Hi Lance!
My 160M phased Beverages consist of two identical 580 foot Beverages, 7
feet high, spaced side-by-side by 270 feet. Each is fed with identical
Minicircuits Laboratories T9-1 transformers and identical 140 ft RG-213
feedlines. I simply connect the two feedlines to my 1000 foot RG-213
transmission line by using a T-connector! A purist might use an
additional 2:1 transformer, but I have experienced no discernable
degradation by not using the 2:1 transformer. The performance of a pair
of 580 foot phased Beverages is very similar to a single 1160 foot
Beverage.
Regarding your second question, Beverage antennas are very inefficient and
as a result the noise figure of a receiver system using a Beverage antenna
degrades significantly above 7-10 MHz. To combat this inefficiency,
a 10-30 MHz Beverage array might consist of three (or more) 220 foot
Beverages, four feet high, separated side-by-side only four four feet
from each other. Such an array typically has 3 dB improved efficiency (not
gain!) relative to a single Beverage of the same height and length. I
would not expect any significant benefit from such an array on 80 or 160
meters because Beverage inefficiency does not usually limit receiver
system sensitivity at this frequency due to high ambient atmospheric noise
levels.
Because Beverage antennas are inefficient, the mutual impedance
between the close spaced Beverages is negligible, as a result the
feedpoint impedances are only slightly affected. A simplified (but
effective) feed involves bringing the three close spaced wires together at
each end of the array. The resulting feedpoint impedance is 150 ohms and
can be fed thru a 3:1 transformer and the termination is simply a 150 ohm
resistor to a single ground rod.
73!
Frank
W3LPL
donovanf@sgate.com
On Wed, 30 Apr 1997, Lance Johnson wrote:
> PHASING - A few of us are intrigued by your phasing of two 580'
> Beverages. We have the real estate, but to be quite blunt no one has
> figured out a proper matching method.
> 73, K0CS
>
> NOTE: Three Beverages separated by the distance above ground gives 3db
> gain - that is also intriguing but how do you phase them?
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