[TowerTalk] Antenna interaction question=6m Raibeams Dec 73 mag

[K7GCO@aol.com]

In a message dated 11/12/01 9:45:03 PM Pacific Standard Time, 
wa9wsj@yahoo.com writes:<< 
 Gents,
  I'd like to mount a 6 meter verticle ringo, just above
 my 7 element 6 meter horizontal beam. They will not be
 used simultaneously, but rather, switched between the
 two. Will there be any detrimental effects from one to
 the other? I'm thinking because of the opposite
 polarized planes, it should be minimum or will there
 be an appreciatable amount of capacitive
 coupling/loading to cause problems?
 Thanks!
 Tom
  >>
Tom: A vertical monitoring antenna on 6m is a good idea over a high gain beam 
or ones with good F/B as you can miss openings without it   It attenuates 
local stations ground wave signals that remain mostly horizontally polarized. 
 The Ringo unfortunately has a large amount of RF Spill-Over--Big Time.  
Radials 1/4 wave below the Ring will kill it.  .

 Back in SD I worked a 6m W8 station with a Halo on the side of the tower 
below his 20m beam with a good signal.  I asked about it and he said "he had 
it up for 25 years or so and he could work 2 grid squares ground wave."  That 
caught my attention as that's not all that easy with a beam.

So I took a AEA 6m Halo and added a Clements Match to insure I didn't have 
any RF Spill Over.  The AEA version has a no Xc gamma where the gamma wire 
has to be in exactly the right critical place or the SWR goes to hell.  Even 
pushing on the Halo with a stick changes the SWR quickly as does just 
touching the mounting point which means all kinds of RF Spill Over down the 
coax and mast/tower.

By balancing the 2 feepoints of the Clements Match on each side of center and 
adjusting the series Xc for 1:1 SWR, it's possible to touch the center 
mounting point iwth your hand or a mast and have no change of SWR or RF down 
the mast/tower.  It kicks butt mounted on a tower and in particular over a 6m 
beam 10' and is very quiet.  It's a great Monitoring Antenna.  I've done a 
lot with a 1/2 wave vertical with no RF Spill Over over 2 different 5 element 
6m beams but I prefer the Halo.  When mounted high on top of an already 
existing structure it hears a lot of weak signals.

My next plan is to stack 2 of them about 10' apart and have the lower one 10' 
above the horizontal beam.  One could point forward and one to the rear to 
fill in the weaker part of the patterns or both pointed the same way.  

In the Dec issue of 73 there is a detailed report on the 6m 5 Element Raibeam 
and 2 2 element Raibeams vertically polarized 10' apart 10' below.  The 5 
element forward lobe is sharper than the K8CC 5 element version and the F/B 
is the best I've seen all the way around for any high gain beam.  You really 
need a Monitoring Antenna with this beam as you will miss many signals off 
the back and side on 6m in particular on the DX Monitoring Frequency.  This 
became obvious when rotating the beam and "signals literally leaped out ot 
the noise."  Not many hams ever experience this concept with conventional 
beams.  There were many other performance surprises also.  There was nothing 
to suggest there was a signal there before rotation.  With the 1/2 wave 
vertical on top I could hear them where I couldn't with the back or side of 
the 5 element Raibeam.  

This Monitoring concept was particularly evident on 6m with the Raibeam and I 
have noticed it on 20-10m with 3 element beams and a 1/4 or 1/2 wave 
monitoring vertical on top of them.  I am going to switch to Halo's using a 
Clements Match on 20-10m to see how it plays.  On 20M being of the same 
polarization it will have to be mounted at least 20' above the beam where a 
vertical antenna base can be mounted close to the DE. 

Clements had his match in QST about 35 years ago and it kind of fell by the 
way side unfortunatly.  His version was a bit crude but it worked.on 10M--or 
any band.  It shows up on a commercial beam from time to time  There are 
cleaner ways to construct it.  He tells of not hearing his wifes sewing 
machine motor using it as he did with the gamma.  That's an "impressive test 
or result" that illustates it's doing the balancing act few matching systems 
actually do.      

Rush to the stands and get extra copies of the Dec 73 issue.  There is some 
great photography in it also.  It cost a lot of money and time to prepare.  
K7GCO

List Sponsored by AN Wireless:  AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!!  http://www.anwireless.com

-----
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com