[TowerTalk] Detuning Skirt

[Steve Maki]

You tune for minimum current in the skirt, at least the ones I've had my 
hands on. The tuner and RF sampler is connected between the skirt and 
ground. I've assumed that the skirt and tower become *one* due to their 
close proximity.

The tuning for minimum is quite sharp, which is fine for an AM station 
that never moves frequency. Retuning is required when tower 
appurtenances are modified substantially.

It seems to me that in your case you would tune for minimum on your 
favorite frequency and hope that there is enough detuning effect over 
your desired bandwidth.

-Steve K8LX

On 8/31/2013 3:38 PM, Roger Parsons wrote:

> Sorry Dave, I guess I didn't make myself clear.
>
> The tower has never had a detuning skirft on it, but I am considering
> putting one on. I am aware that detuning skirts are most often used
> to prevent some other structure re-radiating ones wanted signal as in
> the case of your towers and AM broadcast stations.
>
> What I want to do is slightly different. My antenna is not the actual
> tower, but a wire some six feet away from the tower and parallel with
> it. It obviously couples very strongly into the tower, and it seems
> to me that the tower is just about the right size to be 3/4 wave
> resonant on 160m. That is a pretty bad length as (1) it will accept a
> lot of power and (2) its major radiation lobe will be upwards - not
> what is wanted at all.
>
> I believe that a skirt with a series reactance can change the
> resonant point of the tower. What I am very unclear about is how I
> can adjust it - I believe that normally the skirt is tuned for
> minimum current in the tower or maximum current in the skirt. I don't
> think that either of those conditions will necessary be right in my
> case!
>
> 73 Roger VE3ZI