[TowerTalk] Detuning a tower .... was Open-wire transmission line

[Jim W7RY]

There is a site in Portland Oregon (Mt. Scott) that has lots of 
tuned/decoupled towers, because they are near an AM broadcast site. The 
AM station was having issues with their directional patterns.

The de-coupled towers got 3 vertical runs of wire, about 1 foot away 
from the tower, with insulated arms keeping the wires away from the 
tower. At the bottom, they were all tied together with insulators to 
keep them from shorting out to the tower.

Then they were hooked to the outdoor tuning box.

I did not see if the wires were hooked (tied) to the top of the tower or 
not. For a 100' "bulb type" of water tower, they used 4 down conductors, 
hooked to posts about 8 feet high with insulators, then all tied 
together and then to the tuning box.

Apparently it worked.

73, HNY Jim W7RY


On 1/2/2024 12:18 PM, Richard (Rick) Karlquist wrote:
> If you run a wire down the center of a grounded tower, then the tower 
> functions as a Faraday cage so that the wire is non radiating.  It will
> still make a dandy shielded transmission line.  If you run a wire
> along side the tower but outside the tower, then you get the dual modes,
> one radiating and one non-radiating.  Good question though ...
>
> 73
> Rick N6RK
>
> On 1/2/2024 9:49 AM, David Gilbert wrote:
>>
>>
>> Hi, Joe.
>>
>> Detuning a tower and shunt feeding a tower seem to be essentially the 
>> same mechanism except for whether there is a feed or not, and I've 
>> often wondered why running a wire down the center of a tower wouldn't 
>> create the same coaxial section as surrounding the tower with 
>> multiple wires. Has anyone successfully tried this?  I couldn't find 
>> much of anything by searching online.
>>
>> Take care es 73,
>> Dave  AB7E
>>
>
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-- 
Thanks and 73, Jim W7RY