Antennas, lead in etc.
Denny "Smitty" Schmidt
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
Geoffrey S. Mendelson
You can buy a "flat" lead for satellite TV made from very thing coax in a
plastic sheath that will protect it. It's 75 ohm, but still good enough.
Another thing you can do is to put a small strip of wood on the bottom or
side of the Window and drill holes for the coax in it. You then seal the wood
against the window frame with putty, and put weatherstriping on the window
side. If it is cold enough, you can just seal the window to the wood.
Before you mount it, make extra holes for more wires and close them up
with putty that does not harden.
You may not think you need them now, but you never can be sure until you
need to add another antenna, or run counterpoises.
Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel g...@mendelson.com N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.
D. Peter Maus
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
RFI-EMI-GUY
Uh pull the carpet back, drill a couple holes in the floor, and fish the
cable underneath. Watch out for pipes..
--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"�
"Use only Genuine Interocitor Parts" Tom Servo ;-P
Ian Jackson
<dpete...@worldnet.att.net> writes
OMG. What a meal you are making of this simple problem!
If all you want to do is to bring a wire through an opening window,
simply use insulated wire of a diameter thin enough for the window to be
closed on it without causing serious damage to the wire or the window.
The same goes for a ground wire.
--
Ian
D. Peter Maus
I've used this technique, myself. The reason I didn't mention it,
is that it defeats the noise shielding benefit of the coax at
precisely the point where noise becomes a problem: inside the building.
Computers, routers, printers in the room with the radio will leak
noise into the radio's input at the breach of shield. Retaining
shield integrity becomes a practical consideration.
The flat coaxial jumper is much simpler, and does what you
recommend without breaking the shield, and while retaing
characteristic impedance of the line. The connector still needs to
be sealed with something like CoaxSeal for weatherproofing.
The other options, were just those. Options. For the purpose of
demonstration that there is more than one way to fuck a water buffalo.
Ian Jackson
QRM-producing devices will it contain? And the intention was to put up a
crude long wire.
> The flat coaxial jumper is much simpler
Not simpler. However, as you say, it would help with keeping out QRM
coming from within the trailer home. However, to really minimise
interference, it might be best to use the 'remote feed' technique, with
a 9:1 transformer (much discussed in this NG).
>, and does what you recommend without breaking the shield, and while
>retaing characteristic impedance of the line.
Unless the coax is a match for the impedance of the antenna (which it
almost certainly is not), the discontinuity caused by a nip won't matter
at all (provided you don't actually short the coax). Even if it is a
match, it will still be unlikely to be noticed until you get to VHF.
> The connector still needs to be sealed with something like CoaxSeal
>for weatherproofing.
>
Yes, you certainly don't want water in your coax. A generous application
of ordinary contact adhesive (allowed to dry) followed by wrapping with
self-amalgamating tape works well.
> The other options, were just those. Options. For the purpose of
>demonstration that there is more than one way to fuck a water buffalo.
>
Ah - sheer eloquence!
--
Ian
D. Peter Maus
It only takes one.
> And the intention was to put up a
> crude long wire.
With a coaxial transmission line.
>
>> The flat coaxial jumper is much simpler
>
> Not simpler. However, as you say, it would help with keeping out QRM
> coming from within the trailer home. However, to really minimise
> interference, it might be best to use the 'remote feed' technique, with
> a 9:1 transformer (much discussed in this NG).
>
>> , and does what you recommend without breaking the shield, and while
>> retaing characteristic impedance of the line.
>
> Unless the coax is a match for the impedance of the antenna (which it
> almost certainly is not), the discontinuity caused by a nip won't matter
> at all (provided you don't actually short the coax). Even if it is a
> match, it will still be unlikely to be noticed until you get to VHF.
>
>> The connector still needs to be sealed with something like CoaxSeal
>> for weatherproofing.
>>
> Yes, you certainly don't want water in your coax. A generous application
> of ordinary contact adhesive (allowed to dry) followed by wrapping with
> self-amalgamating tape works well.
>
>> The other options, were just those. Options. For the purpose of
>> demonstration that there is more than one way to fuck a water buffalo.
>>
> Ah - sheer eloquence!
You should hear me on Fleet Week.
dave
>
>there is more than one way to fuck a water buffalo.
>
To each his own...