[TowerTalk] 40 mtr dipole spacing above tribander

[Dave Hachadorian]

The D40 is not resonant on 10, 15 or 20 meters, so the dipole should be ok 
parallel to the C3.  I have a 40-2CD six feet above a KT-34XA, elements 
parallel, and all is ok. Those antennas have been there for 30 years, and I 
do pretty well in contests, considering that the XA is at 48'.

The D40 has a broad resonance around 18 MHz, so if the C3 is supposed to 
work there, there will be a problem.  The D40 should be a pretty good 18 
MHz antenna, swr about 2.5, well within tuner-by-Eimac range.

The best way to determine if there is any degradation in the C3 is to do 
front-to-back measurements with a local ham (0.5 mile to 20 miles distant). 
Have him transmit, while you do the front to back.  Procedure is here:
http://lists.contesting.com/archives//html/Towertalk/1998-11/msg00502.html

Do the f/b on the C3 before and after installing the D40 to see if there is 
any change.  F/b is the most sensitive measurement of interaction.

If f/b is degraded, add six feet to the 40 meter feedline and see if it 
helps, or short the 40M feedline while testing the C3.

If that doesn't work, then put the D40 orthogonal to the C3.  If that 
doesn't work, take it down, or add more separation.


Dave Hachadorian, K6LL
Yuma, AZ