[Elecraft] Metal masts and dipoles etc

[George, W5YR]

Tim, I try to keep the ladderlines feeding my crossed 20-meter EDZ antennas
away from the supporting pushup mast as far as possible without being anal
about it. From the top I bring the lines down at an angle on either side of
the pole to the fascia of the roof where I secure the lines with wooden
clamp blocks leaving enough slack in the line to handle wind movement, etc.

The lines could probably be as close as a few inches to the pole before any
effect would be noticed, but it is just as easy in my situation to keep
them a couple of feet away where they reach the edge of the roof about ten
feet above the ground.

From the point of attachment to the roof edge for strain relief, the lines
are drooped in a rain loop and then back up to the W2DU baluns constructed
in PVC tubing about a foot long for each one. From there coax runs up
through the soffet into the attic and then back down into the shack through
the ceiling in one corner. The coax lines are about 13 feet long.

I do have one balanced line made from paralleled RG-213 that enters along
with several coaxes. Because of the coax shielding, there is no problem
with proximity to the other lines. But plain ladderline should be kept at
least a couple of line widths away from any metallic object or other cable
to be on the safe side.

The problem of course is that objects in the field of the line tend to
unbalance it and provoke line radiation which is then coupled into other
objects and lines to cause RFI, loss, etc. Not a good way to go . . .

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437


Tim and Nancy Logan wrote:
> 
> Hifolks -
> 
> I know this is off subject, but the reflector is such a great resource,
> I hope no one minds. I have a typical sectional steel mast for erecting
> a 30' field mast. How does the metal in the mast impact, for example,
> 75ohm twin lead or 400ohm ladder line running to a dipole?  Or the coax
> running to a Carolina Windom 40? does the feedline have to stand off a
> minimum distance of some sort? Any thoughts would be most appreciated.