Once payment is received antenna splitters are customarily mailed from the local post office twice or more per week.
I've been making Miata special antenna splitters for those on Miatafun.net and Miata.net for more than ten years. I personally make them using more than 40 years of professional electronics engineering experience in radio communications and antenna designs. I can only make them as I can find time. When I don't have immediate availability I keep a waiting list to notify you when I have one available for your Miata. I attempt to maintain immediate availability, or if not, I can usually get one built for you within 30 days of your confirmed request.
All models are supplied with detailed instructions with drawings. The cable to the CB is approximately 10 feet long with a standard CB screw-in coaxial connector (PL-259). A BNC connector (type used with some CB walkie-talkies) is sometimes available by request, or an adapter can be used, Radio Shack, #278-120.
These Miata antenna splitters are special made and performance optimized for easy plug-in installation in the Miata's trunk. They can be left installed in the car with no noticeable effect on AM/FM radio reception. They are not suitable for use with another type antenna -- THEY ARE ONLY FOR THE MIATA'S FACTORY ANTENNAS. Because of this they provide high-performance equal to or better than many commonly used types of magnetically mounted CB antennas, and do not noticeably degrade reception of AM or FM. They are built for the CB radio's 4-watt legal power limit to provide long life and very dependable operation in a nicely constructed sheet metal box approximately 2-7/8" X 1-11/16" X 13/16" inches.
They are made and preset for each specific Miata antenna type; however, due to variances in the Miata antenna from one sample to another, they may require resetting to precisely best match the antenna on your specific Miata. Without resetting, the preset user adjustment provides quite effective performance. They can best be set with a SWR meter. Instructions are provided to enable setting the splitter without using a SWR meter by just listening for maximum CB reception. SWR at band edges is less than 3:1 and typically around 1.1:1 at best-set center band CB channel.
For pre-2006's the antenna splitter's cable to the CB radio can be run directly into the car by simply folding the vertical carpet down behind a seat (for 1999 - 2005's temporarily unfastening some of the trunk's interior trim may make running the cable easier). The upper outside corner of the carpet is held in place by Velcro. Once the carpet is pulled down a hole into the trunk is exposed. The area behind the Velcro-held carpet makes a nice pocket for storing the CB cable when it's not being used. For 2006's and later, interior panels must be temporarily removed.