Beam Antenna Repair Day – Saturday 18th March 2023
The CCARC’s 20M, 15M and 10M beam antenna at our clubhouse had developed high SWR so we decided to have a working bee to fix it up. We put the word out and got a very good roll up of willing helpers on a clear warm day.
We started the day with a project and safety briefing and split up into different groups including roof crew, safety monitor, ground crew, documenter, VNA crew, photographer / videographer and project manager.
First task was to sweep the antenna with a VNA for a baseline measurement. That done, the antenna was lowered to roof level for access. Dave – our resident qualified rigger did all our roof work using James’s harness and restraint system. First off the Balun was disconnected and passed to the ground crew. Inspection confirmed it was in good condition so we moved on to the next job. One side of each element was removed at a time and passed to the ground crew. All joints and traps were first measured then cleaned and re-assembled before refitting on the antenna. Rinse and repeat for the entire antenna. The antenna was in very good condition except for one badly corroded joint where the balun connects to the driven element. Dis-similar metals caused the corrosion. The feed cable was measured for loss and passed the test. Everything was put back together and joints waterproofed with self-amalgamating tape.
The antenna was winched back up to it’s full height and once again swept with the VNA. A remarkable improvement was noted but it will require some fine tuning on the 15 meter band to get resonance just where we want it though it is usable now.
As luck would have it, an international contest was taking place the following weekend so on-air tests were made confirming the beam’s directivity and performance.
I would like to thank everyone who helped out on the day. Everyone worked safely and efficiently with good humor to get the job done.
Graham VK2GRA
