Most books or authors state that
> <>over 90% of the times, the arrival signal from EU is 20-23 degrees.
>
>
>Yep. I noted in the 2005 PVRC Contesting Seminar on DVD that W3LPL
>was stating the same thing, 20-23 degrees for Europe and something
>like 15-18 degrees for Japan/Asia and noting that at his location,
>optimum heights for those angles were in the vicinity of 95 to 110
>feet, as opposed to those four 200 foot towers he has.
>
>
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This doesn't sound correct to me. A signal from Europe to W3 land at 90%
probability of arrival at 20 to 23 degrees angle doesn't seem right.
It's also not what is in his outline.
http://www.pvrc.org/Contest_Seminar/Antennas%20-%20W3LPL.htm
In this outline he states for 20 meters to Europe, 5 to 18 degrees, with
no probability listed. I don't know what he actually said in the
presentation.
If you look at numbers from HFTA, which uses statistical data averaged
over the entire sunspot cycle, it will say the 90% point from W3 to Eu
is about 2 to 22 degrees. From Alabama to Eu that number is 1 to 18
degrees.
The arrival angle will vary depending on where you are located. Ga or Al
will not be the same as W3 land. It also varies with the band and the
MUF, which means it changes every hour. The probabilities are also
skewed by the sunspot cycle. When picking an optimum angle you have to
decide if you want the optimum angle over a short period of time or a
long period of time.
The optimum height for an antenna to produce a take-off angle of 20-23
degrees is not 95 to 110 ft. For 20 meters over flat ground an antenna
at 42 ft height has its peak gain at 23 degrees elevation. An antenna
at 100 ft has its peak gain at 10 degrees elevation. Actually a 20 meter
antenna at 100 ft is an optimum height for Europe, but it's not optimum
for 20-23 degrees. It has a null at 21 degrees.
Jerry, K4SAV
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