Two hours before the CQ 160M Contest I finally had my 2 wire 740' NE/SW
Beverage in operation. It seemed to work pretty well, although the Europeans
did not seem very loud, I just figured it was lousy conditions. With the past
contest and a few nights of DX'ing on 75/160M I'm begining to think it should
be working a lot better than it is.
The antenna is a 2 wire 740' (all I can do and stay on my property) and follows
the diagrams that are listed in "The Beverage Antenna Handbook." It is fed
near the center to reduce cable length (XYL says already to much wire on the
ground) and to make a quick job of it, is constructed for 50 ohms and fed
with RG213 about 100' away from the shack. An RCS-8V switches between
NE/SW.
During the 160M Contest, the noise was so high that the Beverage's were used
almost all of the time. Last night I heard a G on 160 and he was S3 on the RX
antenna and S9 on the quarter wave vertical. I then decided to measure the
SWR, and got the following readings;
Mhz NE SW
1.80 1.8 1.6
1.85 2.2 1.3
1.90 2.4 1.2
3.50 2.1 1.8
3.60 1.7 1.7
3.70 1.2 2.0
3.80 1.1 1.8
3.90 1.2 1.4
4.00 1.6 1.5
When listening to EU on 75M, they are just as loud as the 100' inverted vee,
but with much less QRM. (The way it should work) On 80M the signal level
is very low to EU. When switching direction this morning with VK3DZM, he
was almost the same level for both. It seems that an SWR of over about
1.5 seems to degrade the strength of the signal dramatically.
As per "The Beverage Antenna Handbook": The off-center-fed variant uses
he same components as the center fed SWA's and differs only slightly in the
placement of the center termination. As long as the transformer terminations
are used at each end to provide a good match, the center termanation can be
placed anywhere along the antenna without altering the directivity or
performance.
Is anyone else feeding their Beverage's off center like this? Do I need to
start
experimenting with the end transformer terminations to get it matched now?
There seems to be a dip on the SW position where the SWR is less than 1.2
from 3.05 to 3.35Mhz. Would it make sense to lengthen the antenna to get
another half wavelength and get it resonant about 3.650?
Lots of questions, hope you have some answers/ suggestions to help me
in the right direction.
73...Scott K8DX
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