I have just found my old Hi-Gain mobile-mount whip antenna, circa
1980's, I'm guessing.

I have just looked at the antenna and it is made in 4 parts; the whip,
the chrome spring that the whip gets screwed into, a metal tube [with a
plastic sleeve covering it. could this be the loading coil?] and lastly,
the mag base. A small quantity of RG 58 is soldered to the underside of
the "loading coil", making a very compact antenna.

If I loosen the set screw in the base and pull out the whip, it is 28"
long; I'd like to cut it so that it will receive/resonate center of the
151-174 MHz band. where I do most of my summer monitoring, using my old
[but still working] BC 210.

If it's an old 2-meter antenna, then I'd guess from the whip length
that it's probably a 5/8-wave, with some form of inductive loading to
make it resonant.

If that's the case, it'll probably receive reasonably well for
monitoring purposes in the 151-174 range without any modification.

Or, you could shorten it by an inch or two, gradually trimming the
whip until the received signal strength around 160 MHz is at a peak.

Another option would be to bypass the loading coil (or whatever it is)
with a wire jumper, and shorten the whip to around 16.5". This will
convert the antenna into a quarter-wave vertical, resonant at around
160 MHz.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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