[TowerTalk] Avoiding Grounded 1/4 Wave Guy Sections

[K7GCO@aol.com]

In a message dated 9/29/00 12:02:53 AM Pacific Daylight Time, AD7L@aol.com 
writes:<< 
 Hello All -
 
 Per the ARRL Antenna Book and Handbook, we know what ungrounded lengths of 
 guy wire to avoid.  Also, GROUNDED wires will exhibit resonance at odd 
 multiples of a quarter wavelength.  
 
 My question is how important is it to avoid these resonant lengths of 
 grounded wires, where the grounded wire is the last section of your 
otherwise 
 insulator divided guy.  The ground is to the anchor, which, for a typical 
70' 
 tower, is 56 feet away from the tower itself.  The wire is in a different 
 plane than the yagi up top.  If I wanted to plant a vertical next to a guy 
 wire, I could easily see the negative impact of having a resonant wire 
 nearby.  But for a yagi which is 40 feet or so away from the highest point 
of 
 this grounded wire, how big is the impact?

*************If you have been following TT you would have seen extensive data 
I presented on this very subject.  I modeled it in Eznec using a 10M-7 
element beam on the tower and used different resonant guy wires grounded at 
the bottom and connected to the tower and then one insulator at the tower. 
The bottom line was that is you used a 1/2 WL of Phillistran connected to the 
tower and then for all practical purposes any length to ground, the beam was 
immune to it.  I will send you my findings with all the objections and the 
basic reasoning why the data makes sense and more importantly--is correct.  
It was challenged but not disproved.  Similar tests were done by Dr Donald K 
Reynolds of the U of Wash EE Dept and k4vx who even wrote his own antenna 
software to do tests like this.  I've run tests at my own QTH that support 
what I found also.  So far it's bullet proof.  I will continue to run tests 
with my Palomare Current Meter and FS Meters on resonant and non resonant guy 
wires etc at my antenna sites as an on going program.  

 My particular scenario is for a tower dedicated to the WARC bands (all 
 three), and the last section of guy, which is grounded, is about 30' long.  
 If the actual length is a bit short, there is a resonance on 12M at 28.2', 
 and if the length is long, there is a 17M resonance at 38.8'.
 
 I hate to break the guys up to much more; the cost of insulators and big 
 grips will have me on an extended diet of beans and weenies.

********Perhaps I can save you some money.  This all brings up the concept 
that Ham Radio is getting so complex for the perfectionist that he needs to 
learn how to use Eznec for a host of reasons.  If you do it will answer a lot 
of questions as it did for me.  K7GCO 
 73,
 Ron  AD7L
 Hillsboro, Oregon
  >>

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