the O and X signals you receive
by different paths. It's a long story.
Of course local noise is probably still the biggie.
Bill N6MW
On 1/22/2023 8:30 AM, Stanley Zawrotny wrote:
I am quite certain that I have seen evidence of the skip not working the same
in both directions.
Stan, K4SBZ
"Real radio bounces off the sky."
On Jan 22, 2023, at 10:45 AM, K9MA <k9ma@sdellington.us> wrote:
That's true, but only part of the story. On the HF bands, receiver noise is
almost always negligible, so absolute signal strength doesn't matter much. If your
random wire isn't matched, all bets are off. Even modern radios have drastically
different S-meter calibrations: 3 or 6 dB per S-unit. You may also have various lossy
components in the received signal path. Noise levels also vary enormously, so even at
the same absolute signal strength, S/N can be very different. And then, of course,
there's QRM and competition.
73,
Scott K9MA
On 1/22/2023 12:10 AM, Barry Jacobson wrote:
Hi guys, it seems that in a contest like NAQP where presumably almost
everyone is running the same 100 W power, you should be able to hear the
other guy at the same level he hears you. Even if the other guy has a
$25,000 dollar beam, and you have a simple 10 foot random wire, the
weakness in your transmission ability will also weaken your received signal
just as much in the other direction. So if you can hear him, it guarantees
he can hear you. (Unless one or both of you has separate receive and
transmit antennas, or the receivers you are using are of very different
quality.) Does that make any sense?
Barry WA2VIU
--
Barry Jacobson
WA2VIU
bdj@alum.mit.edu
@bdj_phd
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--
Scott K9MA
k9ma@sdellington.us
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