Topband: Beverage height experiment results

Rick Karlquist
Wed, 22 Nov 2000 09:16:29 -0800

Over the past several years I have experimented with various Beverage
antennas at heights of 5 and 10 feet.  There was anecdotal evidence that the
5 ft ones outperformed the 10 foot ones, and that even lower height might be
better still.  So I decided to do a direct A/B comparison of Beverages at
different heights.  Two identical Beverages were constructed with a length
of 550 feet and spaced 35 feet apart.  They were E-W, aimed East.  A switch
box was used to select A or B or both.  The switch box was connected to the
Beverage transformers through 60 foot pieces of coax.  Both were terminated
with 470 ohms to an 8 foot ground rod, the resistance having been found to
be optimum on a previously built Beverage at 10 feet.

With both antennas at 10 feet, there was no difference noted between them
after checking numerous signals (just a sanity check to make sure they were
really identical).  I then lowered one of the antennas to a height of 2 feet
at the ends, 1 foot in the middle; just high enough to keep it out of the
weeds.  The results of the A/B test were, in a word, WOW!  The improvement
on 160 thru 40 meters between the 2 foot and 10 foot antennas was comparable
to the improvement between the 10 foot antenna and the 90 foot transmitting
vertical for 160M, especially on power line noise.  The drop in gain between
the 2 foot and 10 foot was a few S-units (whatever that means in dB) as
compared to about the same drop between the 10 foot and the transmitting
antenna.  For the first time, I was actually starting to think I need a
preamp. I am wondering if the 10 foot Beverage was working more as a long
wire close to the ground?

I also did some BCB tests for rejection off the side on 1510, 1520, and 1530
kHz.  The 2 foot Beverage was perhaps an S-unit better in this respect.

The second beverage was subsequently lowered to 2 feet and A/B tests now
showed identical performance with the other 2 foot one.

I am now sufficiently convinced of the advantage of the 2 foot height that I
am working on a "quick change" height control system where I can walk the
Beverages and drop the wire height to 2 feet at sunset and then raise the
wire back up to 10 feet at sunrise to get it out of the way so I don't trip
on it.

I have seen various discussions here about putting Beverages at heights
determined by convenience rather than performance (e.g. one posting
suggested the correct height was 1.1 times the height of a deer).  Now I am
wondering if height is more critical than generally believed.

Rick Karlquist N6RK

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