Date:         Thu, 24 Jun 1999 07:53:48 -0400
Reply-To:     EMZ <vw4x4@FYI.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         EMZ <vw4x4@FYI.NET>
Subject:      Antennas Re: CB Disappointment
In-Reply-To:  <015501bebdee$ebf942c0$a35f2299@MSN/dhaynes57>
Content-Type: TEXT/PLAIN; charset=US-ASCII

   Here is the story on any antenna. The length of an antenna is a
function of the frequence that it is being used at. The higher the
freq. the smaller the antenna. CB's run at 27 Mhz. This means that
in order to have a 1/2 wave antenna, you would need a antenna about
204 inches. This would be a rather large antenna so, years ago,
the body of the car was used to make up half of the antenna, and
the antenna was reduced to 102 inch. Then antennas came out with
base loads. This makes the transmitter think that a smaller
antenna is really still 102 inches. Given the above, you must at
all times, keep an antenna, mounted as close to as much metal
as possible. The best spot is right in the middle of the roof.
Keep the antenna insulated, as the signal in the antenna is exactlly
opposite polarity of what is being induced into the body of the vehicle.
This gives you a reflextion, or the signal being repelled, (like to
magnets). What does not get transmitted, goes back to the radio
as heat, (swr). This is bad. It can damage a radio. So you want
to keep this (swr) as low as possible.

            Eric                   86-VW4x4
            vw4x4@fyi.net          72-240z
            Pittsburgh, PA USA     1936-Chrysler


On Wed, 23 Jun 1999, Dennis Haynes wrote:

> Either get that long whip bumper mount antennae or go to a marine supply and
> get an antennae that does not need a ground plane.  An antenna mounted in
> the center of the roof on the front storage rack will also work but not as
> well.
>
> Dennis
>
> -----Original Message-----
> From: Brent Christensen <bpchristensen@MINDSPRING.COM>
> To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
> Date: Monday, June 21, 1999 11:55 AM
> Subject: CB Disappointment
>
>
> >Well, after feeling really proud of my self for having come up with such a
> >cool-looking mount for my K40 CB antenna, I am sorry to say that it does
> not
> >work at all.  :-(
> >
> >I fabricated a mount that clamps around the top horizontal tube of my new
> >Paulchen rack, and then mounted the CB antenna to that.  I used a K40
> >because #1 they have a great reputation (and my CB is a K40) and #2, the
> >antenna base and mast come of with a 1/4 turn bayonet mount.  (Easy to jump
> >out and pop it off to get under parking structures, etc.  I stow it in the
> >long area above the sink and cabinets).
> >
> >Well, after spending many hours running the cable behind the cabinets,
> >fabricating the mount, grounding it to the body, etc. I was rewarded with
> >how really spectacular the antenna looks mounted to the top center of the
> >Paulchen rack.  Unfortunately, there is NO reception.  Nothing.  Nada.  I
> >tested it for ground, and yes, it is properly grounded.  I tested it with
> an
> >SWR meter and it is off the scale (bad).  However, I did suddenly get some
> >weak reception when I had the SWR meter attached.  (???)  I tested out a
> >cheapie magnetic-mount Radio Shack antenna and it got reception, but poorly
> >(until I went and stuck it to the roof of the Cherokee).
> >
> >I didn't realize that the lack of a real ground plane would have such a
> >PROFOUND impact on reception.  How do bumper-mounted antennas work?  I
> >thought the rack and the body would at least provide a LITTLE bit of
> >reception, but I mean there is NOTHING!
> >
> >Any suggestions???
> >
> >
> >Brent Christensen
> >'89 Syncro Westy "Klaus"
> >'95 Cherokee Sport
>