The signal from the Baofeng UV-5R HT tucked behind the seat of my Tour Easy became exceedingly choppy on recent rides. Here’s an earlier version to give you an idea of the situation:
Of course, it worked perfectly in the garage and only failed while on a ride. The clue turned out to be having it fail more on rough roads and crappy scab patches (courtesy of NSYDOT) than on relatively smooth asphalt.
That led me to wiggle of All The Cables while crouched beside the bike in the garage, listening to another HT, and watching the transmit LED. After about five minutes of this, I found wiggling the 3.5 mm connector between the cable from the PTT button on the handlebar and the radio blinked the transmit LED: ah-HA!
The connector had worked itself loose from the straps holding the radio pack in place, pulled some slack in the cable, and was bouncing around in mid-air. A wrap of duct tape now holds the connector halves together, the upper loop passes around the Velco-ish strap, and the lower loop (from the PTT button) goes through the bottom of the repurposed bottle holder:
No trouble on the next two rides, so we’ll call it fixed.
Protip: it’s always the connector.
The Smell of Molten Projects in the Morning 
My experience: it’s the conn3ector first, the cable second.
And why, or why, do people insist on using solid-center-conductor
coax on vehicle antenna installs? Especially on trunk lids?
Mike WA6ILQ
Because SWR! [mumble mumble mumble]