On 1/6/10 24:15 , Denny "Smitty" Schmidt wrote:
I am renting a trailer house in Minnesota for the winter. I would like to
put up a crude longwire. Any ideas regarding the best way to bring the
leadin into the place with out drilling holes? Could I use coax and close
the window on it without a lot of loss? I have a bunch or RG58 and RG6 and
some 300ohm flat wire around the place.
Smitty
N0NYW



Closing a window on coax is never a good idea. No matter how
thin. There are, however, other options.

Cable installers in the city, where most of the units are rentals
and transient numbers are high, use a short, flat coax jumper
specifically created for this purpose. Connect your round coax to
the flat line on the outside, then connect another round piece on
the inside. Easy solution. Most of the readily available flat coax
jumpers are 75 ohm. The loss will vary with frequency, but in
practical terms for what you want to do, you'll likely not notice.
Universal also has a 50 ohm flat feedthrough jumper. A better,
cheaper solution.

Universal also sells an appliance for this purpose. You set it
in the sill, close the window on it, connect your coaxes, and other
lines, and rock. Made by MFJ. There are two models. Less than $100
for the more elaborate of the two. You move, you take it with you.

You can also make one. A piece of styrofoam will work. Or any
material, for that matter. Lucite, vinyl, even a scrap piece of
bakelite, or 1 X 2. Cut it to size, drill your holes, run your
feedthrough SO-239, close the window and get after it.


All of these tricks will require special sealing of the coaxial
connectors outside the window. CoaxSeal is exceptional for this. And
special window sealing efforts will be required to keep the
Minnesota winter out of your listening room. It can get brisk in
there. But they work, they leave no mark and they're portable.

One of the more elegant solutions, that doesn't require special
sealing efforts at the window, is to use the window, itself, as a
feedthrough capacitor. Depending on the size of the window (the
larger the better), paint both sides of the glass with an aluminum
paint. Or even cover each side with aluminum foil, tightly attached,
and smoothed. Attach a stub to each side of the glass with a
conductive material. The stuff used for repairing automobile rear
window defoggers is perfect. You can find it in auto supply stores.
And some larger drug or grocery stores in the automotive/tool
sections. Once set and dry, cover that junction with epoxy for
sealing and strain relief. Then attach the center conductor of your
coax to the stub on each side of the glass, and ground each shield.
The signal is fed through the glass as the dielectric of a large
capacitor. If the glass is large enough, and the application is
smooth enough, losses are minimal until you get down into the MW
spectrum. When you move, scrape off the paint, or remove the
aluminum foil. No one will ever know you were there.


Enjoy.

p