#2 would be my last choice.
John KK9A
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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