Re: Yagi height above ground
- From: "Rick (W-A-one-R-K-T)" <get.my.email@xxxxxxxxxxxx>
- Date: Mon, 10 Sep 2007 13:04:38 -0400
On Mon, 10 Sep 2007 08:51:56 -0500, amdx wrote:
I see that height above ground affects the gain and the angle of the
main lobe. (actually all lobes) The info I've seen shows best gain and lobe
formation somewhere between 1/4 and 1-1/2 wavelengths above ground.
So I have a 2.4Ghz yagi, does that mean I should put it 1/4 to 1-1/2
wavelengths
above ground? That means it would be 1-1/2" to 6" above ground.
Good afternoon, Mike.
1/4 wavelength above ground seems might low to me in any case... it's only
16 feet on 20 meters.
I think that any such numbers you find, though, should be considered
minimums. Higher is generally better.
For example, 1-1/2 wavelengths at 20 meters is 100 feet. Now, that's
mighty effective height for a 20-meter beam, but I don't buy that it's
more nearly optimum than, say, 150 feet. I might believe that perhaps
once you get above 1-1/2 wavelengths at non-line-of-sight frequencies,
anything more may be an exercise in diminished returns.
As for your example at 2.4 GHz, don't forget that 2.4 GHz, like all UHF
and most VHF bands, is a line-of-sight band. You don't generally get skip
like you get on HF and low VHF. So, comparing, say, 14 MHz to 2.4 GHz in
terms of antenna performance vs height above ground isn't a valid
comparison.
.
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