[TowerTalk] 40m beam / interactions

[David Hachadorian]

----- Original Message ----- 
From: <corneliuspaul at gmx.net>
To: <towertalk at contesting.com>
Sent: Friday, April 16, 2004 5:00 AM
Subject: [TowerTalk] 40m beam / interactions


> Hello,
>
> if you are talking about interactions between 40m and higher bands
> (15m is worst, 20m is much less affected, 10m is no problem most of
the
> times),
> in my opinion it is not important which brand of 40m antenna you
buy.
>
> It is the simple laws of physics (2nd harmonic, 3rd harmonic, etc.),
> has nothing to do with any brand.

The 2 el Cushcraft does not have a resonance on 15m. This is probably
due to the fact that it has loading coils. I have the 40-2cd just 6
feet above a KT-34xa tribander. Front to back on the XA was not
changed by the addition of the 40m beam. f/b is the best indicator of
interaction, and is easy to measure, with the help of a nearby ham.

The Cushcraft has a broad resonance around 18 mhz though, so it may
affect the Steppir on that band. The Cushcraft is a pretty good
antenna on 18 mhz, with very pronounced directivity.

The newer model Cushcraft has an insulated reflector, and reputedly
has more interaction with tribanders. I don't understand why that
should be, with the two booms aligned, but you could easily ground the
center of the reflector to the boom.


Dave Hachadorian, K6LL
Yuma, AZ