[CQ-Contest] Reciprocity in signal strength

Stanley Zawrotny k4sbz.stan at gmail.com
Sun Jan 22 11:30:36 EST 2023


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
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> 
> 
> -- 
> Scott  K9MA
> 
> k9ma at sdellington.us
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