Foundations of Amateur Radio

The other day I was woken by the sound of a thunderclap. It was shockingly loud and came out of the blue. A few moments later, it happened again. I exploded out of bed, rushed to the shack, disconnected the beacon power and switched the antenna coax to "safe".

After breathing a sigh of relief, everything went dark and with it came the distinctive sound of the sudden death of the uninterrupted power supply taking with it my workstation.

With nothing else left to do, I reported the outage to the power company, went back to bed, pulled the covers over my head, snuggled in and surprisingly, slept pretty well despite the barrage of water hitting my QTH. The next morning the power was back on and I discovered that one of the residual current devices, the one that powered most, if not all, the wall sockets had tripped. I reset it and much to my surprise, most of my QTH came back to life.

I say most, because after breakfast I had a moment to switch on my radios and see what, if any, damage there was. I could hear and trigger the local repeater, but HF was strangely dead. I could hear the coax switches turning on and off, but the SWR on the antenna was high and it didn't appear that the antenna coupler was doing anything. It's powered remotely using a device called a Bias-T. You use two of them to transport a power supply voltage along your antenna coax. In my case, I inject 12 Volts in my shack, and extract the 12 Volts at the other end near the antenna where it powers the antenna coupler.

Occasionally the antenna coupler needs a reset, so I removed the power, waited a bit and reconnected. Still no response from the coupler, so I disconnected the power and left it for another time.

A few days later I had a moment to investigate further, so I went outside to check out the antenna and coupler. Both looked fine. I removed and reinserted the power, heard a click, but wasn't sure since a car came barrelling down the road at the same time, so tried again and heard nothing.

At this point I decided that this warranted a full investigation and started putting together a mental list of things I'd need. I wanted to test the coupler when it was isolated, I wanted to do a time-domain-reflectometry, or TDR test, to see if anything had changed. This test uses the RF reflection of a cable to determine its overall length and any faults like a cable break, high or low resistance and any joints. If you have a Nano VNA or an antenna analyser, you can do this test. It did occur to me that I didn't have a baseline to compare with, so that was disappointing, but I added it to the list.

First thing to test was to check if the radio had been affected. I turned it on, did the same tests and discovered that the Bias-T was still disconnected, which could explain why I didn't hear a click when I tested a second time. Armed with a level of confidence around power, I tried again to trigger the antenna coupler and got nothing, dread building over the potential loss of a radio in the storm, I set about swapping my HF antenna to another radio.

At this point I was reminded of an incident, 37 years ago, as a high school student during a class outing. My wonderful and inspirational physics teacher, Bart Vrijdaghs, took us to the local University where the head of the Physics Department of the University of Leiden gave us a tour of their facilities. He took us into a student lab full of oscilloscopes and tone generators and set-up a demonstration to show us how you could generate Lissajous figures. He was having some trouble making it work and with the impertinence reserved for teenagers I quoted a then popular IBM advertisement from 1985, "Of Je Stopt de Stekker Er In", which loosely translates to asking if he had plugged it in.

I can tell you, if looks could kill, I wouldn't be telling this story.

Suffice to say, it wasn't. Plugged in, that is.

Back to my HF antenna.

Yeah. It was already plugged into the other radio, so, unsurprisingly it was unable to send any RF to, or from, the first radio, much like some of the advanced telepathic printers I've had the pleasure of fixing during my help desk days a quarter of a century ago.

After all that, I can tell you that HF seems to work as expected. The beacon is back online and I have some work ahead of me to create some baseline TDR plots and perhaps a check-in, check-out board to keep track of what's plugged in where.

That and looking for another UPS, since keeping the computer it's connected to up and running, at least long enough to properly shut down, would be good.

What other lessons can you take away from lightning hitting nearby?

I'm Onno VK6FLAB