Jack,
For what its worth, I ran EZNEC on a 40m dipole at 17 feet. I think you said
yours was less than 20 feet up. For a flat top dipole, I got a resonant
impedance of 23 Ohms. When I dropped the ends 15 degrees, the impedance
dropped to 17 Ohms. Sort of in line with what you are getting. Also, with
multiple dipoles the impedance will be less, because you can not completely
ignore the other radiators. Maximum gain was in the straight up direction.
Gain was about 6db down at 25 degrees elevation. On 15 meters, you have 4
lobes offset about 45 degrees from ends/broadside. Gain was about 3db down
at 30 degrees elevation.

Why don't you post your complete configuration. Height at feedpoint, and
length and end point height for the three radiators.

Tam/WB2TT
"Jack Twilley" wrote in message
...
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

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
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (FreeBSD)

iD8DBQFAXtAfGPFSfAB/ezgRAgeFAJ4mwb8Xk5Z0QuPAD3FyooEvhc8t5gCgnEMx
gqrpyBBX4Y0FzaR1VPcnAXI=
=+myT
-----END PGP SIGNATURE-----