If you're just going to use it for receiving, you can use it as is. It
should work quite well. If, however, you have it set in your mind you
need perfection and the value of the loading coil is unknown, you can
scale the antenna whip. It probably still won't be perfect, but since
it is pretty hard to change the coil's physical properties, this might
be the best you can do. Take the center of the band the antenna was
built for (I assume 2M band, which is 146 MHz) and divide it by the
center frequency of the range you want to convert to (162.5 MHz in this
case) and multiply that number by the length of the whip as it exists
now (28"), which gives a new whip length of about 25 and 1/8". Give it
a try...

Scott
N0EDV

A. Pismo Clam wrote:
Hello All,

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.

How long should I cut the whip to accomplish this? Or is the whip too
short already!?

I wouldn't bother the group with such an easy question, but I don't know
where to look for the formula!

Many thanks for taking the time to respond!

Alain