Gunner wrote:

Over the weekend, I stumbled into a Panasonic RF-4800 general
communications receiver. It looks like it just came out of the box.
Mint+.

I have some issues that perhaps some of you can help with.

First of all, as some of you know, I spend most of the week working
out of an RV in an RV park. The park rules are such that they really
frown on antennas other than TV. So it leaves out a long wire antenna.
My TV antenna (no cable in the park) is about 12' to the yagi. So I
have a mounting height issue..the Slinky trick is out.

Anyone got a good suggestion for a low profile antenna that will cover
broadcast to 31 mhz? Vertically polarized, or
horizontally..horizontal would be best. The RV has a surface aprox 7'
wide by 20' long.

loop antennas are out. No way to turn it from inside and are a bit
high profile.

Second big question. The only place to put this receiver is within 3
feet of my computer. So Im getting freaking huge birdies all over the
spectrum with the puter/monitor turned on.

The receiver has a 50ohm Pl259 coax connector, as well as a binding
post for a long wire. Plus a binding post for AM broadcast and a
third for FM broadcast.

The RV itself is a damned good Faraday cage. Aluminum siding, aluminum
window frames and screen. Even the local stations fade to zip when
the door is closed. I have to leave the cell phone near a window to
work. So the antenna has to be external. Shrug.

Anyone got any suggestions? Ive got a chunk of wire tossed over the
roof at the moment, but tis not particularly effective.

Antenna matching is only for extremely challenging receiving (which this
is not), or for transmitting.

Unless your radio is real crap you'll be receiving atmospheric noise in
excess of the receiver's internal noise with even a moderate antenna.
Atmospheric noise drops off at the higher frequencies, but the antenna
effectiveness will increase for a moderately - sized antenna. If you
really want to disguise what you're doing then mount the TV mast with
insulators, put in a good radial grounding system, and use the whole TV
mast as an antenna.

This scheme requires that you either build a diplexer to isolate the TV
coax outer shield from ground at the lower frequencies or disconnect the
TV when you want to listen to SW. The former will be moderately
difficult but not insurmountable -- I think you could do this with a 1:1
RF transformer and some dinking. The latter will be easy but
inconvenient -- but you can always start with the connection method and
build the transformer later.

The ARRL sells a book on low-profile and hidden antennas. You can go to
http://www.arrl.org for more information, or see if there's an amateur
radio supply store near you. They also sell books on reducing EMI,
which may help with the computer.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com