Mag-mount Antenna

Mag-mount Antenna

Post by Mark » Tue, 05 May 1998 04:00:00

Ok,

I bought the K40 magnetic Antenna used from some one (the 5ft.).  The
magnetic base was all rusted out so I tore it all apart and sand-blasted it.
All of the parts looked like new when I was done.  When I put it back
together I replaced the original foil on the bottom of the magnet with
Alluminum Foil.  I tested the resistence between foil and center bolt with
multimeter and there was almost none.  Then I put one layer of clear plastic
packaging tape on bottom of foil to protect both the foil from tearing and
my car-paint from scratching.  OK here's me Question (finally), will the
tape on the bottom of the foild be a problem because it is plastic and will
not conduct?  I do not know much about Antenna Theory and have heard that a
peice of cloth under the magnet is bad for it.  But have also noticed that
most magnetic antenna's come with a plastic sticker on the bottom to protect
paint.  Would the tape have same effect?

I also was wondering where would be a good starting place on the calibration
of the antenna, as I do not have a meter.  I would like to start in a place
that wouldn't be over 3:1.  I was told a 1/4" from all the way down is a
safe place. Is this true?

Thanks,
Mark

 
 
 

Mag-mount Antenna

Post by t.. » Wed, 06 May 1998 04:00:00




>Ok,

>I bought the K40 magnetic Antenna used from some one (the 5ft.).  The
>magnetic base was all rusted out so I tore it all apart and sand-blasted it.
>All of the parts looked like new when I was done.  When I put it back
>together I replaced the original foil on the bottom of the magnet with
>Alluminum Foil.  I tested the resistence between foil and center bolt with
>multimeter and there was almost none.  Then I put one layer of clear plastic
>packaging tape on bottom of foil to protect both the foil from tearing and
>my car-paint from scratching.  OK here's me Question (finally), will the
>tape on the bottom of the foild be a problem because it is plastic and will
>not conduct?  I do not know much about Antenna Theory and have heard that a
>peice of cloth under the magnet is bad for it.  But have also noticed that
>most magnetic antenna's come with a plastic sticker on the bottom to protect
>paint.  Would the tape have same effect?

>I also was wondering where would be a good starting place on the calibration
>of the antenna, as I do not have a meter.  I would like to start in a place
>that wouldn't be over 3:1.  I was told a 1/4" from all the way down is a
>safe place. Is this true?

>Thanks,
>Mark


This clear plastic (very thin) packageing tape works fine. After
repairing a few magmounts myself this is the tape of my choice
also. It does not have to conduct DC, Only AC which it will if
it is thin enough.
    It doesn't matter where the whip starting place is. If you can't
get the match below 3:1 then the internal capaciter is blown.