Molten plastic for electronics enclosure

Hi, I have a tiny electronic circuit (RF active antenna with fitted SMA connectors) and I want to enclose it in molten plastic or other resign, so that I can create a short of "rubber duck" antenna. The major concern is the SMA connector, which is fitted in molten plastic in commercial rubber duck antennas. This allows the user to screw the antenna to the sma of the transceiver by hilding the antenna body to his hand.

Have you got any ideas of how can I achieve this?

I suppose the main body of the antenna is a pliable substance like silicone sealer? And you want to embed a tiny connector in the end? I picture your problem being at the contact between metal and silicone. It is subject to stress and flexing. The metal will easily break contact from the silicone.

You need more 'grabbing surface'. I think it would work if you were to encase the connector in a larger epoxy shell. The mold might be a soda straw 1/2 inch long. Hold vertical. Fill with epoxy. Dip the connector down into it. Possibly fabricate some kind of protector so that goo does not get on the threads of the connector.

Another idea I had, was to mill a small tube out of plastic, with the internal diameter to be a bit smaller from the SMA connector HEX nut. Then heat a spare sma connector quite hot and press it inside the tube. The heated metal body of the connector will melt the plastic and shape the plastic hole into a hex shape that fits exactly the SMA connector.

It is difficult to fit firmly the connector to the antenna body as you said.