Yuri Wrote:
> Blank statement not valid and overturned by reality.
> Long wire, aka Beverage on the ground works, it has lower
> signal levels but it collects RF signals.
> Done it, have run stealth Beverage on the street and it
> works and provides path to RF signals.
That is entirely out of context for the discussion Yuri. It
is important we keep things in context.
The Beverage Handbook claims a "return wire" below the
antenna functions to inmprove earth connections over lossy
soil. That statement simply is not true. The loss of a
Beverage wire 500 feet long six feet above average ground is
about 6dB. It is much higher s the wire is laid closer to
earth. The wire laid on the ground does NOT form a low loss
return path. It isoply cats like another
Bevererage....although very very lossy. If it acted like a
sensitive Beverage it would OPPOSE the signal from the main
Beverage (they are fed 180 out of phase) and you would have
nothing.
The obvious conclusion is if the wire did anything
functional at all, it can only serve to decrease
performance. It is a terrible idea.
Yuri further wrote:
> Using EZNEC file example of staggered Beverages from W8JI
> web site, they show 79.1 deg horizontal beamwidth at 35
> deg elevation max angle, gain -14.9 dB F/B 15.6 dB
> Removing one Beverage, the single one shows 94.8 deg
> horizontal beamwidth at 40 deg elevation angle,
> gain -13.15 dB F/B 6.49 dB
> 94.8 - 79.1 = 15.7 deg - that doesn't seem like "doesn't
> do as much".
I'm not sure what you are saying because the numbers you
quote disagree with what you say.
We have only a 16.6 percent change in beamwidth while the
F/B ratio changes by a factor almost 10 times!!! The
staggered Beverages on my webpage are not optimum antennas,
but are intended to show how a person with very limited
space can improve F/B ratio significantly by staggering two
short Beverages. There is a SLIGHT change in HPBW (only 16%)
, but the primary improvement is in F/B ratio...just as I
said.
A reasonable length Beverage is already a form of end-fire
array. Since all antenna arrays work by pattern
multiplication the optimum combinations are always when we
mix modes. A broadside pair of Beverages where we mix the
individual antenna's end-fire mode with a new broadside mode
at 5/8th wave or wider spacing gives 3dB or more improvement
in directivity while reducing HPBW nearly 50%.
A staggered long Beverage where we mix end-fire with
end-fire barely changes HPBW but has a large effect on FB
ratio.
This is the same reason it is better to go stacked
(broadside) than to make a Yagi (an end fire antenna)
longer and longer.
> Also statement on W8JI web site that "It is not necessary,
> nor does it do any good, to go beyond 1-1/2 or 2 WL." is
> not true. I have used 3.5 wave beverages and they kill
> other shorter Beverages when signal angles are low.
The fact is I have the space and have had long antennas
installed along with shorter ones for many years. I
gradually moved away from the very long antennas because
they did no good at all compared to shorter (1-1/2 to 2 WL)
Beverages.
It can be proven by taking a clamp-on current meter out to a
Beverage that very little current is left by the time we are
out 2-3WL on the antenna. As a matter of fact up to 50% of
the current is gone at 1 wavelength distance for a six-foot
high Beverage (6dB loss). This means areas of the antenna
beyond that point contribute very little signal and very
little directivity, mostly just adding unwanted minor lobes.
Adding wire where there is not much current left isn't
helpful.
This is actually the same problem with radials. We can keep
making them longer or adding more radials, but once there is
no current left to divide or to spread out we can't gain any
more signal. This is why we know a 6dB gain radial system
gain over a 50 radial system is really just a cover-up for
something else. :-)
73 Tom
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