In message , BartC wrote

(In fact, I'm just done a test on a digital TV, disconnecting the RF lead at
a joint: if the outer screen is in contact, I start to get a picture when
the inner core is 2 or 3 mm away from the centre pin! So the signal can jump
an air gap of a tenth of an inch,

But if the coax is also being used to supply power to an amplifier
(unlikely in the case of the OP) the dc voltage will not jump the 2 or
3mm gap.

--
Alan
news2009 {at} admac {dot} myzen {dot} co {dot} uk