On Mar 13, 12:22*pm, (K8JRM) wrote:
Hi Guys,

This is an age old question - what is the best way to get 450 Ohm ladder line
into my shack antenna tuning unit (ATU)? *Here is my situation; I have two 4"
PVC tubes inserted into the exterior wall that allow the entrance of coaxial
cable into my shack. *When I run the ladder line into the shack through one of
these ports, the multi-band wire antenna fed with the ladder line goes wild! *I
can not get the antenna to tune with any of my ATUs.

I have received several suggestions on how I can overcome this problem. *The
most promising one seems to be to use two short pieces of coax with center
conductor connected to either side of the ladder line. These pieces of coax, in
turn, would be fed through the PVC hole into the shack and the center
conductors connected to the ATU. *The shield on the coax would float with no
connection to any thing. *This solution sounds good; however, common sense
tells me that ladder feed line will still suffer because of its proximity to
other objects. Any thoughts on this solution?

Another possibility is using a piece of Plexiglas place under a metal framed
window pretty much as shown in the old hand books. *My problem with this
solution is that the window is on the other side of the room from operating
table, the two coax entry ports and AC power.

Short of placing the tuner outside in the elements, is there a solution to my
problem? *I would be interested in hear what has been tried!

Tom, K8JRM in OKC

Tom, you confuse me. Is the ladder line in the PVC tube all by itself?
Or are there other conductors in the tube with the ladder line? If all
by itself, then there has to be some metal conductor around the PVC.

If the ladder line has to be in a PVC pipe with other wire, Stuff the
PVC pipe full of rags or crumpled newspaper to fill the PVC and raise
the ladder line as far away from the other conductors as possible. See
if that helps.

Another possibility is to put two 1/2 inch pvc pipes inside your 4
inch pipe, split the ladder line down the middle and run each wire
through a 1/2 pipe. Some splicing will be necessary, but your antenna
tuner won't care.

My antenna is a 160 meter lazy quad (horizontal) fed at a corner with
225 ft. of 600 ohm feed line. This line comes through the wall of my
mfg home (aluminum siding) and passes through a DPDT switch to 400 ohm
ladder line to the antenna tuner. The wall insulators are ancient
ceramic units made specifically for feed line through the wall. The
tuner takes care of whatever matching is needed. Works great!

Paul, KD7HB in Oregon