I got a connector adapter which plugged into the antenna jack on the back
of
the radio. I connected a VHF magnetic mount ham radio antenna to it. I
now
have a cable running between the bucket seats and out the back door but I
have really good AM/FM reception. On long trips, like across the southern
deserts, I unscrew the standard element and replace it with a longer
element
(about 4') and AM reception is improved dramatically. The cable from the
fender-mount antenna dangles inside the dashboard, unseen and unused.


I have done the same thing with a spare 2 meter 5/8 whip (without the base
matching coil) on the roof with excellent results. The length is little
longer than stock. I used to own an older European car that had a 3 section
whip that was nearly 5' long fully extended and I wish I could find another.
A 102" CB whip will do better on AM (although less optimal for FM). There
used to be CB/AM/FM splitters for truckers, but I don't know how well they
work. The stock whip is far short considering the wavelength, so the
longest you can get on the car will only improve the capture area. As
mentioned, you will notice a peak if you adjust the trimmer in the radio to
your new antenna. They are usually peaked for 1300 kc anyway, so that might
be something to toy with first if you don't mind sacrificing the high end of
the band. An HF antenna with tuner would be the best you could do. In the
campsite, you can clip a longwire on and throw it in the trees.