Your antenna is resonant a little BELOW 7.000 MHz.

Is that what you expect?

W1MCE

Jack Twilley wrote:

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The weekend was beautiful, so I was able to do some outside work.

I measured the antenna's impedance over 40m, then shortened the 40m
legs by two feet each. I then measured the antenna's impedance again,
and came up with numbers more closely resembling what I'd expect:

Frequency Resistance Reactance Impedance
7.00 14 6 15.2
7.05 18 15 23.4
7.10 18 21 27.7
7.15 21 20 29.0
7.20 24 27 36.1
7.25 28 36 45.6
7.30 28 43 51.3

These measurements were done using a slightly different method. This
time, I set the noise bridge for R=50 X=0 with the power off, then
tuned the drive on my receiver for maximum noise before powering on
the noise bridge and finding the null. The noise bridge manual is not
as detailed as I would like, and it's not clear what the "proper"
method is, but this produces reasonable results.

The impedance is well within a 2:1 match throughout the voice segment,
and a 3:1 match across the entire band.

In other news, I happened to tune across 20m for the last five minutes
of the Virginia QSO Party, and I made two contacts (NC4S and N4NW).
I feel better about the performance of my antenna on that band, but I
really hope that it's because the tuning somehow helped, and not that
contesters are the only ones willing to dig into the noise.

So it seems like I'm on the right track. I am going to try
lengthening the antenna by six inches and doing another round of
testing before moving on to the second set of legs, unless someone
- From the newsgroup pipes up with a correction to my methodology.

Jack.
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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