"David Platt" wrote in message
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Also, you might want to read up on actual (as opposed to simple-model)
results with a 5/8-wave mobile antenna, on a typical mount.

I've read a couple of reports which state that the theoretical gain
advantage of a 5/8-wave antenna, over a quarter-wave monopole, depend
a great deal on the 5/8-wave being mounted over a large ground plane
(several wavelengths at least). Without a large ground plane, the
5/8-wave tends to "squint upwards" - its primary gain lobe takes off
at an angle significantly above the horizon, rather than directly out
forwards and backwards from the vehicle. This can result in poorer
signal "towards the horizon" than a quarter-wave would give you - not
good if you're trying to do simplex communication between vehicles,
and maybe-not-good if you're using repeaters (depending how high above
horizontal the direct line to the repeater antenna lies).

5/8-wave antennas are also more prone to "lean back" away from the
vertical when you're driving at highway speeds as a result of air
pressure, and this also can cause the pattern to squint upwards more
than is true for a quarter-wave. The thin "spaghetti noodle" 5/8-wave
antennas such as Radio Shack used to sell (and perhaps still does)
would really have a problem with this, I think.


From years of using several kinds of 2 meter antennas I have found there is
not one that will work best in every case. Several times another ham and I
would swap antennas in the same mount and look at differant repeaters. One
type of antenna would work good in one direction and another in a differant
direction or repeater that is up higher or lower.
Even a 40 meter loaded whip that had a low swr on 2 meters worked beter in
some directions than the other 1/4 to 5/8 wave length antennas.

The thin whip that lays back is not too good. Another one is the ones that
are about 5 or 6 feet long that tend to whip around and give lots of
flutter at highway speeds.

While the antenna programs will show you alot about the patern of the
antenna, it is difficult for them to take into account everything around
them and repeaters mounted at differant heigths. The best is the roof of a
car or van. For the most part if you are in the low rolling hills like
around here , just put a 1/4 or 5/8 on and forget about it.

If you are in an area that is very flat your results may be differant. Where
I am the land is from about 600 to 1000 feet above sea level for the most
part. The repeaters may be from 300 to 1000 feet above that with a few up
to 4000 feet or more above that.

Now that I have been using the dual band antennas there is not really a
choice of what kind to use. Just try to get it stiff enough it does not lay
back or whip around.

All that is based on my and a couple of local hams expierance over the last
40 years.




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