I've been unhappy with the performance of my NE beverage which often has been
no better than whatever vertical or other antenna I have been transmitting
with. At one time my beverage ran NNE at 15 degrees and I changed it to 30
degrees, but thought that maybe that it was still looking too far north.
Price, W0RI, wrote me that, "if you live in a noise free QTH, the beverage
will not hear as well as the vertical." Greg, ZS6K, kindly sent me an AO
analysis that shows my 700' beverage beamwidth to be over 30 degrees, so it
should work fine to all of Europe.
One of the problems with my beverage is that the signal is so weak, down
6 S-units or more from my vertical. I was straining to hear signals on it. I
found that the homebrew 9:1 balun that KF7MD and I had built 2 years ago was
not working. Removing the balun, I saw no change in signal strength level.
Several of you suggested I use an MFJ antenna analyzer to analyze my
beverage impedance with and without a balun. Duhh. I hadn't thought of
that! I also checked out the ARRL handbook and the ON4UN's Low Band DXing on
winding baluns.
Last night, just before dark, I put a TV balun, one of those cheapy,
6:1, 300 ohm balanced to 50 ohms unbalanced baluns at the end of my 700'
balun. Using the MFJ analyzer, my impedance went from very high to about 15
ohms on 160M and 30 ohms on 80M. According to the analyzer, the SWR was
very high, >10. Still, the cheapy TV balun increased the signal level over
an S-unit at the receiver compared to no balun. It still was quite deaf at
160M altho I did manage to hear and work IT7ZGY and DF2PY with it last night.
It worked better on 75-80M, and the signal strengths of the Europeans was
only down 2-3 S-units on the beverage compared to my Hytower vertical (condx
were excellent on 75M last night) the way a good beverage should perform
according to W8JI.
Today, I wound an autotransformer (se p. 7-18 in Low Band DXing) on the
large toroid core that previously had the balun KF7MD and I had built. Using
a 1K resistor for the load and my MFJ Analyzer, I taped the coil where I got
about a 50 ohm reading. The SWR was about 3:1. I soldered the tap there and
replaced the cheapy TV balun with the autotransformer. The MFY analyzer read
30 ohms on 160M (I forget the 75M and SWR readings), and my beacon 1600 KHZ
Denver station came up over a S-unit compared to the cheapy TV balun.
Tonight I'll see how it works. I think I've recoved 2-3 S-units by going
from no balun to the autotransformer I installed today. And I can probaly
tap the transformer for even more signal.
On another subject- radials. I thought I'd title a post: "Look Daddy!
Mommy shrunk the radials!" Yep, that's sort of what mother nature did
after the three foot snow storm of 10 days ago. Almost all my radials pulled
off the base of my ground mounted 90' tower where they were connected to two
legs of Rohn 25 with muffler clamps. They were connected about 18 inches
above the base of the tower. I had about 10-15 inches of "sag" so that if I
stepped on one, it would not pull off. The thirty six 150' or longer
radials (snow came before I could get more down) had been stamped close to
the ground with my shoes! They were laid in tall grass and probably averaged
an inch or so off the ground. The heavy snow apparently pushed the radials
closer to the ground, especially 2 and 3 days after the storm when it became
pure ice near the ground surface. In any case, the effect was to pull almost
all my radials from the tower. In order to reattach them the other day when
the temp was in the 50's , but there was still over a foot of snow on the
ground, I had to dig out the radials up to 50' from the tower in order to
pull them close enough to reconnect. A few of them I could not pull lose
from the ice- ice pick any one! Anyway, most of them have been reconnected.
For some reason, the resonnant frequency of my antenna has crept up from
1900 KHz to 1930 KHz?
I know my posts are pretty elementary, but I hope they are of value to some.
I sure appreciate getting the advice of those who are technically proficient
and have "been there", but I would also like to read of the successful and
not so successful experiments of others who like me, do not have a whole lot
of technical knowledge and have to learn by doing.
Doug W0AH Colorado
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|