Was working on a Collins Rockwell 100w UHF transceiver and keep having weird readings on the Bird wattmeter. Went to change the wattmeter element and felt what felt like a small shock on my thumb and index finger. Adjusted the element and keyed the radio again. Again weird reading. Adjust the element again, small shock again. Looked at my fingers and voila, small blisters. Stopped using myself as an experiment and started looking at my test equipment. Turned out that the RG-323 cable I was using had a bad shield and was causing there to not be a good ground….. until I touched the wattmeter creating the ground. Learned a valuable lesson that day, sometime when something looks weird, it isn’t the equipment with the fault….It is the test equipment.
When I was a teenager back in the early 60’s, we had a Ham Radio guy living next door to us and I want to learn about how to become a Ham.
I would visit him and he had a coax running out of his garage door and he was sending out a CQ when I came in and I put my hand on the coax and found myself back outside wondering what hit me, and now I do not touch any transmission line under power.
Larry – N7LUF
Not me, but when I worked at a satellite Earth Station we were cautioned about testing HPAs Klystrons and TWT (travelling wave tubes) with loads properly connected. Another engineer there had a repaired 14Ghz unit setup to test and had not connected a load to the output. He mistakenly believed that without an input there could be no output whilst he was checking it. The input was also unterminated and was open to pick up noise which the unit then amplified and output at the unterminated waveguide output. This caused a feedback loop and the output increased to a high level. The output was right next to his thigh and he soon became aware of a painful sensation. He was checked out at a local hospital and fortunately microwaving his leg resulted in no permanent damage.
I met a technician when I was in the broadcast industry who had one finger literally “toasted” while he was turning a rotary switch to read the current on the antenna phase meter of an AM station. He was wearing a ring that contacted the adjacent cooper tubing on the meter board… A lot of kw’s went through his hand, for a few seconds, leaving a good burn.
Not much of a burn, but in a horrible place. Probably under 100W into a really crappy antenna with no good ground. The D-104 (Lollypop) mike bit me on the lip. You could barely see the burn, but it hurt a lot for a week!
Working with RF there are two types of people. Those that have received RF burns and those that will receive RF burns. The trick is to survive them.
Back in 2008, I constructed a 5 kW AM station from the ground up, except for the towers and the transmitter. About a year later, on a hot summer day, I was weed eating inside the fence around the high-power day tower. I was working under the feedline from the ATU to the tower. I turned and brushed up against the feed line. Even though I was wearing a shirt, it was sweat soaked. I got a nasty burn on my left nipple.
I’d a truly good introduction into the dangers of reasonable power RF. I’d recently ended my High School education years, left home & was employed as a Tech Trainee in a State run radio station, 18yrs old. I was following my obsession with electronics & this was the beginning of my career. I was soon rostered to shifts but supervised. Then came my 1st maintenance night at the AM transmitter site for the Station. My aged trainer was an engineer who was so familiar with everything he rattled off what we would do around 00:30H. There were three 10kW AM Transmitters that would each be closed down, coupled into a dummy load & restarted whereupon we would run a set of tests & do a response check. The was a smaller 100W standby that had to be brought up after being set frequency-wise to cover the TXr that was closed for maintenance.
So he showed me how i needed to use the wooden ladder & climb the rear of the cabinet to reach the antenna feeder coupling ontop the cabinet undo & move the link to join into the Load after he had de-energized the TXr.
So we preset the 100W to standby, he told me there’d be a loud bang as multiple breakers activated & to do the change-over & after we would put the 100W OnAir. So i waited at the rear of cabinet, he bellowed “CONTACT” and BANG … (that came from what sounded like the other cabinet) but i reached out an did what i had been instructed to do… Instantly little lightning arcs hit my fingers as used spanner to under the coupling link & turned it to join to open frame wirewound load which burst almost white hot for an instant then dimmed to a glowing red… My supervisor yelled “what’s happened”? & the a bit of disbelief… “WHAT THE HELL”? My hand felt warm & my elbow but smelt terrible like burned chicken! Climbed off the ladder & walked to the cabinet front to see my sup studying the panel meters…He was really not happy… “Oh hell no we turned off the wrong TX”.
I had disconnected a 10kW AM TX operating perfectly at full power from no load into a dummy load… I simply did not know what was going on but next thing the poor machine cannibalized itself before our eyes. The large air blast finals went red hot & blew their plates while large disc ceramic caps exploded & inside with material ricocheting inside. Eventually the two halves of the cabinets were opened & the sup said oh no the Mod Tranny… It was boiling with molten pitch spurting out the gasket plate at the top… !!!
A week later my fingers were not good… the internal burns were sore they said but they will come right but you will have scars that could be a problem…
I’m 65 now & i still have some gnarly scars from that experience. Worse, not a lot was ever said about it at all. We tried to repair the TXr (there were parts) but it was too far gone. The 100W sort of covered for a while & eventually a whole new TX was installed..
I ended up more on Studio Duties & never did a maintenance shift at the transmitter site strangely! The training courses i attended to become qualified as a Radio Tech where interesting in that i learned all about transmitters & that they never like working without a Load….