My test worked, so I'll try again...
To everyone that has commented: Thank you very much! This discussion is
fabulous!
I concede the point that statistically, there is likely to be score
improvements with 1 dB power increase and certainly 2 dB. These are best
described as statistical improvements and I suspect that the data set
has to be moderately large to detect a "significant" difference, that is
for a statistic to have much power. Thus a DXer, who is not a contester
(there are such things) probably won't notice a significant improvement
in how long it takes to break through a pile-up with a power increase of
1 dB. Over a long run, a contester will be able to see a score increase
at with a 1 dB power increase. A smaller data set (possibly much
smaller) will show statistical score improvements given a 2 dB increase,
significant at some arbitrary p-value.
I tend to skepticism when someone says they can notice a significant
improvement given a *single* contest assuming everything else (including
the operator) is held constant. It will take several contests to see a
*statistical* improvement but I'll now bet it's there. Fewer contests
will be required for a 2 dB increase. I prefer resampling (i.e. a
permutation test) to parametric statistics simply because parametric
test assumptions are almost always violated, leading to unknown
degradations of the test's validity.
Dave's response is precisely what I would expect to see. I became aware
of diversity reception early in my ham radio experiences and that it
could lead to huge effective signal increases (10 - 20 dB) but it's not
trivial for a typical ham installation. I heard about it as it related
to multiplexed encrypted RTTY military applications.
I've always assumed that propagation was king: without favorable
propagation, we're sunk. I re-read the section on fading in Ken Davies's
book "Ionospheric Radio" (I knew him when I worked in Boulder and he
gave me an autographed copy) about the mechanisms of fading -- I don't
recall Jim Lux's notes about ionospheric "lumpiness," but it makes
*perfect* sense, and it's right there in black and white in Davies's
book as well. .
A personal historical note: when my dad (W5JHJ) worked in as an
engineering physicist, he developed an instrument to fly on the KH-8
surveillance satellites that would help us determine the vehicle's
orientation. The KH-8 orbited pretty low (80-200 mi) and so was in the
ionosphere. Of course, I was only a kid (elementary school) at the time,
what he did was Classified, and he only told me the whole story when he
was long-since retired and the program was mostly declassified. His
instrument used the acronym "AIM" (I never knew what that acronym stood
for) and was later called a VVSA -- velocity vector sensor assembly. It
measured ion current through two perpendicular ports and, based on the
difference of the currents, determined the direction of the "wind." At
the time, it was a challenge to know exactly how it was oriented, so the
idea was to sense the ionospheric "wind." The AIM did that quite well
but they found strange anomalies indicating that in places the
ionosphere had very high velocity winds, on the order of the orbital
speed of the KH-8, which rendered the AIM useless for its intended
purpose. They had f made unintentional direct measurements of
ionospheric winds; this was all sometime in the 1960s. These currents
were hypothesized by Kristian Birkeland and then detected by him based
on magnetic anomalies, all in the early 20th century. Of course, none of
what my dad was part of was ever published because it was all
classified. By the time that veil had lifted, we had radar measurements
of the these currents and so what my dad was inadvertently part of
finding was never written up for any publication.
Kim N5OP
On 5/18/2022 7:53 PM, Dave Sublette wrote:
I've hesitated to chime in here because I thought the problem was being
discussed very well and perhaps I don't have anything to add. But I do.
>From December 1983 to April 1989 I operated 160 through 6 meters from
Kwajalein, Marshall Islands. The pileups were big and were there every
time I pressed a key or opened a mic. I made 83,000 QSOs, filled 19
logbooks. There were no home computers for me at that time.
One night things were a bit slow on the bands and I had three stations in
San Diego on 20 meters to keep me company. All were running comparable
stations. KW and tribanders at 70 feet. They all lived within a couple of
miles of each other. So I proposed an experiment. I had them each say a
sentence in turn, perhaps no more than 6 seconds. And keep it going
around, one sentence after another. I watched my S-meter. At any
given moment, one of them would be 10 to 20 dB stronger than the other
two. And it was a different station each time. We did this for maybe ten
minutes and the results were as I have described.
I learned some things from this that I wish I had known while chasing DX
from the States before I went to Kwaj. Primarily, propagation is king. No
amount of power will guarantee your signal to be highest at all times. I
came to think of propagation as a searchlight, constantly scanning.
Whichever station is shined on at the moment would be the one that got
through the pileup. Had I realized this, my anxiety level about working the
DX over the years would have been much lower. Sooner or later, it will be
your turn.
The second thing that occurred to me is that there is no substitute for
crisp operating technique. Call only when the DX is listening. Hear the DX
station before you call.
In any pileup I could hear at least five levels of signals, even when
everyone one was transmitting at the same time.
Based on all of the above, I would tend to disregard any worry over one or
to dB.
But, as was pointed out, over the long haul in a contest it evidently makes
a difference.
There are two other circumstances where 1 or 2 dB makes a difference. EME
communications. We don't strive for that last tenth of a dB noise figure
for no good reason.
The other circumstance in my mind would be digital modes on a "dead" band.
It could make a difference of whether or not the report was decoded.
Just my two cents worth. I have enjoyed the discussion.
73,
Dave, K4TO
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