Can something also be said for take-off angles?
Using a higher antenna, the transmission from station A might arrive at station
B in one hop. If station B has a much lower antenna, the transmission from B to
A might arrive in two hops. I believe each hop loses 10 to 20 dB. If both
stations use the same transmitting power, I believe A will be stronger at B
than B will be at A.
73, Rich, N6KT
On Wednesday, January 25, 2023 at 12:16:39 PM PST, Bill N6MW
<billsstuffn6mw@comcast.net> wrote:
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
>>> _______________________________________________
>>> CQ-Contest mailing list
>>> CQ-Contest@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/cq-contest
>>
>> --
>> Scott K9MA
>>
>> k9ma@sdellington.us
>> _______________________________________________
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