Hello

Hope someone out there can help!
I've just started a private investigator business.
Part of the equipment I use is a recorder/receiver unit (basically a
sony tape machine with a receiver built on to it). The aerial appears
to be a black plastic coated, bendy single wire 16cm long with a small
3mm (approx) screw thread on the end which screws into the receiver.
It appears to be single core, in that, the screw thread is a solid
piece (not like a two piece jack plug for example).

I want to be able to connect an external car ariel to the receiver as
at present the receiver with the aerial screwed in is hidden inside
the car and the reception is very poor.

Some questions:
Is the aerial single core? I naively thought all aerials had a core
and screen.

Could I take a connection from the centre core of an existing wing
mounted car aerial and run a single wire to the receiver inside the
car?

If I used this method would the external car aerial have to be 16cm,
same as the plastic aerial?

Can these small 3mm screw threads on the end of the existing aerial be
bought from somewhere so I could connect my external aerial to the
receiver?

I hope this all makes sense and I would be very grateful for any
advice.

Thank you