[TowerTalk] Tall verticals

[K7GCO@aol.com]

In a message dated 07.04.00 19:41:03 Pacific Daylight Time, n4kg@juno.com 
writes:

<< 
 I recommend  against  shunt feeding tall towers
 with side mounted antennas.
 
 I had a 130 ft R35 tower with a 3L15 on top and 3L20 
 side mounted at 63 ft along with an 80M inverted vee
 at 110 ft.  It worked on 160 but was noticeably less
 competitive after I added the side mounted 3L20.
 I believe it altered the current flow in the tower and
 suspect there was a phase reversal in the upper 
 half, partially canceling the vertically polarized 
 radiation.
 
 de  Tom  N4KG
   >>
Why not try another shunt origination point like higher that compensates for 
what ever additional loading effect the 3L20 had?  Flexible shunt systems 
don't have to be originated at the ground only.  I had 9 on one tower with 
single and double radials (even upper and lower guy wires) with some 
directional affect connected to the coax center lead selected with a home 
made remote coax switch half way up the tower fed with a single heavy coax.  
I compared them to other verticals for reference.  When not used the 
individual horizontal radials were not connected to anything and of the wrong 
polarization to have any vertically polarized pattern affect with the system 
I used.  The selected radial used the tower in a beneficial way. 9 multiple 
shunt feeds on tower the normal way could be a big mess.  I believe the 
system I used also raised the phase center off the ground.  Many of the 
horizontal radials ends were connected to rope guys (no Phillistrand then) 
for supports back in the late 40's.  If the guys were too close I ran the 
additional lengths up and or down or both the rope for resonance.  If 
something is changed that affects an antenna, find a new solution.  Sometimes 
it's better than the previous.  Sometimes the least expected combination 
works real well.  I always have a remote coax switch on a tower for this type 
of shunt loading.  To be effective a configuration doesn't have to be 100% 
vertical or horizontal.  Before Eznec I didn't know what I had and didn't 
care if I could break a pile up.  With Eznec one can see what to expect for 
polarization.  Now I just initially favor any combo with some directivity 
regardless of the polarization percentage.  There is still some cut, install 
and compare--I recommend full time looking for improvements.  The excitement 
and reward of an improvement other than conventional still exists.  K7GCO.   

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