Re: Need K3 dB Measurements on new 160M Antenna
Posted by
David Cutter on
Aug 29, 2010; 11:36am
URL: http://elecraft.85.s1.nabble.com/Need-K3-dB-Measurements-on-new-160M-Antenna-tp5468244p5474805.html
Geoff
I was in eQSO with L B Cebik some while ago on a similar tack; basically I
asked how do we test a 4 square design made in EZNEC, say, with on air
experience. He said more or less what you've just said, ie long term
testing over wide azimuth and elevation. I had just designed a passive
array for 80m with advantages over a 4 square.
73
David
G3UNA
> David,
>
> 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.
>
> 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.
>
> I have no experience with 160m, but on 40m for example the change in the
> angle of arrival of short path signals from the East Coast and Midwest can
> be large, and can change rapidly. Sometimes my dipole 70ft AGL which is
> end-on to the States, a "cloud`warmer" in that direction, will outperform
> a 40m beam pointed at the States - a disturbing result if taken to be the
> true performance of the beam.
>
> IMHO "on air " antenna tests need to be repeated many times over a fairly
> long period, preferably with the same stations.
>
> 73,
> Geoff
> GM4ESD
>
>
> David Cutter wrote on Sunday, August 29, 2010 6:36 AM
>
>>I would try a chart recorder in this arrangement; there's no mistaking
>>which
>> channel is which. Of course use a modern version using pc sound card
>> then
>> you can squash up or expand the results for examination.
>>
>> David
>> G3UNA
>
>>> Alas, after years of doing A/B manual coax switch tests, I have given
>>> up on that exposing anything better than 10 db differences on anything
>>> other than stable local signals. And that is suspect because it is
>>> often ground wave, which bears no resemblance to sky wave.
>
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