[TowerTalk] Feeding one antenna in a stack

K3BU at aol.com K3BU at aol.com
Sat May 31 08:31:10 EDT 2003

In a message dated 5/30/03 10:07:50 PM Eastern Daylight Time, 
n4zr at contesting.com writes:

> Now clearly, this result can't be extrapolated to other antennas.  The 
>  C-3Es have an open cell feed, and are short-boom two-element designs.  
>  it DOES suggest is that it isn't sufficient to consider one antenna of a 
>  stack as if it's alone up there, even if you're only feeding that one 
>  antenna.  What you do with the feedlines of the other antennas can make a 
>  real difference.


See if you can model feedlines from antennas that are connected by their 
shields (as just about all antenna switches do) and their centers open and/or 
shorted, and the combinations. 

Similar situation presented problem when I tried to use WX0B StackMatch to 
feed three vertical triangular array, which uses "disconnected" feedlines to 
make two radiators act as a reflectors. Contrary to WX0B claims it didn't work, 
hardly any F/B or pattern - almost perfect "3 el. omnidirectional array". Some 
Eu hams had similar experience and found that you need to disconnect the 
shields too (StackMatch connectors are all mounted on the metal box).

Looks like anything that is conducting within capture area of antennas has 
(hidden) effects and should be considered. This is why I loved my Big Bertha 
with monoband Razors - clean installation, no guy wires, no other (band) 
antennas, just small houses around.

Yuri, K3BU

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