comtekradio

  A bloke once walked in with a perfectly good dual-band radio, a new length of coax and three adaptors screwed together like a little brass sculpture. None of it was doing quite what he expected. The antenna had an N-type socket, the radio wanted a PL-259, and somewhere along the way he'd added a BNC adaptor because it looked close enough in the online photo. It fitted. Sort of. The receive side sounded weak, his SWR reading wandered, and touching the adaptor stack changed the result. Naturally, the radio got blamed first. Most people don't think much about coaxial connectors until the signal drops out. They're small, inexpensive compared with the radio, and often bought at the end of a project when patience and budget are both running low. Yet that little joint between the radio antenna cable and the equipment has to preserve the shield, maintain solid centre-conductor contact and carry RF without introducing an ugly impedance change. It also has to survive movement, vib...

The first time I tried running two radios through one feedline, I treated the problem as though it were plumbing. One line coming down from the antenna, two radios sitting on the bench. Surely all I needed was a fitting with one connection on one side and two on the other? Simple. It wasn’t. I found an old television-style splitter in a box, added enough adapters to make the whole arrangement look vaguely professional and connected everything. Reception was poor, the readings didn’t make much sense, and transmitting on one radio made the other behave as though someone had thrown a wet blanket over it. Nothing actually smoked, thankfully. It could have. Look, I’ll be honest… at that point I didn’t properly understand what an antenna diplexer did. I’d heard the term, but in my head it was mixed up with splitters, antenna switches and several other little metal boxes that all seemed to have one connector too many. That afternoon sorted out the confusion rather quickly. What an Antenna D...