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[TowerTalk] 40-2CD performance and modeling topics

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Subject: [TowerTalk] 40-2CD performance and modeling topics
From: (David L. Thompson)
Date: Fri, 11 Jul 1997 15:32:50 -0400 (EDT)
Rus NJ2L came up up with model results that are very close to mine. 

1.  No matter what you do ( element tips set for CW, MID or phone the max
gain is just above 10 dbi about 7025Khz.

2. No matter what you do max f/b occurs between 7025 and 7050.  K2WK and I
get more F/B K4JRB (17.9DB), K2WK (19.89) versus at 11.2db.

I set my antenna for mid band and get the following appx.

Freq            SWR             F/B             Gain
-----           ----            ----            -----
7000            2.1             17.0             9.3 dbi
7050            1.7             17.9             9.7 dbi
7100            1.4             17.0             9.0 dbi
7150            1.3             16.2             8.7 dbi
7200            1.3             15.9             8.5 dbi
7250            1.4             14.4             8.2 dbi
7300            1.6             12.8             8.4 dbi

Actual SWR is very close with exact matches at 7 and 7.3.  F/B seems to be
between 12 and 16DB with max at the low end.  On gain...I have done no tests
but I was the first 4 thru to 7O8AA on SSB several years ago and I work DX
with ease.  I think all the modeling programs are useful only for compared
gain as I don't believe any 2 el beam has 9.0 - 2.2 = 6.8DBD gain.  A good
3el maybe but not a 2el!

The antenna is at 87' and the tower is next to the house so its about 51'
from housetop to beam.  There is a KT34XA at 78' below it!                  

Dave K4JRB

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