I set out to install a C.B. radio on my 2003 Nissan Frontier King Cab, and was first faced with the decision of where to place the antenna itself. The middle of the roof panel is always the best place, but for the sake of a more novel approach, I set out to place the CB antenna in place of the original FM antenna. This is a practical location, yet no seamless off-the-shelf mount exists.
Placing the antenna on the vehicle roof or hood is a great way to provide your antenna's ground plane. Ground plane is essentially a reflecting surface which is both connected to the antenna ground (vehicle ground, negative battery terminal) and is generally made up of your vehicle's outer body panels. Availability and arrangement of ground plane affects antenna range and directionality.
Nissan Frontier in need of Citizen's Band:
Below is the vehicle fitted with four foot of C.B. antenna where the FM antenna would normally reside. The antenna is the Firestick FS4-B, mounting stud is the Firestik K4, spring is the heavy-duty plated Firestik R-3H (not pictured below), coaxial cable is the Firestik K-8, and the C.B. radio is the Midland 75-822. The mounting stud is the element which is fastened to a custom mount which replaces the FM antenna mount, and for which I have provided drawings herein. This mount is low-profile and not only provides the 1/2" minimum of clearance for the 3/8-24 hex cap screw of the K4 mount but also keeps the top part of the K4 mount (the female threads that accept the antenna or spring) just beneath the windshield cowl of the Frontier. The C.B. handpiece is hidden inside the center console top lid and can be easily detached and used as a portable unit.
Existing Mounting Holes and Hardware
The Nissan Fronteir has an AM/FM antenna mount held in place by two sheet metal screws. This mount is not compatible with threads found on C.B. antennas, nor the Firestik brand antennas (it is very light duty, perhaps 1/4-28 thread). This mount is pictured below in the lower right of the frame. To get to the mount, remove the caps on the windshield wiper bases, remove the windshield wipers (12mm nuts), and forcibly pop off the windshield wiper cowl with a large flathead screwdriver. In the upper left, the hole in the cowl that the antenna must project through is shown. It is much larger than the antenna and you may choose to add a grommet, although I did not feel the need to.
Firestik FM to CB Antenna Mount Drawings
The mount which must be fabricated can be designed by copying the footprint of the existing FM antenna mount and augmenting it to fit the CB stud mount. However, the FM mount is an unnecessarily complex shape and can be boiled down to a fairly rectangular form which is easy to machine. My drawings follow and detail a shape of the CB mount which can replace the original FM antenna and not require any adjustment to any other part, including the windshield cowl. The chamfer called out on the lower left of the main view may not be necessary but provides a minimum of clearance for a nearby obstruction. Similarly, no material should be added north of the antenna mounting hole as pictured below in the main view.
The above print describes the most basic replacement. Adjustment for rake present in the hood/body panel of the 1999-2004 Frontier has not been compensated for.
The above print compensates for the tilt present naturally in the hood/body panel of the 1999-2004 Frontier. These angles have been approximated visually, and have resulted in a functional and well-aligned antenna in practice. No more than 3.5 degrees should be expected to result in a perfectly vertical antenna, based on my best estimate.
The 3/8-24 hex cap screw, which conducts the signal from the antenna to the hand piece, should not be allowed to come in contact with the mount (ground). This can be prevented by placing a couple layers of electrical tape or plastic shims between the two parts. The assembly should be tightened and tested before putting the windshield cowl back on.
Post-Install C.B. Mount
Below are a few pictures depicting the final install with the new mount and a couple more illustrating how the top of the mount is approximately flush with the windshield cowl. On top of the mount, a spring is placed before adding the antenna. I recommend a spring if you ever intend to use both a four foot + antenna and simultaneously enter a parking garage.
These photos depict a wire with black insulation grounded to one of the mount screws. That is actually a jumper to the body of the old FM antenna mount, which had been packed away into the interior of the body panel. This ensures that the conversion can always be reversed, and that some signal can still be had from the AM/FM mount despite the antenna missing. Surprisingly, I still do receive many radio stations with this arrangement. I rarely listen to the radio, but if I did, I might consider a splitter.
To be continued...
Reception has been very good since installing the antenna and tuning the antenna with an SWR meter. Range is definetely falling at least within the 4 mile radius from the vehicle (a conservative guess, as some days there seems to be so much chatter that a greater range seems more likely). Most other vehicles with C.B. radios are truckers with a few other familiar voices perhaps belonging to a nearby base station. The Midland 75-822 has the option to use the 8" rubber-ducky antenna outside the vehicle, although reception is almost incomparably better using the vehicle's antenna (no surprise). A recent camping trip to the Panoche Pass Hills BLM plot about 2 hours S.E. of the Bay Area put us out of cell-phone reception, but the C.B. had no trouble picking up a nearby NOAA weather transmission loud and clear.