Ionospheric skywave signal amplitude or strength is a time-varying random
variable with a mean and a standard deviation.
Difference between strengths of two signals is also a random variable with
an even higher standard deviation, even when originated from the same
location (ever heard of antenna diversity or stacks?), even when originated
from the same antenna on even very closely spaced frequencies (ever noticed
selective fading e.g. on 170 Hz FSK ionospheric signals?). Let alone when
signals originate from different QTHs spaced several kilometers and from
different antennas.
I am not saying RBN data is not useful or meaningful, but to draw a strong
conclusion you have to be sure you take into account that variability.
Based on all variables involved and all possible side-effects, I doubt you
can assess TX power differences below 10-15 dB with a reasonable degree of
confidence just based on RBN data.
Just my 2 cents
73, Juan EA5RS
-----Mensaje original-----
De: CQ-Contest [mailto:cq-contest-bounces@contesting.com] En nombre de Pete
Smith N4ZR
Enviado el: martes, 04 de octubre de 2016 17:16
Para: cq-contest@contesting.com
Asunto: Re: [CQ-Contest] RDXC Entry Reclassified to High Power
Just filling in one bit of info - the RBN-based "evidence" received from the
RDXC did not compare signal reports among multiple RBN nodes, which would
have been meaningless for all the reasons Mike enumerated. They used the
Signal Analysis Tool, which limits each comparison to a single RBN node.
Even doing same-node comparisons would require knowledge of the dozen-plus
variables that can affect the reported SNR at any given moment. N2QT
identified one of the most important and disruptive ones - a much stronger
calling station in near zero-beat, but there are a variety of others. Using
these data to assert that Bob was using high power "for 5 or 10 minutes" now
and then is simply absurd.
73, Pete N4ZR
Download the new N1MM Logger+ at
<http://N1MM.hamdocs.com>. Check
out the Reverse Beacon Network at
<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
On 10/2/2016 11:03 AM, W0MU Mike Fatchett wrote:
> Using RBN to attempt to prove a power violation alone is absurd.
>
> We already know that the antennas are different. 4 Square vs Mono
> Pole Vertical 80m
>
> What feed lines are being used?
>
> How old are the feed lines?
>
> What quality of feed line is being used?
>
> How many radials are being used?
>
> Were the coax cabled installed properly?
>
> What matching systems are being used?
>
> Are there tuners being used at P33W?
>
> Could there be other losses at P33W from bandpass filters, harmonic
> filters, switching, etc.
>
> What power was actually being used at P33W? Is the power limit in
> Cyprus 400 watts?
>
> What are the stations locations to water? Topography, etc.
>
> There could be many other factors that affect why station a is louder
> than station b in the RBN network.
>
>
> What was the reason for looking at P3F's log to begin with? P3F's
> score is 4th in HP. P3F easily wins LP with his score of 12.
> million. He beats 9A5Y by 1.5 million points. However 9A5Y beats
> IQ3IY by almost 2.5 million points. Was 9A5Y's logs checked too? P3F
> had a great score LP. It also appears that the competition for
> whatever reason in LP was not as competitive? It was quite close from
> 2nd place down. It would appear that P3F ran much more than 9A5Y who
> had more multipliers and almost 700 less qsos.
>
> I find it hard to believe that P3F was able to amass 500 extra qso's
> by the accusation of running an amp for 10 minutes here and there.
>
>
> I have no problem with a contest chairman asking an entrant if they
> might have possibly classified their log incorrectly because mistakes
> happen. If contest committees believe that people are cheating then
> provide the proof and it better be more solid than what we have heard
> than this and DQ them. Reclassifying them serves no purpose other
> than to tell us that you "think" they might have done something. To
> me that does not cut it.
>
>
> W0MU
>
>
>
>
>
>
>
>
>
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>
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