As I often do, quoting others more expert than myself, the main issue seems
to be detuning of the 15M yagi by the 40M yagi. I asked W3LPL how far a 15
and a 40 should be apart. He thought 30' would be good.
Most of us would not be able to get that much distance and still have them
both rotating on a mast at the top. One of them would either have to be
sidemounted lower down the tower, or you have to accept the potential for
degradation of performance by having them closer.
In the real world, many people put their tribander and 2-el 40 within a few
feet of each other and are satisfied with the performance. Obviously, more
is better. While it's a different situation, different bands, I have 20 and
15 yagis 8' apart and they've always worked well. It's the
interaction/degradation problem that causes people to pair 40/10 and 20/15
on two towers -- alternatively, 40/20 and 15/10. But not 40/15 together.
With a tribander for 20/15/10 that's not the situation you have. 15 is the
one that suffers, typically.
Probably 6-8-10' separation between the tribander and 40 is worth a try and
see if it works satisfactorily for you. The resonant point and/or pattern
of the 15 may change.
You might try putting up the tribander first and do good performance plots
across each of the three bands. Then put up the 40 at whatever separation
you can achieve and repeat the plots to see what effects you can observe.
73 - Rich, KE3Q
----- Original Message -----
From: "Jose Castillo" <N4BAA@cox.net>
Sent: Thursday, August 05, 2004 7:54 PM
Subject: [TowerTalk] STACKING
> I am planning on purchasing a SteppIR 4 element yagi.
> I also have a Force 12 240/230 (2 ele on 40 and 30 meters)
> How high above the SteppIR would be adequate?
> Jose - N4BAA and YI9BAA
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
> any questions and ask for Sherman, W2FLA.
> TowerTalk mailing list
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
TowerTalk mailing list