No, unfortunately it's not a mith.
When an upper antenna is much larger and not enough far from the smaller
one, althoug not resonant, something bad happens.
In my experience (last one trying to interleave a stack of two 11 element
yagis for 6m among other HF yagis on a 28m tower), depeding by several
factors, the final detrimental effect on the lower antenna exists and can be
more or less pronounced.
Anothe experience showed that a KT34XA, about 13 feet below a 4 el linear
loaded KLM for 40m was definitely not performing like when alone,
independently if aligned or 90° off, and with nearly unaffected SWR curves.
73,
Mauri I4JMY
----- Original Message -----
From: "Pete Smith" <n4zr@contesting.com>
To: <towertalk@contesting.com>
Sent: Monday, January 29, 2001 3:30 PM
Subject: [TowerTalk] Shadowing of small antennas by larger ones?
> Mechanical and wind-load considerations aside, is there a significant
> gain/pattern problem with placing a significantly larger antenna above a
> smaller one on the same tower? For example, consider a Force 12 C-19XR
> tribander, with a Force 12 340N 40-meter antenna (elements roughly 85
> percent of full size) mounted 12 feet above. Force 12 states that
> interaction is no problem because of the design of the N elements. If
that
> is given, then I wonder if there are other considerations. Would the big
> antenna, by its presence, interfere with pattern formation or gain, by
what
> some people call "shadowing." Or is that just another urban myth?
>
> 73, Pete N4ZR
> Contesting is!
>
> The World Contest Station Database
> is waiting for your input at
> http://www.qsl.net/n4zr
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