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  Three coax cables, one hole in the shed wall, and a connector that definitely looked smaller before you fitted it. That’s usually when sharing a feedline starts to sound sensible. A triplexer can put three separate frequency ranges onto one coax cable, while a diplexer handles two. For a station running HF, meaning high frequency, alongside VHF (very high frequency) and UHF (ultra high frequency), that can save a fair bit of cable. It can also make a mast installation easier to manage. Fewer cables to support. Less wrestling at the wall entry. There’s a catch, naturally. The filters have to suit the actual frequencies, and the boxes need to go in the right places. You’ll also need to account for signal loss and check what happens if one radio transmits while another is listening. We’ll work through those decisions here, including the difference between a band splitter and the duplexer used on a repeater. The installation scenes below are illustrative examples, rather than accoun...

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...

  I’ll never forget the weekend I spent tearing my station apart, thinking my new HF transceiver was the culprit behind a mysterious noise problem. I had installed it a few weeks earlier, and everything seemed fine at first. Then, during a late-evening net on 40 metres, there it was—a faint, buzzing hum creeping into my receive audio. It was subtle but maddening. I swapped coax, retightened connectors, even fiddled with grounding schemes, but nothing worked. Then I remembered a conversation with a fellow club member about Diplexer use in multi-band setups. Honestly, I almost dismissed it as overkill—but that lesson cost me an entire weekend. Where Things Started Going Wrong I had a classic setup: a 20-year-old HF Yagi for 10–20 metres, a vertical for 40 metres, and a mobile whip for 80 metres. Each antenna had its own feedline, and I was hopping between them depending on propagation. What I didn’t account for was how signals from one band could bleed into another through the feed...