Howdy Tom

The two short pieces of coax with center conductor connected to either
side
of the ladder line is perhaps the best solution. It was covered in QST/The
Doctor is In, June 2008. In the article it suggests using the best quality
coax on hand, keeping the run to the absolute minimum and the coax shields
should be tired at both ends and connected to the station RF earth. This
configuration introduces a small section 100ohm nominal impedance
transmission line into the antenna system which should have minimal
losses,
but most important is that it is still part of the balance transmission
line. The losses for say RG213 at 4mtr would be almost nothing on 80mtr
and
perhaps up to 2db on 10mtr.
Obviously the lengths of coax need to be exactly the same length.

If you would like a copy of the article drop me email.

Peter VK6YSF

http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm

Hi, Peter.
I read the QST article and thought it was crazy and so I tried
replacing the 5 ft length of ladder line from my antenna tuner up the
wall to the two feed through insulators going through the wall to the
600 ohm feed line outside.

With the 5 ft ladder line I could tune the antenna, a 160 meter lazy
quad loop, to all bands through 15 meters. With the 5 ft section of
double coax, just like the doctor said, the antenna would not tune for
20 meters or any higher band. I put the old ladder line section back.

Remember what all the discussions say about keeping the feed line away
from metal objects? Here we are introducing a 5 ft length of metal
just 1/4 inch from the feed line. The extra capacitance just kills the
feed line. Yes, I was using RG-213.

So, the doctor in nuts, as far as I can tell.

Paul, KD7HB


Paul

That's interesting and noted as I was intending to use that approach to get
the balanced line into my new shack, which is a metal shed. I guess it may
be back the old drawing board. Any suggestions?

Peter VK6YSF

http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm