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[TowerTalk] Breaking up guy wires for nonresonance

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Subject: [TowerTalk] Breaking up guy wires for nonresonance
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Date: Wed, 6 Jun 2001 18:06:44 EDT
   The posts below show the questions that still exist on the need of 
breaking up guy wires.  N7WA got it right.  Some time ago I gave info on TT 
of Eznec patterns I ran of different length guy wires below beams.  I 
concluded from the Eznec and previous 2M test data using a scaled tower and 
guy wires that--if the guy support was Phillistran for a 1/2 wave at the 
lowest frequency of any beam--it could be any length of wire from there down. 
 Eznec showed with the current amplitude function wide open virtually NO 
current on the guy wires 1/2 WL below.  Many have since confirmed this to me 
with actual tests on guy wires. There were ways we checked guy wire RF 50 
years ago with flouresant lamps, neon lamps and light bulbs shunted across 
the guy wires.  Another test is--does the SWR change during rotation?  I 
found with test data that SWR change with beam rotation was often incorrectly 
blamed on power lines and guy wires.  The problem "went away" when a balun 
was added to the coax feeding a balanced 50 ohm feedpoint.  The "RF Spill 
Over" on to the coax shield and to the tower and guy wires was "the source" 
of the problem.  I also had a 20' wood tower guyed with ropes.  The power 
lines 50' away were not the problem.  I added RF anmmeters to a TH-4 
feedpoint, measured the current balance and unbalance with and without the 
balun and watched how the currents and SWR varied with rotation.  This was 
published 25 years ago.  Self supporting metal towers and telephone poles 
also solve a lot of problems.  

A single insulator at the tower for all metal guys is a must and will 
eliminate RF Spill Over transfer to the guys from the tower and coax shield.  
There can still be RF coupling from the beam to a guy directly underneath 
even with the insulator at the tower and a resonant length of a guy like an 
inverted vee.  I found minimum coupling with the inverted vees 10' or more 
below the beam.  The reasons are obvious as explained below and verifiable in 
Eznec.  I and others have run tests with a test dipoles a mile way and have 
run patterns checking for pattern distortion and null fill in.  The most 
sensitive part of the pattern are the nulls which are easy to fill in if of 
the same polarization.  They will fill in by vertical polarization in all 
directions (only if received signal is vertically polarized) with no balun 
and even with a typical Gamma RF Spill Over on to the shield and tower.  With 
beams like the TA-33 without a balun, the TA-33 is mostly a "50 ohm matching 
device for the coax to the tower and guys" (in particular with the metal guys 
attached directly to the tower).
 There is a very straight forward and logical justification for all of this I 
realized over 50 years ago.  This will "ring a bell" if you have ever spent 
time trying to tune up a beam with a FS meter or just varied lengths in 

Consider this: Assume a 3 element yagi on the tower and/or in Eznec.  If you 
add a director and vary it for length and spacing for optimum gain increase 
the most you can get is about 1 dB and it will affect the DE Z some.  In 
order to do this it has to be:
 1. An optimum spacing of around .1-.2 WL.
 2. An optimum length within a percent (on each band).
 3. Of the same polarization
 4. In the same plane in front on the boom
 5. A similar construction of tubing or wire
 Only with all 5 of these "totally optimized" will you get a maximum of about 
1 dB (even less per optimum element the more you add) and some change of 
feedpoint Z.  If anyone is not optimum you will get far less than 1 dB and or 
"nothing" like if the element is not the same polarization and even of the 
right length and spacing.  So you tell me how a guy wire that is not of a 
resonant or a certain length, not in the same plane out front and not of the 
same polarization going to up set the beams pattern or SWR?  If your beams DE 
has a feed system with no RF Spill Over or a good balun is used, you are 
going to go like hell to get a noticeable affect from guy wires unless 
attached to the tower without an insulator and right under the beam.  

With a 1/2 wave of Phillistran from the tower down to a metal guy wire, it's 
totally out of any field that is of any concern.  Scale this in Eznec, rotate 
the beam (that will take awhile). and see for your self.
 Further more beams have a vertical directive pattern that points straight 
ahead.  Therefore the pattern component pointing down at guy wires is greatly 
attenuated and any reflected RF is attenuated again back toward the beam.  
The higher the gain of the beam the more isolated the beam is from 
surrounding objects to the side/back and below.  It just doesn't see them.  
Take a 2M 3 and then a 11 element beam and attach it to a MFJ SWR Analyzer.  
Point the beam at metal objects and then put them on the side/back and below 
the beam and observe what it takes and how close they have to be to affect 
the SWR.  You will get the "isolation message".  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.   Any metal guy wire below that is "out of 
the field of any concern."  Use a 2M beam, scaled tower and guys and run all 
kinds of tests if you still have any doubt.  Also buy the Palomar RF Current 
Meter to measure the RF on wires and tower legs.  I did this 50 years ago for 
my interest, demonstrated it at Convention and Club talks.  Dr Don Reynolds 
of the U of Washington EE Department did the same thing about 20 years ago.
 I have suggested making 1/4 wave verticals using the guys from the ground up 
with radial systems under each guy wire at the ground attachment point up to 
within a 1/2 wave of the tower at the beams lowest frequency.  Since they 
slant toward the tower and are about the right spacing, there can be a "fair 
reflector affect" from the tower.  Now you have a directive 3 or 4 antenna 
system for say 80&40M with no affect to a beam.  If the tower is high enough 
I'd suggest 3 or 4 1/2 wave 40M verticals center fed--no radials needed.  Or 
they can be fed with an L network at the base and no radial system is 
needed--just a ground rod to cool the coax shield.  It's a great system that 
I and other have used.  I've also phased the 2 guy antennas at right angles 
to the main driven antenna to obtain a directive pattern.  One of my next 
long winter projects is to phase in the back antenna somewhat like a "4 
Square" and see if I can minimize even more the affect of the tower in the 
center.  I've already done it using 3 and/or4--l/4&1/2 waves and will 
finalize the results.  The guy wire verticals can be trapped for 80/40M also. 
 I've added another 80M trap at the top and a 160M pigtail back away from the 
tower for resonance at right angles to the guy with great results on 160M.  
It's a way of maximizing everything you have a for all bands if restricted to 
one tower.  Guy wires as antennas has been greatly ignored in ham use 
unjustifiably.  Fortunately no one told me I couldn't use them.  Perhaps this 
will spur some interest in that direction.  K7GCO
In a message dated 6/6/01 9:16:23 AM Pacific Daylight Time, writes:<< 
< Then, I would consider only using Philly for upper guys or near
 antennas depending on how you are going to load the tower. Once you
 get out and/or down a ways, use steel - who says the entire guy
 has to be Philly? (It should be partially steel anyway for
 safety) It really depends on your individual setup. 
 Philly and steel guyed tower owner
 dink, n7wa
***Right on!!  >>
In a message dated 6/5/01 4:44:11 AM Pacific Daylight Time, 
  Guy Insulator Placement   de   N4KG   (Feb 2000)
  The following lengths between insulators have 
  resonances between the conventional bands 
  (which places their resonancesin the WARC bands :-) 
  -  27, 40, 58, and 76 ft.  (per ARRL  Antenna Book)
  You may want to make your wires slightly shorter 
  to compensate for the capacitive end loading of the 
  loops through the insulators.
  You need to place the first insulator as close to the
  tower as possible to prevent coupling to continuous
  wire from one insulator, through the tower, to another
  For the first insulated section, I like to use a short
  piece of 10 to 12 ft between insulators.  This length
  is substantially less than 1/2 wavelength (WL) on
  10M and will therefore be nearly invisible on all frequencies
  below 28 MHz.  For even better isolation, use two 10-12
  ft sections before going to longer spans. 
  de  Tom  N4KG
  On Fri, 04 Feb 2000 02:34:09 +0000 Peter Larsen <> writes:
  > Hi All:
  > Could some one please send me the recommended lengths
  > of guy wires to break up resonance.
  > I know this has been discussed here before, but I just get lost 
  > in the archives.
  > Finally the 100 foot guyed tower is going to go up!
  >  Peter J. Larsen
  >  VE6YC  DO21wc
 In a message dated 6/5/01 6:03:19 PM Pacific Daylight Time, 
 << Thanks for all the helpful replies on my previous question on this 
  One Talkian pointed out that Phillystran isn't that much more expensive than
  steel, and of course does away with all the guy wire resonance problems. I
  didn't believe him at first, but I did some some arithmetic, and danged if
  doing this 74-foot 45G with Phillystran doesn't come out only about $150
  more than using steel EHS, and I wouldn't have to get carpal tunnel
  installing a bazillion insulators. It's amazing how things add up when you
  are buying upwards of 25 insulators, 50+ preforms, several hundred feet of
  EHS, a whole bunch of thimbles, etc. etc.
  So now, whilst waiting for the local power company to mark their buried
  lines near the tower site,  I'm rethinking my position and looking to
  possibly go to Phillystran. Is Texas Towers the only game in town for this
  stuff and it's associated accessories like grips? Nothing against TT, they
  have always treated me well, just wondered if they have a lock on the
  market. Are there any pitfalls or horror stories about Phillystran I should
  Jerry W5KP

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