Continuity at masthead VHF.

[Clyde Coastin']

Hello all,

I’m having a 3 days from lift in disaster. In my wisdom I have re-wired my mast during the off season, turns out that my new rg8x cable isn’t compatible with the bullet fitting on my VTRONIX mast head antenna.

I kept the last 8 inches or so of the old cable and the plan was to splice the old cable to the new one at the mast head.

The issue I’m having is that when I connect the old cable to the antenna I get continuity between the core and outer of the box of cable. Is this normal?

I was talking to a guy at the yard who went and came back with an old VHF antenna, not VTRONIX but similar design, this time with a pl259 connector.
I then put my meter on this antenna (no cables connected) and again got continuity between the centre pin and the outer threaded parts.

My question is, is this normal? Or are both units knackered? If they are I’ll need to frantically scour local chandlers for a new unit before Saturday.

 

[Martin_J]

A dc resistance measurement isn't a huge amount of use on a VHF antenna that's likely to have a base load (coil) at the bottom.

Some of the V-Tronix marine antennas will for example measure 10kΩ between centre and outer (and this is detailed in their instructions).

Best connect up and maybe borrow a power/SWR meter, although bear in mind that if the antenna is parallel and close to the ground, you might not get the same measurement as if it were in clear space when vertical (but better than teat).

10kΩ could look like short circuit on your meter so maybe about right though.

 

[Martin_J]

An example from Shakespeare...


With spec..

 

[William_H]

Some VHF antenna will have a DC resistance reading outer to inner (even 0 ohms) but some do not. So likely your antenna is OK. As said only comaprison to same sort of antenna or VSWR meter testing will confirm. ol'will