"Frank Gilliland" wrote in message
...
It gives a good idea of the field pattern where it matters. How many
aeronautical CBers do you talk to in any given year

I've been out of town for the past few days and was unable to respond right
away. Anyhow the takeoff angle is of great interest for DX work.Its the
pattern for the main lobes in the antenna pattern that is of interest. Too
high, or too low, and the skip distance is not optimum.

Doing field strength measurements as you outline is fine if all you're
interested in is local contacts. For DX work you have to have a better idea
of the over all antenna radiation pattern, i.e. a 3D plot. That you can't
get with your simple method.

I also take issue with your posted link dealing with antenna resistance
values. You can't calculate so simply. The reason being is the antenna
current is a "standing wave" on the antenna element(s), thus the current is
not evenly distributed. The areas were you have the most lost is where the
current is highest. Going through the math I come up with around 4.655 ohms
compared to your 9.31 ohms. It is still high, but not as bad as the number
you came up with. Other current distributions, from loading coils etc, will
result in other values.

The comments about a 1/4 wave whip being the "best" antenna I'm not so sure
about. I would tend to say that some of the CBer's may have a point when
they claim otherwise. There are two items to consider. One is total over all
antenna efficiency. Second is signal strength at the RX station location.
While the 1/4 wave whip may be an efficient antenna, radiating just about
every watt fed in to it, but if it does so at high angles relative to
horizontal then its nothing but an efficient cloud warmer. Now if you have
an antenna much less efficient than the 1/4 wave whip, but just about every
watt radiated is done so at a very low angle relative to the horizontal the
signal strength at the RX station location is maximized. It there for
becomes conceivable that an antenna design that is not "efficient" as a 1/4
wave whip yet in the area of interest, signal strength at the RX location
because the take off angle is much better, could be a better antenna. I know
a while back this point came up and some of the CBers had some interesting
measurements that tend to confirm such a thing can happen.


--
Leland C. Scott
KC8LDO

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