[CQ-Contest] Radio Laws of Propagation....Have they been re-invented?

[Edward Sawyer]

Thanks Tor and I agree with you analysis.  It still ties to my conclusions.
In the case of K1LZ vs N1UR, the difference is the amplifier but not much
more.  But it should be more based on the antennas.  I have to assume the
rest is terrain, since I am probably 150 air miles further from the sea than
K1LZ and have a slight polar path disadvantage to a lot of EU.

 

Ed  N1UR

 

From: RT Clay [mailto:rt_clay at bellsouth.net] 
Sent: Friday, February 28, 2014 9:22 AM
To: Edward Sawyer; cq-contest at contesting.com
Subject: Re: [CQ-Contest] Radio Laws of Propagation....Have they been
re-invented?

 

I don't have any comment on KP4KE/NP2P, but I would like to make some
comments re using the RBN data to compare stations:

The procedure of picking two SINGLE skimmer spots at similar times is never
a reliable way to compare signal strengths. Remember, different stations,
even if they are spotted at nearly the same time, are at different
frequencies which may have very different QRM, QSB, etc. Skimmer can measure
properties of a signal, but there is a large fluctuation. This fluctuation
is not necessarily just from propagation differences. I expect the signal
strength reported already includes some averaging over the time skimmer has
decoded the callsign, but more is really needed for accurate strength
measurements.

A good example is the skimmer measurement of phase and amplitude used for
I/Q balance correction (which of course has no propagation difference
issues). The I/Q balance measurements is only possible through averaging a
very large number of signal measurements. In my case I wrote my own code for
SO2SDR to do a similar averaging so I am quite aware of the amount of
fluctuation- it can be huge, even for strong signals! Understanding that you
have to use the data in a statistical sense is important- single
measurements are not very reliable.

To get a meaningful comparison, you need to average a series of skimmer
spots occurring in a short time (< 1 hour?) together. This is most easily
seen using the "Spot analysis tool" on the reversebeacon web page. You want
to look at the average of the measurements over a certain time, not the
peaks or dips.


To give a concrete example from the K1LZ/N1UR comparison, look up
02/15/2014, choose the DF4UE skimmer:

10m : around 1430z: K1LZ fluctuates around about 40 dB, N1UR around 30 dB

15m: draw two horizontal lines through the points between 1500 and 1800.
K1LZ is about 7dB stronger. If you looked at the K1LZ outlier point at 1549z
and compared to N1UR at 1547z, you might think N1UR is much louder.

20,40: similar comparisons can be made, showing 5-10 dB in favor of K1LZ.

80,160: not enough data here

 

So yes, N1UR may have a good qth, but I think skimmer data does show that
K1LZ is nearly 10 dB louder into Europe in this case on all bands.

 

Tor

N4OGW/5