[TowerTalk] Breaking up guy wires for nonresonance

[K7GCO@aol.com]

Steve: You are absolutely right on your statements below.  I addressed only 
the one beam on top of the tower.  My 5 conditions zero'd in on it although 
it applies to other beams at a distance for reflections--not detuning the 
beam--they are too far away.  My post mainly addressed the free space pattern 
before ground and other reflections.  If I had multiple beams on a tower I'd 
have Phillistran all the way to about 33' of the ground (a 40M ground plane). 
 Other beams on other towers and their free space patterns can be reflected 
by the guys on other towers but they are too far away to affect the SWR.  So 
SWR change is not a complete test. 

It's easy enough to scale a 2M tower with 2M beams on top, guys and feed 100W 
into it and measure the RF on the guys and other guyed towers.  I found out 
what I wanted to know doing this over 40 years ago and verified it in Eznec.

In the interest of saving money with a single beam on top the idea of having 
Phillistran for a 1/2 wave at least and then a 1/4 or 1/2 wave vertical 
eliminates a lot of grips and insulators and makes use of the guy wires as a 
very effective vertical with some directivity affect from the tower.  There 
are patterns of this in one of the QST Handbooks.  A DX station about 25 
years ago sent me data on this also.  It may not be as directive as a 4 
Square but I'm working on that.  It you have space only for 1 tower it beats 
the hell out of a 4 square you don't have.   

Honda has a 4 wheel dune buggy for the back woods that has some interesting 
accessories.  It has a snow plow which I will need in SD, a ground plow and 
rotatiller for a big garden I plan (fresh health food you know) and some 
other aids.  A single blade from the rotatiller would be ideal for digging 
radial trenches.  It's costing me $600/Mo to get my lawn mowed there again 
this spring and I'm looking at lawn mowers I can pull behind the rig also.  
K7GCO

In a message dated 6/7/01 8:10:02 AM Pacific Daylight Time, 
millersg@dmapub.dma.org writes:
<< K7GCO wrote:
 <snip>
 > RF can bounce off metal objects but unless it bounces back at the "right 
everything in the right plane", the beams pattern and SWR are virtually 
unaffected.  When you run these tests with say a 2M beam and scaled guy wires 
and a tower or in Eznec you will see there has been too much concern for guy 
wires affect except for what is right under the beam for a 1/2 wave.  The 
multiple-insulator 
 > installation all the way to the ground is mostly just another "TT Band 
Aid" 
 > for a problem not properly addressed like poor feed systems used in beams. 
 
 > Fix the source of the problem first.  Unless Phillistran is used for a 1/2 
 > wave from the tower I'd suggest an insulator at the tower, one at 5', one 
at 
 > 15' and one at 30' in metal guys. <snip>
 
 In some cases, K7GCO is right on the mark.  However depending on the 
 installation, there are valid reasons (not "band aids") to use non-
 conductive guy wires (or EHS broken up with insulators) for distances 
 beyond 1/2 wavelength from the tower.
 
 Case 1: Sidemounted antennas
 VSWR and patterns of sidemounted yagis below the top set of guys can be 
 altered even with the first 1/2 wavelength being nonconductive.
  
 Case 2: Multi-tower installations 
 A neighbor had a 18 MHz yagi on a 56 foot freestanding tower that would 
 change VSWR when rotated with |Zin| varying up to 25%! The maximum change 
 occured when pointing at his big tower located about 100 feet away.  After 
 replacing the big tower's EHS guys with Phillystran, the beam's VSWR no 
 longer varied as it was rotated.  Guy wires located about 2 wavelengths 
 away were causing significant interaction.  I believe there is an upcoming 
 article (perhaps in QEX) on the specifics....
  
 Personally, I opted to use fiberglass rod guys (down to ~10 feet above 
 ground level) since I will be sidemounting several antennas.  By removing 
 conductors that are not part of the antenna, any potential guy interaction 
 and reradiation problems are completely avoided. -- 
 Steve Miller   N8SM   millersg@dma.org   http://www.dma.org/~millersg
  >>

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