On 12/3/2013 6:52 AM, john@kk9a.com wrote:
#2 would be my last choice.
A thought:
I would think the slant fed tower would have a lower angle of radiation,
but I've had very good luck with a quarter wave, half sloper fed
directly with coax (shield to tower)at the top which is about 95 feet,
but half slopers can be finicky. I tried it, got lucky, and it worked
first time. Very narrow band and IIRC the impedance is about 25 ohms.
I've used the Palstar AT5K tuner in the shack successfully with the
legal limit and no RF in the shack. Although probably not the best
arrangement it's convenient.
73
Roger (K8RI)
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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|