In message , Roy Lewallen
writes
On 8/8/2010 1:17 AM, Ian Jackson wrote:
. . .
Over a perfect ground plane, the 1/4 wave will have an impedance of
around 37.5 ohms, and the 5/8 wave around 50 ohms, so the 5/8 is
potentially a better match for 50 ohm coax. Also, the part of the
antenna which does most of the radiating (1/4 wave from the tip) will be
some 6" higher in the sky and, at 460MHz, if the antenna is mounted low
down, every inch of height above the ground counts! Despite this, in
many situations, you may not find much practical difference between a
1/4 and 5/8 wave.

I found only one practical difference. A 5/8 wave mag mount came undone
on the freeway. I've never had a 1/4 wave come off.

Your magmount obviously wasn't big enough. Was it one of those piddling
2" dia jobs? I've got a 6" limpet, and, with a 146Mhz 5/8 with the 3
turn 'spring' loading coil, there's no was that is going to come off at
any speed (regardless of headwind). Obviously, if the antenna is rigid,
there is more chance of levering it off.
--
Ian