Tacile Feedback?

I'm in the midst of working on my transponder install. I've got three
antenna cables running to the radio/transponder panel. Two are for the
Narco Nav/Comm and attach via BNC, the other used to be soldered to the
rack for the old transponder but will now get a BNC fitting as well.

Accidentally swapping the Nav/Comm antenna connectors made little
difference to the radio performance, but now the transponder cable will be
added to the mix and attaching the wrong cable to a device would be bad.

I'll add the appropriate labels to the ends of the cables, but most of the
time, I end up attaching the BNCs by feel. I was wondering if anyone had a
good suggestion for changing the tactile characteristics of the transponder
antenna cable.

In other words, when I reach back and grab the end, I'm going to want to
instantly know it's the transponder cable without being able to read the
label. Any suggestions?

Ron Wanttaja