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[TowerTalk] Shunt Feed vs. Inv. L vs. Inv. V on 160-m.

To: towertalk@contesting.com, topband@contesting.com
Subject: [TowerTalk] Shunt Feed vs. Inv. L vs. Inv. V on 160-m.
From: RLVZ@aol.com
Date: Tue, 3 Dec 2013 00:30:26 -0500 (EST)
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hi Guys,
 
Looking forward to getting back on the Top-Band for the next  couple of 
months and working some contests and some good DX.   I'd  appreciate your 
recommendations on the antenna options for my temporary FL  QTH this winter.  I 
don't own modeling software,  nor would I know how to use it if I did, so I'm 
hoping that some of  you will share real-world experiences.
 
At my Florida QTH, I've got a 90' Universal self-supporting  Alumimum tower 
available, it has a 10' top-mounted Aluminum VHF antenna which I  believe 
is DC grounded, therefore a total tower height of 100'.   There are no Yagi's 
on the tower (no other top loading), but no steel guy  wires to interfer 
with the pattern as it's self-supporting.  Radials are  limited due to about 
66' due to space  limitations. On the positive side, the tower is only 100'  
away from a salt water canal on it's East side and the canal runs North and  
South.  Therefore, the tower looks over saltwater to the  North-East-South. 
 
 
Last winter, I "Slant-Fed" fed this 90' tower as follows:  attached a #10 
copper wire to the tower at the 50 ohm point on the tower which  turned out 
to be 25' off the ground and 1/4th the way up the  tower.  The other end of 
the #10 wire runs out 30' away from the tower and  down to the ground level 
to a convenient location.  RG-8 coax feeds the bottom end of this #10 wire 
and a capacitor was  placed in series between the coax and the #10 slant feed 
wire in order to  achieve 50 ohms and J Zero.  (aprx. 250pf)  The coax braid 
 connects to an 8' ground rod and to a half dozen 66'  radials.  I also run 
a 2" copper strap from the tower base to the base  of the Slant-Fed wire.  
(the tower has a lightning ground system which  I believe makes it into a 
brackish salt water because 100 years ago  the  the property was a salt water 
swamp)  
 
Last year's performance of the slant-fed 90' tower was fair to  midland, 
but surely not excellent.  This year I  can repeat the same "Slant-Fed" 
system, or I can hang an Inverted V with apex at  the 90' level which isn't 
dependant on a good ground system, or I can put up an Inverted L with aprx. 85' 
vertical and the rest  horizontal and aiming NE towards Europe.  (If I do  the 
Inverted L, I will be limited to the same marginal radial system of 6- 66'  
radials.
 
Since my radial system is marginal, any predictions  or recommendations on 
which of the 3 antennas would work best for DX?   Again, the 3 options are:
 
1) Slant-Fed self-supporting 100' aluminum tower that has no  top loading.  
(a shunt-fed tower with 6- 66' radials).
 
2) Inverted Vee with apex at 90' and ends  up 20'.
 
3) Inverted L with apx. 85' vertical and the rest  horizontal.  with 6- 66' 
radials).
 
Thanks in advance for your thoughts, 73, and hope to work you  this weekend!
 
Dick- K9OM/4
 
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