Small parts, big problems

A bad connector can waste more signal than the whole run of coax, and it’s one of the most common causes of intermittent faults. Getting connectors right is cheap insurance.

The connectors you’ll meet

• PL-259 / SO-239 (“UHF”): the standard on most HF radios and many VHF mobiles. Fine through HF and 2 m; not ideal above that.
• N-type: weatherproof-capable and low-loss at UHF and above. The better choice for outdoor connections and 70 cm.
• BNC: quick bayonet connector for test gear and some handhelds.
• SMA: small threaded connector on most handhelds. Watch out: some radios use SMA-male on the radio and others SMA-female, so antennas aren’t always interchangeable.
• NMO: the standard mobile antenna mount, not strictly a connector, but you’ll see it everywhere.

Choosing coax

Loss rises with frequency and length. At 2 m, over 30 m (100 ft) of cable, roughly:

• RG-58: about 6 dB lost, three-quarters of your power. Only for short jumpers.
• RG-8X: about 4.5 dB. OK for short runs.
• LMR-400 or equivalent: about 1.5 dB. The right choice for longer runs, and essential on 70 cm.

On HF the losses are much lower, so lighter coax is often fine.

Making good connections

• Use the right connector for the cable size, and the right tools.
• Solder or crimp the centre pin properly, and make sure the shield is fully connected.
• Check with an ohmmeter: no short between centre and shield, and continuity end to end.
• Weatherproof every outdoor connection: good tape, then self-amalgamating tape, then more tape. Water in coax ruins it.
• Minimise adapters. Every adapter is one more place for loss and trouble.

Last updated October 2026.