On Mon, 30 Dec 1996 07:57:33 -0000 jan.fisher@virgin.net
(jan.fisher@virgin.net) writes:
>Hello all I wonder if anyone can help with a little info.
>I have a TH7DX at 75 feet with a 402-CD mounted about 12ft above. Both
>booms are in the same plane.
>
>1. The 15m swr curve seems to mimic the plot for normal settings shown
>in the manual but I have assembled it to the DX setting ( in fact the
>only setting given in the manual)...
>I am not that hung up about the SWR on 15m as it is under 2:1 at the =
>bottom of the band however if there is a way to shift the curve a
>little =
>lower it would be nice...
>
>Any other info on your experience with the above setup would be
>welcome.
>
Hi Jan,
One way to see if the two antennas are interacting is to
unground the feedline from the 40-2cd in the shack. See if
the swr profile on the tribander changes. Then short the
shield and center conductor of the 40 and see if the 15
swr profile changes. If it doesn't change, the problem is
probably somewhere else. If it does change, you should change
the length of the feedline on the 40. The 40-2cd elements
by themselves are resonant around 18 mHz (3rd harmonic, with
the added effect of the loading coils). In fact, the 40-2cd
makes a good 18mHz antenna, with an swr of about 1.8. It
is possible, however, to have a particular length of feedline
dangling on the driven element that tunes it to resonance on 15
meters.
Dave, K6LL
k6ll@juno.com
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