Busted, more Garmin smarts
OK, it wasn’t the smartest move, me trying to jam the cable back into a very funky old external antenna while the Garmin 545s it was attached to was still running. Apparently I shorted the cable because, surprise, the Garmin beeped and told me so! I can’t say that I’ve tried this on any other GPS, but doubt I’d get such an informative reaction. One more check on the smart interface list.
Garmin’s had this for a while, my 192c had the same error when I twisted my antenna too far.