John wrote:
I believe the advantage you are seeing with a low beverage
is the reduction of pick-up from the feeds. When you think
about it, the 8 foot vertical at each end of the higher
beverage is 1/4 wave on 10 meters and this signal dominates
the signal picked up by the beverage. At lower frequencies
the effect is lesser, but still effects f/b and f/s
signals.>>
------------------------------------
Tom wrote:
If the ends had enough sensitivity to change noise level,
the pattern would be terrible. It all comes back to antenna
pattern.
73 Tom
-----------------------------------------
John replied:
My measurements (done with care) show quite the opposite... that the
reason hardly any of our beverages have the text book pattern is that the
pattern is determined by the vertical component of the feeds. //snip// The
good news is that great front to back and front to side ratios are not very
important unless we are trying to null noise from one particular direction.
Even with only 15 db. rejection, the noise picked up by the front lobe can
be expected to dominate the S/N ratio.
John
K9DX
---------------------------------
Milt, N5IA, commented;
My experience has been strictly with the Beverage antennas terminated WITH
sloping terminations a la Misek's book. That is the way I started doing it
and ALL my installations (permanent, temporary, DX-ped, constructed for
friends, 2-wire and single wire, jungle, desert, mountain rocks, all
terminated) have shown in actual operation to be near textbook in
performance. I have constructed them from 1 WL out to 4 WL at 160 Meters.
They perform equally well from BC band through 40 Meters with excellent
directivity.
>From the locations where I operate most, in SW NM and SE AZ, many times
while listening NE I will catch a syllable or whisper of a call. The
station almost always is located in the 6th or 7th districts and when I
switch to listen on an antenna "beaming" that direction the signal will come
up to S-9 or better.
During late afternoon hours it is real fun to play with signals on the BC
band. Most any time I am able to find a frequency on which I can listen to
THREE different stations, without interference, simply by selecting
different Beverage antennas. There are dozens of frequencies on which this
scenario can be repeated with two stations.
I attribute this (IMHO) textbook performance to the sloping terminations at
BOTH ends of the Beverages. I have made tests with the 8-10' piece of
vertical wire (ie, with the Beverage element disconnected from an elevated
Bev feed end termination) and found it to be a VERY good OMNI-DIRECTIONAL
receiving antenna.
By contrast, I have on a few occasions had a DEAD direction in my array of
two wire Beverages. Upon examination I found the ground connection open on
the far end of the direct to ground terminated element. The attenuation was
on the order of 60 dB, indicating a very good balance in the push-pull
transformer.
I have tried some single wire BOGs and then elevated them slightly through
their length (ends still at ground level). The difference in received
signal levels is miniscule between the two configurations BUT in both cases
is 10-12 dB below same signals from comparison 10' elevated antennas of the
same length. The low level antennas ARE quieter, BUT the signal levels are
comparatively lower also.
Mis dos centavos,
Milt, N5IA
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