[TowerTalk] Detuning Skirt

[n4zkf]

A detuning skirt is to make the tower look invisible to a nearby AM
station so it does not change the radiation of their signal. We have
thousands of them on our towers just for this purpose. I'm not sure why
the skirt is on your tower if IT WAS the AM station itself at one point in
time or maybe I am just not reading this correctly.



73 Dave n4zkf
e-mail: n4zkf at n4zkf.com
web: http://www.n4zkf.com
AR-Cluster node: 145.05 Mhz. or telnet://dxc.n4zkf.com:23
CC-Cluster node: 145.07 Mhz. or telnet://ccc.n4zkf.com:7373
Packet BBS: 145.05 Mhz.-14.098 Mhz. or telnet://bbs.n4zkf.com:6300
BPQ Node: 145.05 Mhz.-14.098 Mhz. (n4zkf-5)
SEDAN Node: 145.770 Mhz. (n4zkf-7)
N4ZKF/R 147.375 Mhz. Tone 103.5






On 8/30/13 8:32 PM, "Roger Parsons" <ve3zi at yahoo.com> wrote:

>
>
>I wonder if anyone has had experience with detuning skirts? (This is
>where a section of tower or other object - usually the bottom - sometimes
>the whole tower - has a cage of wires connected to the tower at the top
>and connected to ground via a reactance at the bottom.) It seems to me
>that in principle any wavelength could be synthesised by the use of the
>proper reactance.
>
>My 160m remote station is based on a 325' former AM broadcast tower. My
>antenna has a half wave vertical spaced about 6' from the tower, with
>some parasitic elements. I feel (without any real proof) that the tower
>is acting as a grounded base 3/4 wave vertical and not helping my
>radiation pattern, particularly the back to front. The total tower height
>is close to 340' when the owner's vhf array right at the top is included,
>and there are also a number of other antennas. The base insulator is
>bridged, and there are 6 or 7 coax feeds going up, all of which have the
>shield grounded at the base and connected to the tower at their high
>points.
>
>I tried temporarily removing the bridge on the base insulator and this
>made no difference at all - just as well probably because it really has
>to be there.
>
>I don't necessarily want the skirt to appear like an open on 160 - I want
>the whole tower to be as invisible as possible on that band. I can see
>how it would be easy to adjust things so that there was maximum rf in the
>skirt, or minimum rf outside it, but I can't see how to adjust it for
>best b/f of my array except by doing remote fs measurements.
>
>
>Sorry I have compressed this - I could bore everyone completely with full
>details if necessary!
>
>Thoughts would be welcome.
>
>73 Roger
>VE3ZI
>
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