Here is the result of your feedback to my call for ideas. Thanks to everybody
who responded. Many ideas were to use a vertical type of antenna, but somehow I
was trying to avoid the radials as the grass is mowed by a local farmer and I
am not sure how that would go with all the wires. At least on 80m I was able to
find a solution using vertical loops fed at 1/4 lambda from the upper corner,
so around 23% up from the bottom corner and the use 1/4 lambda 75 Ohm feedline
to bring the impedance down to 50 Ohm.
(Please see below for initial email)
On the big tower I plan to make a 2 el 80m loop towards NA
Hanged between the two other towers will be 1 el 80m loop towards Asia.
The loops are resonating in the EU Phone band. To get them to CW I can add 5 m
stub from each apex hanging down. My question here is how to control the high
voltage relay switching this stub in and out. Can this be done with a 12V wire?
I am afraid of RF interfering with the relay and maybe switching erratically
when transmitting.
Here is the EZNEC file if you want to take a look:
https://www.dropbox.com/s/jbwhnthikkcfozn/2el 80m loop NA and 1el loop AS
S53M.EZ?dl=1
Wires 1 to 7 are 2 el loop
Wires 8 to 10 are 1 el loop
Wires 11 to 13 are towers
Wires 14 to 35 are existing antennas (40m-10m beams and 160m INV V and 80m
slooping dipole).
Anyway this is my idea for 80m. A lot of interference from the towers but I am
not sure how to avoid it.
For 160m I will stay with INV-V 50m high for now and look for a solution during
the winter (
73
Simon, S53ZO
From: Simon Ravnič <s53zo@t-2.net>
Date: petek, 14. september 2018 19:28
To: <topband@contesting.com>
Subject: Call for antenna ideas
Hi!
With a head full of browsing and researching I decided to ask for help this
Topband think tank.
At S53M contest station we are well organized for 40m & up but are lacking
lower band TX antennas.
There are three towers in direction north - south:
- The southern one is 50m high with 40m and 20m monobanders on top
- Middle one is located 25m north of previous one and is 25m high with 15m
monobander and 6/4m duobander.
- The northern one is 28m north of middle one and is 20m high with Optibeam
OB17-4.
There is a possibility to hang anything between them so I think we would prefer
some wire antennas. Already present on the site is 160m INV-V and 80m vertical
dipole from the 50m tower. What we are looking for is 160m and 80m TX antenna
with two main directions 310 and 45 with low angle radiation.
RX antennas are OK as there are three 280m long terminated beverages, direction
270 (Caribbean), 310 (NA) and 45 (AS).
To understand better see a photo of the location at
https://www.dropbox.com/s/bk44cg2zfyzpw3w/S53M.JPG?dl=0
or
https://ibb.co/gRPGVU
Thanks you for your idea & 73
Simon, S53ZO
S53M team
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