Posted by
Jim Brown-10 on
Aug 29, 2010; 5:49pm
URL: http://elecraft.85.s1.nabble.com/Need-K3-dB-Measurements-on-new-160M-Antenna-tp5468244p5475481.html
On Sun, 29 Aug 2010 12:22:22 +0100, Geoffrey Mackenzie-Kennedy wrote:
>The question remains IMHO whether the data taken from short term "on-air"
>tests over distances which involve ionospheric propagation is useful in the
>first place.
Clearly any such testing requires the averaging of a large number of samples,
and careful comparative tests. That is exactly what I am trying to do -- a
large number of samples, carefully taken and carefully averaged.
For exactly that reason, I am primarily looking for GROUND WAVE tests when
practical. When there are lots of stations on 160M during the daylight hours
(which happens during a major contest), I can regularly work stations over
distances of 800 miles or more if they have good RX antennas and are running
legal power. For example, from my QTH 70 miles S of San Francisco, I can work
stations near Seattle (750 miles), Salt Lake City (600 miles), Phoenix (600
miles), and Denver (950 miles). While there is SOME fading of ground wave, it
is far less than sky wave.
>Unless the vertical patterns of the A and B antennas are very similar in
>shape and lobe take off angle, it can be seen that changes in the angle of
>arrival of the test signal would introduce errors to the results of "on-air"
>tests.
The vertical patterns predicted by NEC for the new antenna and the reference
antenna in the favored direction ARE nearly identical.
73, Jim K9YC
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