Chuck: You raise some valuable design tradeoff questions. In VHF/UHF
contesting circles, a narrow beamwidth, max. gain antenna with forward and rear
sidelobs minimized to reduce noise pickup often results in missed Q's because
you can't hear a calling station. Most of these design parameters are
tradeoffs dependant on your location: if you have high noise sources then focus
on max. gain, minimum sidelobs, and high F/B ratios. This is particularily true
for EME operators. If you are a zealous 6m op, in a contesting situation, gain
could be traded for wider beamwidths or enhanced sidelobs for max. F/B to keep
Q rate higher and minimize rotor action.
I would think these same design tradeoffs should be applied for the high HF
bands, particularily 10M.
On 10M when pointed to Europe, I've got a noise source to the rear.
Accordingly, my 10M designs emphazize max. F/B ratios at the expense of some
forward gain. This is a design tradeoff dependant on my location. The
important question is for the designer to analyze the design requirements (e.g.
contesting, only 1 antenna on that band, multiplier densities, etc) balanced
against your location constraints and operating requirements
Happy New Year,
Guy Hamblen, N7UN/2 (ex AA7QZ)
---------------Original Message---------------
Frank Donovan wrote:
>
> Anyone out there interested in high performance monoband Yagis???
> I'll prime the pump by sharing the YO file for my 6 element 15M beam on a
> 48 foot boom. Of course, I have YO files for all of my Yagis, and if
> there is sufficient interest, I'll post the YO files for my 40, 20 and
> 10M Yagis.
In Texas,the prevailing school of thought was to build them for max gain
forgetting the front to back because we have no one behind us. However, after
talking to some big gun VHFers out at Field Day, I have decided that on 10
meters this is the wrong approach. I believe there are many times that the
noise level is 10 to 20 db higher off the back of the beam over the desired
direction. With a 10 db or less F to B weak signals in the desired direction
could be masked. Now I shoot for more than 20 db F to B.
73,
Chuck, KE5FI
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