[TowerTalk] Elevated vertical

[Bob Nielsen]

On Oct 4, 2005, at 2:05 PM, K8RI on Tower talk wrote:

>
>
>>
>> Elevated radials SHOULD have the feedpoint decoupled through
>> a common mode choke. if you ground the radial common point
>> is causes increased loss as well as current on the feedline
>> shield.
>>
>
> How would you go about this with an antenna like the AV-640 which  
> has a
> built in tuning network that is grouneded.  Isolate the entire  
> antenna from
> the tower, feed it through a choke, and atach the radials to the  
> bottom of
> the antenna where it would normally atach to the mast driven into the
> ground?
>
> In this case isolating the antenna from the tower is not going to  
> be easy.
> It's only 32 feet, but difficult to get at with *stuff* on the 100'  
> tower
> being much easter to work on.

It's been several years since I installed my AV-640, but I recall  
that the matching unit already has a common-mode choke at the input.

Bob, N7XY