At one time or another most MF and LF operators have had an accident with their antenna systems where fire was involved. As a member of this club, I can say that its never fun when something burns up as it usually happens in a difficult to reach and repair location. Below are images from a few members of this hallowed club. Check back regularly as I expect the offerings to grow over time.
Roger, VK4YB, recently submitted this offering which shows the awesome energy associated with 450-watts of RF power at a high voltage point on one of his end-fed antennas. Note that these antennas are supported at something like 100-foot above the ground so the branch that this wire was adjacent to must have burned up before the wire fell and did this damage.
Laurence, KL7L / WE2XPQ, provided this iconic picture a couple of years ago after a bolt (the one pictured), got too hot after being subjected to 55-amps of RF current at 137 kHz. Laurence repaired the ATU, which has traveled all over the world with him but the bolt had to be replaced.
Larry, W7IUV / WH2XGP, reports that this is what happens when “dirty ice” builds up inside the coil form. He indicates that the first picture is the covered coil while the second image shows the cover removed and the full extent of the damage.
This next offering is mine. It occurred on a very cold January night in 2014. I can only imagine that the cold temperatures stiffened the plastic tubing I was using as an additional layer of protection with my PTFE-insulated high voltage leads off of the coil. The stiff tubing probably was stressed when I moved the variometer after a CW session back to WSPR. So much for extra protection! Fortunately the power supplies for the amplifiers responded to the over-current conditions and stopped the otherwise runaway event.
Neil, W0YSE/7 / WG2XSV, now located in Washington state, reports that “When in Utah, I had an incident happen at the base of my vertical antenna. I was “hot switching” the coax taps at the base of the loading coil and things went sour. I discovered this arc-over on the back side of my PVC “insulation”. I had to re-mount the base on a new PVC pipe to be able to transmit again on 630 meters.”
John, WA3ETD / WG2XKA, submitted this offering of one of his original 630-meter verticals:
“At one point the TX vertical consisted of 35′ telescoping aluminum tubing, coupled to 2x, 100′ top wires on 4′ spreaders. The 2″ bottom section was insulated with a 1/8″ thick black PVC tube, clamped to a piece of 3/4″ pressure treated plywood, which in turn was clamped to an iron steam pipe. The PVC broke down and burned thru to the conductive copper sulphate plywood, as seen. The vertical now serves as my RX only vertical, no HV!”
Ralph, W5JGV / WD2XSH/7, submitted a large number of pictures that I sorted through to find three that I thought were the most dramatic. I suppose the “take home” message here is that PVC insulators will burn when ignited and it will generate chlorine gas that will corrode everything and potentially kill you in a very horrible way if you breath it. Most likely carbon tracking started the process off due to surface contaminants on the PVC. Ralph also reminds us that antennas and loading coils are not the only parts of the RF system that can burn as semiconductors will fail in dramatic fashion with fire, projectiles and noise. All we are missing is scorched earth!
Merv, K9FD/KH6 / WH2XCR, submitted the image below of fire that came thought the PVC base insulator of his low band vertical. Merv explains:
“This is the base of my vertical, about 3 foot of gray electrical PVC conduit makes up the base insulator, 3 inch irrigation pipe makes the vertical… Was tuning and all was fine with low power, but at higher power the SWR kept going berserk. Could not find a problem until I walked around to look at the vertical and there was a huge black carbon trail.
Where you see the “strip” of clean in the black area is where a ground strap was before. Fire jumped through the PVC from the vertical to the ground strap, about 8 inches. I removed the ground strap. PVC is not the best insulator when it at a high voltage point. I changed the tuning circuit and cleaned off as much carbon as possible. Its ok now but needs to be changed at some time.”
I know there are a lot more stories and images! Send them to me for inclusion with your story! MF, LF, VLF – it doesnt matter! Let’s be careful out there!