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Items needed:
NGP antenna (FG or LG models), NGP coaxial cable (model K-8NGP), Antenna stud mount
(model K-4)
Introduction
If someone installed a ground-plane dependent antenna system on a vehicle that lacks the metal a ground-plane antenna
needs for counterpoise, an existing mount, can often, be used as a platform for installing a no-ground-plane (NGP) antenna
system. Since our NGP systems are sold as kits, it is unlikely that you will find the individual products readily available
at a communications retail outlet. Your options include purchasing one of our complete NGP kits and using everything but the
mount, locating a dealer that would be willing to special order the parts, or ordering the parts directly from the factory.
Keep in mind that NGP antennas will not work with non-NGP coax assemblies. At a minimum, the antenna and the coax
will need to be replaced. If the previous mount utilized an antenna stud mount made for ring terminal type coax connections,
there is a high probability that the stud mount can be used. Otherwise, if the antenna stud uses the popular thread on
connector (PL-259), it too will require changing.
Most mounts are designed with 1/2" (25mm) stud mount holes. That is a requirement that this procedure is dependent upon.
The Coax
Precautions: Unlike a ground plane system, the NGP system DOES NOT use the coax shield at the mount end. Do not
alter the coax in any way. Be gentle with the coax. No pinching, sharp bending and most importantly, do not remove any of
its length. The NGP coax is a tuned circuit and the length of the main cable establishes the frequency. As for installing
the ring terminal to the coax, soldering is the preferred method. If you crimp the connector on and then later need to
remove it, or make a repair, you will find it very difficult to get the crimped-on connector off without breaking the center
lead.
Route the coax from the radio to the mount. When you arrive at the mount, slip the black rubber weather hood unto the
coax (small end first). Slide the short piece of black shrink tubing over the coax. Place the ring terminal on the
pre-tinned center conductor and solder it in place. With the ring terminal in place, slide the piece of shrink tubing
over the ring terminal post (red insulator), apply heat until it is securely shrunk from the ring terminal all the way
back to the coax.
The Stud Mount
Since you already have a mount, you will need the correct antenna stud mount for attaching the coax and the antenna to
the mount. We suggest using our Firestik model K-4 stud mount. The stud mount is designed to work on mounts with the
standard 1/2 inch hole. Do not install the antenna stud into the mount until you have the coax routed from the radio to the mount.
Start with the stud mount disassembled and ...
- Put the bolt thru the ring terminal on the coax.
- Next, place a flat washer over the bolt.
- Place one of the nylon shoulder washer over the bolt with the raised lip facing up.
- Put the lower assembly you just made up through the 1/2 inch hole in the mount.
- Drop the second shoulder washer over the bolt with the raised lip facing down.
- Place the second flat washer and then the split-lock washer over the bolt.
- Thread the hex-coupling nut unto the bolt.
Before tightening the assembly, make sure that the shoulder washers are centered in the mount hole and the coax is in the
position you want. Tighten the assembly by hand to keep all pieces in place. You'll need a 9/16" wrench and a 5/8" wrench
to secure the stud mount. Do not turn the lower bolt while tightening. Hold the bolt from turning with the 9/16"
wrench and tighten the assembly by turning the 5/8 coupling nut. This will prevent the ring terminal from turning and
possibly causing damage to the ring terminal. Finally, slide the rubber weather hood up to the mount and pop it over the
head of the stud bolt.
The Antenna
With the rubber tip removed from the antenna, unscrew the tuning screw until it is approximately 1/2-inch (12mm) above
the top of the antenna. Spin the knurled locking nut down to the top of the antenna and tighten by hand. This will place
the antenna tuning screw near its mid-way position and offer a good starting point for the tuning operation. Replace the
antenna cap, screw the antenna base into the coupling nut, then hold the coupling nut with the 5/8" wrench and snug up the
antenna (a 7/16" wrench for LG style antenna or 1/2-inch wrench for the FG style antenna).
For maximum performance, and to ensure that the installation was done correctly, the antenna system should be checked
with an SWR meter. Initial SWR measurements, as well as those taken between adjustments require that the antenna cap be
in place. If you adjust the antenna with the cap off and install it afterwards, the SWR will change. Keep in mind that
installation errors as well as extremely high SWR could damage the CB radio if transmissions are made.
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