That is a reasonable point, Stan. That is why I was suggesting that it
would be instructive to use logs where output power wasn't varied as
experimental controls. You could slice a "control" log up in multiple
ways to see how much difference the length of the slicing interval would
make. It could be that slicing into 10 minute slots instead 1 minutes
slots still produces nearly equal score outcomes when comparing odd slot
and even slots scores on a control log where power was held constant.
Your comments speak to another aspect of the 1dB measurement which is
context. As you point out, being loud during a feeding frenzy of Euros
chasing a Caribbean station during a strong opening can actually be a
disadvantage. OTOH, when the band is barely open to JA/BY/BU/VR2/JT on
160 or 80 meters, the 1dB could be the difference between getting over
the noise floor of a double mult and not. So at the end of the day, if
you ran the proposed experiment, you might find that 1dB does make a
certain percentage difference in score. The problem is that particular
measured difference is going to represent the average advantage over the
particular set of conditions presented by that particular contest with
the chosen length of the time slice interval. Under a different set of
particular conditions presented by a different contest, geographical
location, operator, solar conditions and/or slicing interval, the
measured advantage of 1dB could vary considerably.
BTW, I agree that it makes intuitive sense that every dB helps,
otherwise low power scores would not be on average significantly lower
than high power scores. However, how one extrapolates from the clear
advantage of an ~10dB increase to the advantage of a 1dB increase seems
a little unclear to me. If you assume that every 1dB increase in power
yields the same amount of score improvement no matter where you are on
continuum from attic dipole to multi-tower superstation, then the
benefit of 1dB should be equal to:
Benefit_1dB = Benefit_10dB^(1/10).
So if by comparing high power and low power scores, the average score
benefit of the 10dB advantage is found to be 40%, then the average
benefit of 1dB could be assumed to be 1.4^(1/10) = 1.03457 (i.e.
3.457%). Again, however, that calculation has the assumption baked into
it that all 1dB power increases yield the same score benefit no matter
what the size of your station.
Anyway, I've beat this deceased beast enough already, so I'll shut up.
73, Mike W4EF...
On 5/20/2022 3:56 PM, Stan Stockton wrote:
A couple years ago I reduced power from 1200w to 50 watts to thin a gigantic pileup
of Europeans on 160. Rate went way up after about five minutes. I think even without that
situation occurring you would have to increase the times for each power to 10 minutes or more
to see the impact. Every other minute won’t tell you anything in my opinion. Those
who have gone to great effort to gain another dB or so over what they had know, intuitively,
that it makes a significant difference.
Stan, K5GO/ZF9CW
Sent from my iPhone
On May 20, 2022, at 5:43 PM, Michael Tope <W4EF@dellroy.com> wrote:
If you use a differencing method that inserts and removes the 1dB transmit attenuator in a way
that is not known to the operator and that ensures the operators spends an equal amount of time at each
power level, then the impact of the 1dB "psych out" would presumably get spread equally
between the two power levels. The key is engineering the attenuator control so that the system doesn't
give off subtle clues that it has changed state (e.g. change in VSWR, change in plate or drain current,
sound of vacuum relays clicking, etc). Of course, as N5OP suggests, getting volunteers who are
representative (i.e. highly competitive individuals) who are willing to subject themselves to being at a
small power disadvantage 50% of the time, might be a challenge. 😉
73, Mike W4EF....................
On 5/19/2022 4:24 PM, David Hachadorian wrote:
Just knowing that you are wasting 21% of your output power in an unnecessary 1
dB of feed line loss will play with your head and cause you to perform
sub-optimally.
Dave Hachadorian, K6LL
Yuma, AZ
On 5/19/2022 3:01 PM, Lux, Jim wrote:
On 5/19/22 11:38 AM, Jim Brown wrote:
On 5/19/2022 6:23 AM, Lux, Jim wrote:
I'm not so sure that it's out of reach. yes, trying to implement it with gear from 1980 would be challenging.
But with more modern equipment, where the "radio" is a black box controlled by a "front
panel" or "computer" it gets easier.
The Elecraft K3 with second RX that is the same as the main RX, and which can
be synced with the main, allows diversity reception, and I've been using it
since 2008.
Diversity requires an antenna for each RX, spaced as widely as practical from
each other. It was invented in the earliest days of radio to counter the effect
of selective fading, which is the the cancellation of two or more arrivals of
the wavefront from the same TX that have followed different paths, arriving at
different times. The time differences cause the arrivals to have a variable
phase relationship with each other, combining algebraically to cancel or add,
depending on the resulting phase relationships. Diversity works best when the
antennas have the greatest spacing, so that when cancellation is occurring at
one antenna, it is less likely to do so, or even to increase, at the other.
And the diversity combining - doing it in analog is hard, but in the digital
domain it's much easier, and for the most part it can be done at audio (or post
down conversion to baseband or low IF).
As diversity has been practiced since the beginning, combination is done in the
brain of the operator, with audio from the two receivers in opposing ears.
That's how it's done in the K3. The result is a sort of spatiality to the
sound, a bit like the true stereo image produced by a spaced pair of
microphones dedicated to left and right loudspeakers.
Combining the outputs of the two receivers to a single (mono) channel is
problematic, because the phase relationships at audio have a good chance of
cancelling.
For SSB, yes - a simple summing won't work. But it's widely used in other
systems where there's some processing or where the baseband phase is reliable
- For instance, on AM or FM, the instantaneous audio phase will match, so you
coherently combine - typically modern diversity receive does some sort of
weighting on the basis of SNR - the stronger signal gets a heavier weight, and
when there's fading, it smoothly changes.
I will say that there are *bad* implementations - I had a car radio that did diversity on
FM, but the two paths were noticeably different time delay (as in milliseconds) so you
could hear an apparent "echo" as it switched from one to the other.
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