From: (Mad=A0Dog)
I agree as well, a properly engineered single


102" will outperform duals anyday.


Most truckers don't understand how and why


antennas radiate RF energy and they run


duals because they give a balanced look, as a

bonus co-phased antennas tend to


supplement each other on vehicles with plastic

or fiberglass bodies. The fact is that the trailer


blocks a majority of the RF that co-phased


antennas provide to the rear so they end up


with a system that transceives mainly to the


front.


The exception to the rule would be a flatbed


trailer. I use a 102" whip on my T2000 which is

mounted to a flat bar attached to the frame


that extends past the edge of the trailer which


allows the antenna to "see" behind the trailer.


The antenna is supported roughly 6' above the

mounting point using a custom made


plexiglass bracket.


I have also attached 2 braided steel cables to


frame which drag the road during travel and


supply a make-shift earth


ground when parked.


I will be flat honest with you and say that this


system gets out farther then i care for


sometimes.


It also works well for sky-wave propagation


when conditions permit. My 4x4 truck uses a


pedestal mount 102" whip and a 24" x 24"


sheet of stainless,




Congratulations. The "Richochet Skip Dish" has been used for years on
vehicles around here,,practically standard fare on many pickup trucks
'round here. And you're right, it makes one hell of a difference,,,it
gets up and out,,,,.since you have a 4 X 4, pull that bad boy into some
water, like on the edge of the lake or on a beach. Add a Leece-Neville
or two and you're humming.


_
the pedestal is mounted to the floor of the bed


1.5' behind the cab and cut to length with the


top of the bed, the stainless sheet is


sandwiched between the top of the pedestal


and the bottom of the antenna. Very powerful


system using a highly tuned 25 LTD


Mad-Dog




Nice set up for any eleven meter activity. Attaching the mast and
Richochet dish to a steel toolbox is also another popular method. Copper
strap as a ground is preferred instead of wire because of differing
inductance value.

"3 out of 4 people surveyed, belong to 75% of the population."
"Steveo" wrote in message
...
Keith Hosman KC8TCQ wrote:
Steveo wrote:

Frank Gilliland wrote:
In , Steveo
wrote:

Telescopic!! Why didn't I think of that!? It would be multi-banded
since you could just extend it more the lower you went in
frequency.

It's gonna take quite an off-set under the body panel to hold it
all.

:-)

How about a really long door-spring with tubing in the center that
is
connected to a pump, so the antenna can be softened or stiffened as
needed? Just give the pump a few strokes and it rises to it's proper
operating length.....

How about an auto tune option that would self pump..mo money!

sounds like the 11m screwdriver antenna

Did it work for you?

I have never tried one, hell I don't even have an operable CB right now, I
have several old Johnson radios I am restoring, and President Lincoln that
I picked up at a flea market that is a 10m rig that was moded for 11m that I
am building a transverter for 6m to go along with it. I might pick up an
older Unident Grant or an older 148 GTL.



--
--
KC8TCQ
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"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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