I am trying to find a suitable connector (PL-259) for 213 cable that will screw
on to the connector at the base of the above aerial. Its a tri-band white stick
about 2 mtrs long.

My connectors seem to screw on about 2 or 3 turns then stiffen up and won't do
up fully, as if its a slightly different thread.

I do seem to recall that there are / were two threads at some time in the past,
but I have only just bought the aerial and connectors, and assumed they would
be the same thread.

Can anyone confirm / answer the problem ?

Thanks,

Nick