[TowerTalk] Open wire feed line length

w4lde w4lde at numail.org
Wed Jul 2 09:28:39 EDT 2008

After reading several articles both on and off the WEB regarding a 
center fed antenna, only one article mentioned a recommended length for 
the feed line.

My shack is located on the second floor of a new home, (24') #8 ground 
wire to 8' ground stake  with a further connection to the common ground 
point for the power and the rebar in the pored walls and flooring of the 
basement, telephone and cable.  I plan on additional ground rods around 
the property and at a new tower.  In a new home so progress is on-going.

The 1:1 current balum used to convert the 450 ohm balance line is 
external to the tuner, use about two feet of coax  from the balum to the 

Antenna is cut for 80 meters and using about 60-70 ft of line to center 
of the antenna.  Where the antenna lines leave the shack is about four 4 
ft from the location inside of the rig and floor mounted PC.

I use the antenna on all bands until such time I complete a new tower 
installation.  I want to minimize stray RF around the shack since I rely 
on a PC  and digital sound card  as my primary source for ham 
enjoyment.  I have already had some problems with a USB keyboard that I 
think may have been effected by RF when running over 50 watts on 20 
meters only.

One article recommended odd multiples of a wave length is desirable at 
the lowest operating frequency while other articles don't address this.

I am having no problem with a match using the tuner on all bands 80-6 

Have used the center fed antenna since 1976 but always had the shack on 
the ground level and had a good and effective ground system short runs 
with feed lines around the 90 to 100ft in length.  never had a RF 
problem or surge problem.

Any recommended WEB sites or comments are welcomed.

73 de

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