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 although the performance with the rubber duckie antenna is OK if the other vehicles are in close proximity (within ¼ to ½ mile), I determined that if I wanted to serve as sweep or lead, I needed a real antenna*. I first ordered a Cobra CBRHGA 1500 magnetic-mount 36″ antenna, but aside from it arriving bent, I determined that the quality was sub par, especially the most important piece, the rubber insulator that protects the base and magnet from damaging your paint. The rubber was WAY to thin! So it went back and I ordered the Tram 300 Magnetic-Mount CB Antenna Kit, which is also 36″ and is a perfect solution. A very nice wrap-around rubber boot that is thick enough to insure no damage to your paint! I can vouch that the magnet holds firm at 80 mph+ 🙂 and what a difference in the radio performance!
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, however if you are using the external antenna, you can not use the battery pack and you must instead plug the power cord of the mobile adapter into the 12-volt outlet in the passenger’s footwell.
* The only horizontal steel surfaces available on the Spider for a magnetic mount antenna are the top of each rear fender (which actually work nicely, unlike the MX-5 rear fenders, which has no flat horizontal surface) and the narrow panel between the soft-top opening and the trunk lid, but that is narrower than the 3″ magnetic base (may not be sufficient hold for high speeds and you’d have to move it before opening the trunk lid). The trunk lid itself is aluminum, so the magnetic mount won’t work there. If you are using an external antenna, keep in mind that you must use the mobile adapter (shown on the left side of the top photo, rather than a battery pack.
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.