> This discussion is somewhat tainted by everybody's
> personal experience. And
> I don't think experience translates well from QTH to QTH.
....or installation method to installation method, and by
emotion or feelings since results are tough to measure.
> A discussion of "height above ground" should really be (it
> seems to me) a
> discussion about "height above apparent ground." There is
> a difference.
> Over sea water, ground effectively extends down to what
> depth? Just a
> SWAG--maybe 6" to 12"? I have read of studies where real
> ground can extend
> down 30 feet or more over rocky and otherwise miserable
> ground.
>
> To make empirical evidence comparable from one QTH to
> another, it seems to
> this novice that a beverage mounted 3 feet over some
> typical ground
> characteristic may need to be mounted 20 feet over salt
> water to be
> comparable.
A Beverage will never be in a Beverage mode over saltwater
no matter how high.
That aside, there is no way commonly published to measure
effective depth or conductivity that seems to come close.
When W7EL was here we tried to measure my soil conductivity
and every method radically disagreed with every other
method, and none fit the measured results of a model.
> magical equation. Yet empirical evidence is all over the
> map as far as what
> works and what doesn't work.
Doesn't work is a strong word. When I say a lower height
seems to work better on 40, it is because my higher
Beverages seem to not work as well compared to my 3 element
Yagi as my lower Beverages. Not because they just stop
working. They all work to some extent even on ten meters.
People, especially if they are emotionally intertwined with
their antennas, think because something doesn't work
perfectly or doesn't work like their theory says it means it
doesn't work at all. Take the case of the small magnetic
loop, which really is a magnetic dominant antenna within the
first ~1/8 wave and ALWAYS responds to time-varying electric
fields to some extent. We sometimes want some black and
white magic where the antenna magically sorts bad
"electrical" interference from good signals, but the truth
is once we are out of the induction field area (a small
distance) they are all the same anyway. And at 1/8th wave or
more distant the antenna is clearly electric field dominant
no matter how we build it!
That's where all the fantastic gain claims come from.
Now look at the Beverage. We commonly hear the vertical ends
pick up noise, but there is sad news for those who think
that's the primary problem. The entire antenna responds to
vertically polarized signals. It's a "vertical" receiving
antenna whether we think it is or not. When we aim it at a
tower or pass a vertical tower it can couple quite
effectively, and it responds to signals with the electric
fields vertically oriented. The wire might run horizontally,
but it has vertical polarization.
Even a horizontal T termination used at Beverage ends has
vertical polarization response.
It's a big complex soup of things going on and unless
something is *really wrong* there won't be much difference
in what we do.
One thing for sure, the bigger the antenna the better we
imagine it works, whether it actually does or not.
Especially when our opinions are based on a one weekend
operation.
73 Tom
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