On Jan 31, 5:01*am, Ian Jackson
wrote:
In message , Chevy454
writes

In message , dave
writes
But why the trunk lid? Surely the roof is better? On a vehicle, every
inch above the ground helps.

The car is being used for 2M fox hunting. *The Doppler antennas are on
the roof. *The MFJ-1728B is on the trunk lid.

Are you saying that the 6 dB gain of this antenna is not high enough
for a 20 degree tilt to make a difference?

Ken KC2JDY

Noted about the roof already being occupied.

Obviously, if the antenna is 'leaning backwards' at 20 degrees, the
radiation in the forward direction is going to point upwards more than
it would if ie was vertical and, of course, to the rear, the radiation
will point more downwards. However, even with the antenna dead vertical,
the shape of the body of the vehicle will distort the radiation pattern
considerably. I've had a quick Google, and this is one site which
provides some info:
http://www.k6mhe.com/files/mobile_vhf_ant.pdf
There will be lots of others.

This also might be of interest:
http://74.125.77.132/search?q=cache:...st.com.au/Ante
nnas/overview.html+antenna%2Bradiation%2B%225/8+wavelength%22&hl=en&ct=cl
nk&cd=25&gl=uk

As I said, you probably won't notice much difference between vertical
and 20 degrees. But the only way to find out will be to try it.
--
Ian

I think I remember from some place that tilting a vertical monopole
operating against a counterpoise increases the take off angle in both
the direction it is tilted and the direction opposite.

I welcome correction if I am in error.

Jimmie