[CQ-Contest] Reciprocity in signal strength
K9MA
k9ma at sdellington.us
Sat Jan 28 10:41:59 EST 2023
I just had a chance to measure my noise level during a widespread power
outage. On 20 meters, it's 5 to 19 dB lower than normal, depending on
direction. So, if you're in a really quiet location to my west, you're
going to need 19 dB more power to get above my noise level that I do to
get above yours. Either that, of 19 db of non-recriprocal propagation.
Unless I can track down that big noise source.
(I'm in the middle of the city, surrounded by overhead power lines.)
73,
Scott
On 1/26/2023 1:40 PM, Gerry Hull wrote:
> Interesting discussion.
>
> As many have said, the local conditions, qrm, qrn, etc play a lot into
> the equation.
> From the arctic, it is usually pretty quiet, so I can hear a lot more than
> I can work.
> Also, if there is any aurora, it makes conditions one way -- I hear
> perfectly but cannot get out.
>
> In NAQP CW, I was on from VY1AAA on all bands, with 100w. The only antenna
> that worked at all was the full-size 1/4-wave 40m vertical.
> It has the most signal "capture". Of course, that meant the most
> productive bands were 40 and 15, but even with a tuner 10 was great due
> to conditions.
>
> With a small station, it is really important to know when you can call in a
> pile and work someone. I passed by many because I knew I would
> sit there and call forever. However, that is not universally true: some
> ops are just awesome. One call for 8P5A even though he was 339 to me.
>
> 73,
>
> Gerry VY1AAA (W1VE)
>
>
> On Sun, Jan 22, 2023 at 7:52 AM Barry Jacobson<bdj at alum.mit.edu> 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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