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Topband: losses on beverages

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Subject: Topband: losses on beverages
From: (DF2PY)
Date: Sat, 16 Oct 1999 16:59:12 +0200
hello topbanders !
While building a new beverage antenna i found a surprising phenomenon.
I have put up a second bev to the US- now to 355 degrees for the northern bends.
The same length as the 315 degree one.Usual design,terminated,unbal/unbal xfrmr 
etc.Matching was not as good as the other one,the SWR was 1:2.2,nothing to be 
really worried about-- i thought.Checking on daytime noise the bevs were
about 4 
to 5 db apart.Checking with AM stns the same difference was exactly measurable.
>From calculations the mismatch cannot be derived.I built another 1 to 12 xfrmr
with another corematerial.This one is flat almost 1 : 1 .And since the daytime 
noise is equal on both bevs,AM stns in between angles are similar in strength.
What can be learned from it,is that even rx antennas need be matched 
perfectly.If i had not had the choice of different bevs of equal length i would 
never have learned about this serious degradation in performance of
a tx antenna you would get away with much less loss at same SWR,but for some 
reason not on a beverage.Whether the problem was the core material loss or a 
certain damage to the function of the bev is uncertain so far.And of course the 
receiving experience showed the same on all dx signals.Maybe this is a way of 
getting a few extra rx-dbs for a few of You out there.              de df2py

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