Dave: The AM station may have been using a folded unipole antenna which
looks a lot like detuning wires. --Mike, WV2ZOW
On Sat, Aug 31, 2013 at 6:06 AM, n4zkf <towertalk@n4zkf.com> wrote:
> 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@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@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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> >
>
>
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