----- Original Message -----
From: "Rick Ellison" <firstname.lastname@example.org>
Sent: Saturday, June 16, 2007 8:35 PM
Subject: [TowerTalk] Antenna Interaction
> As soon as my rotor comes back from Norm's I will be
> putting my tower back
> up in place . When it goes back up I will be adding a
> home-built rotatable
> dipole for 17 meters. This antenna is going to sit about
> 7' above the A3
> tribander. I am curious if it will make a difference in
> Interaction between
> the two on which way the dipole is lined up. For less
> interaction should the
> dipole be lined up with the A3's elements or with the
It's almost impossible to predict such interactions. f/b
ratio is the most sensitive measure of interaction. Measure
the f/b on the a3. If f/b is degraded, try
lengthening or shortening the dipole's feedline to detune
it, or rotate the
dipole 90 degrees. If f/b is still degraded, you will need
some different antennas.
It's easy to measure f/b:
1. Have a local ham friend 500 meters or more away transmit
2. Turn the back of the beam toward your friend.
3. Note the s-meter reading.
4. Turn the beam toward your friend.
5. Crank in attenuators until the s-meter returns to the
6. Reads the f/b ratio from the attenuator setting.
Dave Hachadorian, K6LL
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