RadioBanter - View Single Post

April 8th 04, 09:02 AM

(Diverd4777) wrote in message ...
Question:
How does one make a loading coil for a specific frequency;

You usually use inductive loading to tune a shorter than 1/4 wave
radiator to an electrical 1/4 wave. The amount of inductance needed
will vary as to what freq you want to tune to, and the size of the
radiator. My mobile antenna uses a loading coil. A broomstick, if it
is what I think you mean, is a helical antenna, and is continuously
loaded along it's whole length.

- &
Has anyone made SEVERAL loading coils, switching between them
( all hooked to a long wire)
for better reception on different frequencies

It's much simpler to use one coil, and tap it for the freq to be used.
IE:
My mobile antenna uses a homebrew loading coil "3 inches diameter and
maybe 10-12 inches long" that will tune my 10 ft tall center loaded
whip down to 80m. "3.5-4.0 mhz" But it also has a tap for each of the
higher bands all the way up to 10m. It works all bands 80-10 with one
coil. I just change the jumper from the base of the coil, to whatever
tap I want. I do have to change to shorter stinger whips 12m up, as
my antenna is then full size, and the coil is bypassed by the jumper.
An outbacker mobile antenna is an example of a helical whip which is
tapped for different bands with a banana plug jumper at different
points along the whip.

- What works WORKS !!

It works. MK