My car club encourages everyone driving in their sponsored road trips to use old-school CB radios to monitor instructions from the lead car, but instead of installing a mounted unit, I’ve purchased the Midland 75-822 handheld CB, and as long as I don’t stray too far from the group, I’m pleased with the performance, using the handheld’s rubber duckie antenna in my convertible. I know the transmit range is limited (especially in a normal vehicle with a steel roof) to around a half-mile using the flexible rubber antenna. I was lead car for a portion of my first trip with this CB, and everyone was able to receive me fine.
Looks like the handheld unit is small enough to fit into the cupholder, so I used sergey’s free 3D-print file to print a bracket designed to be a cellphone mount that inserts into the cupholder slot that I’ve suspended a Rubbermaid Vent Catch-All from, using a 3/4″ long M8 x 20 mm bolt and nut. Using the rechargeable battery pack in conjunction with 8 rechargeable batteries, I’m able to get at least one full day of usage without any cords.
If the antenna proves to be inadequate, I’ll consider purchasing an external mount antenna* that plugs right into the mobile adapter cable (as shown above).
Regarding the installation of a mounted CB radio unit, there really isn’t room to dash-mount a CB radio in these little roadsters, but I had an idea for those considering installing one. Since CD players aren’t installed in the 124 Spiders, the DIN slot dedicated to the player (because they are standard equipment in Miata’s MX-5) might be an ideal location. As an example, shown below is Uniden’s Pro510XL CB with RF Limited’s optional mounting bracket. The “delete CD player” blank panel covering the opening should just pop out. I’ve also read that a “CD prep” harness may even be in that location if you have the Bose system, which would at least give you the power feed, although the amperage capability may be questionable. I also noticed that Cobra makes a CB unit that has Bluetooth capabilities and wonder if it may pair up nicely with the Infotainment system, at least for audio output through the headrest speaker.
⇓ Regarding the antenna installation, Mark Booth has an excellent writeup (photo below is his as well) on modifying the AM/FM radio mast so that it can also serve as the CB antenna. Please note however, that although the modification was easy on previous versions of the Miatas, the job is much more difficult in our 124 Spider, since an antenna disconnect jack is no longer used at the antenna – the wires are soldered directly to the antenna/amplifier module.
* The only horizontal steel surfaces available on the Spider for a magnetic mount antenna are the top of the rear fenders and the narrow panel between the soft-top opening and the trunk lid, but that panel may be too narrow, depending on the diameter of the mount. The trunk lid itself is aluminum, so the magnetic mount won’t work there.