hello Bob,
many thanks for the interesting tool calculating dipole dimensions.. it
would be even more useful if it considered insulated wires as well...
PVC-insulated wire can have an additional shortening effect of up to 5
percent (i.e. as much as about 7 ft. one either side on topband)... that may
well be the reason for Paul's problems...
regards
Uli, DJ2YA
----- Original Message -----
From: "Bob K6UJ" <k6uj@pacbell.net>
To: "Topband List" <topband@contesting.com>
Sent: Wednesday, October 31, 2012 12:56 AM
Subject: Re: Topband: Tuning 160M Dipole
Paul,
Here is a handy on line calculator to help you determine the approx wire
length.
You can play with putting in different freqs and see how much the wire
length changes.
I believe with frequency changes of 10KHZ the wire length changes by about
one foot.
So if it is resonant at 1.800 and you trim off one foot it will be
resonant at 1.810.
Note that with the calculator, an inverted V has different lengths than
a horiz dipole
http://www.cdagro.com/dip/dpo.html
If you can find the resonant freq (where the lowest SWR is) then you can
see how far you have to move.
I find this calculator to be in the ball park. I normally cut the wire
lengths long to start with and then prune
till I bring the resonant freq up to where I want it to be. It sounds
like you are resonant below the band right now
which is good, prune time !
73,
K6UJ
Bob
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