[TowerTalk] Guy Breakers

[Pete Smith]

At 08:05 AM 11/5/02 -0600, you wrote:
>K7GCO has stated that it is necessary to isolate the guys
>for roughly the first  1/2 WL on the lowest frequency of
>ALL the antennas on the tower (i.e. lower guys need to
>be broken up also, especially if you have side mounts).


K7GCO has stated a lot of things.

Tom has wisely said that for best isolation, you should have several sets 
of 10-11 foot insulated sections at the ends closest to the tower.

For what it's worth, I'm not sure that resonance, per se, is really 
important.  It's worth remembering that the conventional wisdom on this 
subject was mostly developed before there was such a thing as 
non-conducting guy material, and before modeling was really in amateur 
hands.  I have modeled my entire one-tower station, and current on 
conductors seems to depend a lot more on proximity to the antenna than on 
length in relationship to the frequency in use.  Are the models perfect -- 
probably not, but they are better than guesswork, I think.  By replacing my 
top guys with Phillystran and using 21-foot insulators on the middle guys 
at the tower end, I got the modeled currents on the guys down to what I 
consider a reasonably small fraction of the current on the antennas.

If I could, I would use all philly, or better yet, all fiberglass.  Tom's 
dead right about the stretchiness of philly, but I suspect that only comes 
into play in pretty extreme conditions.  My 97 feet of Rohn 25 seems no 
wigglier than when the top guys were steel.

A final point -- I believe that Polygon requires a minimum order, but will 
ship fairly minor pieces of that order to different locations.  That raises 
the possibility that again next spring, as in the past couple of years, 
someone on towertalk will organize a minimum order and a lot of folks can 
get in on it.


73, Pete N4ZR
Sometimes a tower is just a tower