On Nov 3, 9:27 pm, Dloyd Lavies wrote:
On Nov 3, 5:54 pm, "John Doe" wrote: If you can't contribute anything positive to this question, then stay out of
it, with your trash!

I have a 10m base loaded mag mount antenna, that I had to put a piece of
felt over the magnet as not to scratch a new vehicle.

You are wasting your time trying to protect the paint when using a
magnetic mount. Grit will find its way under your magnet, and within
a year of normal driving, you will have scratched paint. Take a deep
breath, get out the hole saw or metal punch, and punch a hole in your
new car. Your radio will be happier and so will you as the paint
around your antenna will not be subjected to the inevitable damage
caused by magnet mounts. BTW, before anyone says anything about
lowering the value of the vehicle, I've sold and traded-in multiple
vehicles with holes punched in them, and not once has anyone ever said
a word about the holes. When I trade it in, I just put in a rubber
plug and no one notices.

When I did this I apparently changed the capacitance between the mag mount
and the roof of the vehicle. Someone suggested that I might want to replace
the felt with either a large balloon or a large prophylactic as it is
thinner and the capacitance would then return to almost where it should be.

Positive comments only!

However, if you have committed yourself to using a magnetic mount, I
would suggest using ultra thin vinyl sheeting, this should give you
enough grip to keep it on the vehicle. Nevertheless, anything that
you use is going to require that you retune the antenna, a longer whip
may be also be required because of the decreased capacitance.

73, Dloyd

Try some 3mil Teflon, Teflon has a very high capacitive coefficent.

Jimmie