I’m currently looking for a better way of mounting a number of different gadgets to my car, including my iPod, two ham radio remote heads, my Garmin eTrex GPS, and perhaps a few more. Since many of these devices will be upgraded over time, I need any mounting system to be standard enough and interchangeable enough to make this a no-brainer. It appears that there are at least two standard mounting systems that would help me—the AMPS and NEC mounting hole patterns. These are common on many of the mounting brackets on the market, including those from Pro-Fit International, Panavise, and RAM Mounts. Some have both, though the AMPS pattern is more common.

It’s not just these three companies that use AMPS—it is found on some GPS navigation systems (Magellan, at least), many XM radios, and many automotive mobile phone mounts.

Yet despite knowing part of the AMPS specification (a rectangular hole pattern measuring 1.496 by 1.181 inches on-center), I can find no verification or definition of the standard; nothing that comes close to a citable source or reference document. I asked Pro-Fit International’s product designer (co-incidentally a fellow ham) about this, and he knows that it was a Motorola-originated standard, but has never seen a specification either. And there is no agrement on the spacing, either. One drawing from RAM Mount Systems shows 1.50″ × 1.188″ with a hole diameter of 0.218″, and nowhere can I find any mention of what size screw or bolt and thread count is to be used when designing female threads into a device.
AMPS appears to be a long-lived mounting system for the mobile electronics industry, but with no technical documents to reference, its specifications and existence seem to get passed around by word of mouth. This is insane. And it has now become one of the acid tests for CADJournal. If you make a product designed to go in a car—or a CAD tool used to design them—that I wind up reviewing, support for the AMPS pattern (along with other interface standards) will be one of the items I grade on.