[Antennas] A Question on Open Wire Feeders

[Pastor-kc1di]

 Hi Kevin,

The reason for noise pick up  on parralell transmission lines is usually do
to imbalance in the line induced often by near by objects, or the ground. 
or if the antenna itself is unbalanced do to one end being closer to the
ground that the other.  sometimes this can be compensated for by giving the
feedline a twist ever so often especially near and metal objects.  also the
line should be kept away from objects, the rule of thum i use is 3 time the
width of the line.  
hope this is of some help,
73 Dave kc1di 

 
-------Original Message-------
 
From: k7rx at comcast.net
Date: 07/29/04 01:31:04
To: ANTENNAS at MAILMAN.QTH.NET
Subject: [Antennas] A Question on Open Wire Feeders
 
Recently, I changed out a coax fed, trap dipole for 80 and 40 meters in
inverted vee configuration which I primarily use for local comms to a dipole
with 60 feet per leg fed with 450 ohm ladder line, also put up in inverted
vee configuration but oriented perhaps 45 degrees differently than the trap
version. I notice this antenna works much better on 30 and 17 meters and
signals seem to be as strong locally on 80 and 40 as they were on the trap
dipole. What I do notice however is a significant increase in pickup of
local noise sources. I am using a current balun hooked to the wall outside
my shack with coax coming through the wall to the tuner.
 
The question I have is why would this particular configuration pick up so
much more local noise than the coax fed trap dipole? I know this feed line
is
superior to what I had and it is a much better multiband antenna but I
honestly don't know why this change should have taken place. From what I
remember of inverted vee patterns, it doesn't seem that a slight change in
orientation could make this big a difference either. I would appreciate any
feedback on this one you all might see fit to give me.
 
Thanks much to all and very 73.
 
Kevin :)
Amateur Radio: K7RX
Navy Marine Corps MARS: NNN0SHS
 
 
 
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