[TowerTalk] modeling interaction

[Michael Tope]

----- Original Message ----- 
From: "Dick Green WC1M" <wc1m at msn.com>
> Hi. I'm trying to use EZNEC 4.0 to determine whether there would be any
> interaction between a 2-el 40m beam at the top of a tower and various 
> beams
> placed lower on the tower. For example, I've tried putting a 40-2CD at 
> 105'
> over a 3-stack of 4-el 15m monobanders at 90'/60'/30'. The model showed no
> significant difference in the 15m pattern with or without the 40m beam, 
> and
> no significant difference in the 40m pattern with or without the stack. 
> Same
> story for 3-stacks on 20m and 10m at the same heights. I even tried 
> putting
> a 5-el 15m beam at 100', only 5 feet from the 40m beam, and got no changes
> in pattern for either antenna. Seems to me that there would be some
> interaction between 40m and 15m antennas spaced that close. Is that
> incorrect, or is there a problem with my model?
>

Dick,

If I am not mistaken, the lumped loading on the 402-CD
causes the 3rd harmonic resonance to fall in the 17 meter
band instead of the 15 meter band as you would get with
a full size element. If you modeled the 402CD correctly,
this might explain why the interactions on 15 are smaller
than expected.

73 de Mike, W4EF..................