"Larry Caldwell" wrote in message
.. .
This is sort of an odd question, so I hope someone here can help me with
it. I sometimes take my travel trailer camping in the late fall and
winter, which leaves many hours of darkness to entertain myself. I camp
in remote, unimproved campgrounds, so mostly operate on the trailer's 12
volt system and propane.

I'm installing a sound system in the trailer, and have selected a Dual
XDM6810 car stereo as the receiver/amp. I want to give the radio the
best chance for decent reception in fringe areas, which means figuring
out how to install a good antenna. I can mount the receiver either in
the front or rear, but once the radio is mounted the antenna location is
limited by the length of the lead wire.

1. I plan to install a conventional automotive whip antenna. The top
and sides of the trailer are out because tangling with branches and
brush would tear the antenna off of the trailer. That leaves mounting
on the trailer tongue, the rear bumper, or on a detachable mount of some
kind. Any suggestions? A rear bumper mount would put the antenna
parallel to the metal skin of the trailer for most of its length. Would
that be a problem? I suppose I could also install an electric antenna
through the roof, though that would cost me some battery life and be a
potential source of leaks. I'm looking for advice on location, brands
and types of antennae. Am I overlooking a good idea out of ignorance?

2. What happened to loading coils? When I installed aftermarket
automotive radios back in the '60s, they had a tuning coil. You
extended the whip to the desired length, tuned the radio to a weak
station, then turned the coil adjustment to give the best reception. Is
there an aftermarket loading coil that I could use, or do the
sophisticated electronics of modern car radios not require antenna
coils? The AM sensitivity of this radio is listed at 22 uV, which I
don't recall as being all that great.

Things I have already thought of:

- The propane furnace uses a DC universal motor to circulate air. I
already found an RF choke to install in the power circuit, and can also
put a noise suppressing capacitor across the furnace fan terminals if
necessary.

- This receiver has an external line input and will also read MP3 CDs,
so I can always plug in a satellite receiver or play MP3 CDs.

- I have a Radio Shack DX-440 (Sangean ATS-803A) SW/LW/SSB portable that
will keep me entertained in truly fringe areas.

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Larry,

The general rule with all antennas is to have them as big, high and in the
clear as possible. The ideal location for an antenna would be on the trailer
roof, however you say that this will probably result in the antenna being
ripped off by low branches, etc. The fender or bumper mount puts the antenna
too low and alongside the metal bodywork, so as you have observed, that
isn't a good option.

If you are up for a bit of DIY...

Is it possible to adopt a midway solution and copy the truck driver system
of mounting an antenna on one of the side mirror mounts. This would keep the
antenna low enough to avoid branches, but clear of most of the bodywork.

For sheer robustness and reasonable performance, I have found helically
wound fiberglass whip antennas intended for CB use work well on AM and FM
frequencies. Just change the plug to suit the antenna socket of your radio.
Failing that, a 1 metre length of stanless steel wire (1/8" or 3 mm
diameter) connected to the centre of a coax cable with the cable screen
bonded to the vehicle chassis and suitably weatherproofed can provide good
performance.

The stainless steel whip would almost certainly be light enough to mount on
most wing mirror supports. The hardest part is routing the cable through to
the interior of the vehicle from the wing mirror.

Using a stainless whip also allows additional wire to be connected using a
crocodile clip and thrown up over the nearest tree at your campsite. This
would certainly pull in signals to even the most remote location. My CB
antenna had a small metal tuning stub on the top, so the same trick could be
used.

Mike G0ULI