I use a 1:1 balun mounted on the wall outside the radio room and bring a
short coax line (about 10 feet) into the shack to an ATU. I didn't want to
bring open wire into the shack without preparation (some sort of feed thru
that didn't include my bundle of coax, ground, and rotator control lines).
In the future I may bring it in with a plastic tube without a balun to a
balanced link tuner (an Johnson Matchbox).
See
http://www.dxengineering.com/Parts.asp?ID=883&PLID=253&SecID=78&DeptID={F055
1D82-F47A-4E04-BE2D-BC7CC913768C}&PartNo=DXE%2DWA%2D260 for some
inspiration...
I'm not sure this is the world's greatest all-band dipole, but it seems to
work OK. The instructions supplied come with a formula that helps to
compute an odd multiple of 1/8 wavelength on the lowest frequency (and the
velocity factor of the feedline is an input to this formula).
Your planned supports seem low, but we all do what we can.
Dick, K6KR
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Miller Waco Texas
WB5OXQ
Sent: Sunday, January 15, 2012 4:31 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Dipole fed with balanced line?
I must move my 40 and 75 dipoles due to rfi in the house that I cannot
resolve. I am thinking about 1 dipole fed with ladder line or window line.
I have 2 possable support points.
1 pair is 126' from end to end and 50' high at one end and 30' at the other.
Second pair 139' apart but 25' at one end and 30' at the other. The longer
but lower is farther from the house by about 10' and runs over level yard
with no obstructions. What is up with the 130' dipole fed with balanced
line? Is this better for a multiband antenna than using 1/2 wave at the
lowest desired freq? I have a MT-3000A Dentron tuner which is supposed to
work with ballanced line. The maximum power I run is 800 watts rms not pep.
Suggestions please. I have never used a dipole fed with balanced line.
Will the window line take 800 watts or should I get the open wire feeder? I
really only need this antenna to work on 75 and 40. I use my triband beam
for 20+. How do you bring this line into the shack? Obviously it cannot
touch anything metal along its run. Is the length of the feeder critical?
Should the wire be long as possable or 1/2 wave at the lowest desired
frequency? (3.9mhz) wb5oxq _______________________________________________
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