Re: CB Antenna Question . . .

[jlandry@domain.elided (John A. Landry)]

The aliens commander decided "Bill Thebert" <bthebert@domain.elided>
would make a perfect specimen for dissection, and he yelled...

>Trying to decide the best place/method to mount an antenna on a standard-cab pickup (8' bed) -- that also happens to have a slide-in cab-over camper installed during the times that I most want to use the CB (long road trips).

Bill,

In a situation like you have (and mine with the Traveler's fiberglass top),
I'm a big fan of antenna mounts that fit in the gap formed by the engine
compartment hood and the fender.  A local CB shop near a truck stop has
these mounts made from stainless steel for a couple of dollars.

Looking at the mount from front or rear of truck once installed, it's like
this (use fixed font)...

                |  A  |
                |  N  |
                |  T  |
                |  E  |
                |  N  |
                |  N  |
                |  A  |
                |-----|
               |-------|
         .---------------------.
         '-------------------. |
               |_______|     | |
                             | |
                             | |
     ______________________  | | ,---------------
                           | | | |  HOOD
              FENDER       | | |______
                           | \________|
                           '---------------------

I mounted my antenna close to the windshield on the driver's side, because
the AM/FM radio antenna is on the passenger side.  You might initially
think having an antenna in your field of view would be distracting, but
just like the AM/FM antenna, you basically look right through it and don't
even see it.

>I can clamp something onto the mirror bracket(s).  If so, should I use one antenna or two?  Need they be tall enough to extend ABOVE the portion of the camper that overhangs the cab?

Mirror mount antenna aren't bad, but I've always *read* (not tested) in
many CB books that popular dual (twin) mirror mount antennas truckers love
need to be separated at least 8' before they really perform properly.  If
they won't be separated very far (small truck), then a single antenna is
just as good.  I tend not to like mirror mount antenna as much, because
depending on the mount, they are sometimes prone to coming loose due to the
repeated door closings.  I also don't like the antenna whipping around
every time I close the door.  Then you sometimes can have increased wind
noise because of the antenna... especially when the window is open in the
summer.  But they are an option if you don't have any other place.

>I could also just stick a mag-mount antenna in the middle of the hood;  or perhaps one of those concealable "fold-down-into-the-trunk" types -- but mounted in the engine compartment.

The one I described above is not fold down.  It's a beefy mount that looks
very professional.

>Lastly, I could mount something SHORT directly atop the camper.  But I'm concerned about this "ground plane" stuff that I don't fully understand.  The camper structure is mostly wood, as far as I can tell.  The "skin" on the outside has a vinyl-like finish, but I can't tell if it's actually aluminum under there or what.  It's definitely non-magnetic.

I'd avoid this myself.  A good ground is very important for proper radio
transmission.  Vehicles are a bad enough platform for an antenna to start
with, and mounting your antenna on the camper is only going to make it
worse.

>If aluminum, will the flat roof of the camper (nearly 6' x 12' I'm guessing) make a good ground plane?  The antenna will have to be SHORT, so that I don't scrape it off on the first overpass.  Drawbacks?  This is the most "central" location, so I think the omni-directional performance would be best (all other things being equal).

The shorter the antenna you're forced to use (like a very short Firestick
or "rubber duckie"), the worse it's going to perform.  Also, the shorter
the antenna, the more electrical tricks the manufacturer must do to make it
*appear* longer to the radio.  Very likely you will not be able to adjust
your SWR (Standing Wave Ratio) down to acceptable levels with a short
antenna.

In a pinch (with no other choice), the aluminum skin will offer some
semblance of a ground plane.  It would be better than nothing.

>If the camper skin turns out to be non-metallic, will the truck body still act as a ground plane, even though the antenna is 4+ feet ABOVE, separated by a mostly non-metallic camper?  Is mounting the antenna atop the camper a foolish idea for reasons I've not yet considered?

Ferrous or non-ferrous metal for the ground plane isn't a concern.  Sheer
mass and size is more important.  If the camper shell is electrically
bonded to the vehicle body, then yes, the vehicle body will assist to some
degree with achieving a proper ground plane.  In your case, probably your
antenna length will be a bigger problem than electrical ground plane
concerns.

As far as antenna selection goes, I prefer something *very* flexible and
non-metallic.  Flexible *metal* antennas will bend if subjected to pretzel
twist when wheeling under a tree or a garage.  The fiberglass Firestick is
a terrible choice because they are stiff and although warranted against
breakage, you risk having your mount ripped off the truck if you drive
under a tree branch at 20 mph.  You must use a spring on the mount with a
Firestick et. al.

That being said, I found an extremely flexible thin fiberglass antenna at
that same local CB shop that sells the stainless mounts I mentioned.  When
I told the shop owner what my requirements were, he grabbed this antenna
off the wall and proceeded to tie it in a knot!  After untying it, it
instantly sprung back to it's original shape.  SOLD!  Since installing it,
I have subjected it to all sorts of abuse and it looks as good as new.  I
never have to worry about where it is and it doesn't need a spring on the
mount.  I forget the exact brand, but I want to think it's Cobra.  Cooper's
on the web doesn't carry this antenna or mount (for some strange reason).
I'd be happy to call the CB shop when they open and get brand / pricing for
both the antenna and the mount.  I could pick them up and ship them to you
if you like.  The shop is a mile from where I work.

Have fun,

John L.
-------------------------------------------------------------------------- 
jlandry AT halcyon DOT com      | 
Conservative Libertarian        |  "The road to  tyranny, we must never
Life Member of the NRA          |   forget, begins with the destruction
WA Arms Collectors              |   of the truth."
Commercial Helicopter - Inst.   |                     William J. Clinton
http://www.halcyon.com/jlandry/ |    10-15-95, speech at the Univ. of CT