[CQ-Contest] TH7DXX - SWR improvements ?

DAVE SHARRED dave.sharred at sagem.co.uk
Mon Jun 1 12:45:46 EDT 1998

We have a club (Lichfield ARS) TH7DXX antenna, which is always used for
our contest efforts. It always performs well, but we know the SWR is
always bad on 15, (2:1); and 10m (3:1) in the desired part of a band for

In Eu; I would summarise where you optimise antenna settings on a band
in a contest as follows:

             CW       SSB
20m         14.025    14.225
15m         21.025    21.300
10m         28.025    28.5   (you would obviously expect the antenna
to                               be flatter on 10m)

We have just spent some time trying to reslove these issues;and in
particular on 10m.  The data says that it is resonant (best SWR) at 29.6
MHz ; and that data as published shows the SWR as being bad on, say

We concur these figures, so the antenna works as designed. We tried
lengthening the 10m sections on both the phased driven elements by 3.5"
per side, which seemed to improve 10m (but not conclusive due to an
intemittent that developed - will be fixed this week); and obviously
lowered the resonant freq on 10/20 also. I feel that someone must have
played with one of these and come up with some optimum settings to use.

Does anyone know of a site or any other info with optimised data on
TH7's ??

I would appreciate any help that anyone can give - it is RSGB (and
European Field day this coming weekend; it would be nice to get this
sorted once and for all.

73 Dave   G3NKC  (op at G3WAS. M8X etc)

dave.sharred at SAGEM.Co.UK

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