Adding a BNC Socket to a PMR446 Radio

This page shows how a PMR446 walkie-talkie was modified to use a BNC coaxial connector rather than the built in antenna. The radio is a Binatone MR180.

Mods to front part of case.

The socket to be fitted is a chassis mount BNC. The screw thread on the socket is a neat fit in the hole in the case where the radio's fixed antenna is fitted. There is an anti-rotate lug in each half of the

case. On the front part, the lug is removed completely, and some clearance is filed into the top edge of the PCB to make room for the retaining nut that comes with the BNC socket.

Mods to rear part of case.

Here, the lug is kept but is filed down to reduce its height - want to keep some so that it bears against an anti-rotate flat in the threaded part of the BNC socket. The pillar around the screw hole in the case fouls the centre pin on the socket, so some material was removed from one side to allow the pin to come into the case in a straight line.

The socket fitted to the radio.

The socket has been fitted to the radio. The anti-rotate flat on the socket's thread is clearly shown. Note that the insulator in the socket has been cut back until it's flush with the metal body, to stop it fouling the PCB and the support pillar in the other half of the case.

The round collar at the end of the socket's thread, with the orange wire routed to it, was originally the retaining nut for the chassis mount socket. There was no space for the the unmodified nut, so the flats were machined off to to create a smaller, rounded collar with an internal thread. The orange wire is soldered to the collar and is led to a ground, and very short piece of stripped wire is soldered to the centre pin and formed into a small loop which connects with a pad on the PCB (the loop is trapped under the screw hole pillar in the back half of the case).

Comparison of unmodified set and socketed version.

An unmodified set beside the BNC version. The black object above is the antenna from the modified set. It's a small helicoil of wire inside a bendy plastic tube.

Replacement antenna.

The replacement antenna consists of a BNC->Phono adapter, a length of coiled wire and the plastic case from the original antenna. The wire is stripped at one end, formed into a couple of loops, and jammed into the phono socket. The bendy plastic tube is a nice push-fit over the phono socket.

Before and after with new antenna mounted.

Here are the two radios, unmodified on the left, and the BNC version fitted with the home-brew antenna.