On 5/18/22 11:02 AM, Jim Brown wrote:
On 5/18/2022 10:33 AM, Lee Hiers wrote:
K1DG has a presentation he's done for Contest University. Per his study
over time, he estimates that a 1dB improvement in your station
results in a
6% score increase in a contest.
N6ZFO, who worked as a statistician in big pharma before retiring, did
a statistical analysis of Sweepstakes scores comparing high power to
low power (1,500 to 100W), and came up with a comparable number.
My own observations were from 160M contests, when I was S&P up and
down the band without retuning my amp. The difference in power output
varied by 1 - 1.5 dB. I would call stations I'd miss on a second pass,
and failing to work them, retune to get back to full power and work them.
Yes, as Jim Lux says, could be prop, but this happened often enough
for me to believe it was probably power.
Copyability of a signal is largely signal to noise ratio. In my
professional life in pro audio, I did voice paging in office buildings
in the presence of background noise (largely HVAC systems, but also
office noises). When balancing those systems, a change of 1-2 dB often
made the desired difference.
I suspect that it's SINR - interference is a big deal (e.g. breaking a
pileup at the Rx end, which you may not be aware of at the Tx side) -
and a 1 dB change could turn you from -0.5 dB under the interferer to
0.5 dB over the interferer, and that makes a big difference in "Pdetect"
- even if you ignore ionospheric fading. 0.5 dB is 12% louder
The Cocktail Party Effect (or selective attention) is what is operating
here. And it's well established that a "familiar voice" is worth quite
a bit (or, I suspect, one's fist, if operating CW). Another key aspect
is "trigger words" or specific phraseology - there's a reason why ATC
talks with pilots using a standardized form, and, of course, classic CQ
calls or contest exchanges are a similar thing. From a straight level
standpoint one can look at what's called the "Masking Threshold" - I'm
sure someone has done it for speech, but most of what I see is for
tones. And your ear is *really* good at separating closely spaced tones,
some plots on Wikipedia (from Ehmer) seem to show that a few Hz is
sufficient to reduce the masking level to 0dB for tones at 500 Hz.
We're also really good at separating spatial sources, so binaural
listening fed from two different antennas might also be very good.
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