[CQ-Contest] Reciprocity in signal strength

[Bill N6MW]

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 at 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 at alum.mit.edu
>>> @bdj_phd
>>> _______________________________________________
>>> CQ-Contest mailing list
>>> CQ-Contest at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/cq-contest
>>
>> -- 
>> Scott  K9MA
>>
>> k9ma at sdellington.us
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