Curious... the flightline guys working on F-106 aircraft, to troubleshoot would disconnect the antenna from the ASQ-25 TACAN transmitter ( 1 of 4 boxes) and see if they could draw an arc using a pencil. VSWR went high and the 3CX100A5 finals would often blow and/or arc through the Teflon insulation wrap. I can't tell you how many failures were caused by this troubleshooting technique.... (DAFB early 60's)