Mr. Carlson Gets Zapped By Snow

As a Canadian, [Mr. Carlson] knows a thing or two about extreme winter weather. Chances are good, though, that he never thought he’d get zapped with high voltage generated by falling snow.

[Mr. Carlson]’s shocking tale began with a quiet evening in his jam-packed lab as a snowstorm raged outside. He heard a rhythmic clicking coming from the speakers of his computer, even with the power off. Other speakers in the lab were getting into the act, as was an old radio receiver he had on the bench. The radio, which was connected to an outdoor antenna by a piece of coax, was arcing from a coil to the chassis in the front end of the radio. The voltage was enough to create arcs a couple of millimeters long and bright blue-white, with enough current to give [Mr. Carlson] a good bite when he touched the coax. The discharges were also sufficient to destroy an LED light bulb in a lamp that was powered off but whose power cord was unlucky enough to cross the antenna feedline.

Strangely, the coil from which the arc sprang formed a 36-ohm shunt to the radio’s chassis, giving the current an apparently easy path to ground. But it somehow found a way around that, and still managed to do no damage to the sturdy old radio in the process. [Mr. Carlson] doesn’t offer much speculation as to the cause of the phenomenon, but the triboelectric effect seems a likely suspect. Whatever it is, he has set a trap for it, to capture better footage and take measurements should it happen again. And since it’s the Great White North, chances are good we’ll see a follow-up sometime soon.

Thanks to [Käpt’n Blaubär] for the tip.

45 thoughts on “Mr. Carlson Gets Zapped By Snow

  1. I’ve seen some electrostatics with colder than 15C dry snow before, like getting a good shock off your car after driving in it. Or it flying back to the plastic shovel when you’re trying to dump it. Only really cold powder or small pellet stuff though. I believe that it can be at a few kilovolts in the cloud, before it drops also, so don’t know if it can bring that charge down with it, if say you had an ungrounded tin roof, and build up potential on that, without local wind action.

    1. What? You folks have never heard thunder during a snowstorm? It’s pretty well-known that precipitation can cause lightning, or extremely large charges that do not result in a stroke of lightning but bleed off to ground in a way that will cause the clicks heard. Even if it’s snow rather than rain.

      For this reason hams are taught to ground the coax using a lightning arrestor at the tower base (if there’s a tower), and where it enters the home. This directly grounds the shield, and grounds the center conductor through a device that should conduct once a certain voltage is exceeded.

      It’s also prudent to disconnect your antenna during a storm, especially if you do not have protection devices but even if you do. And if you see things shooting sparks, get away from there is the first thing you should do, rather than grabbing the antenna wire.

        1. I was surprised during a blizzard in the early 1990’s.
          I was driving at night to work at the weather center in Colorado.
          The snow was getting deep so I pulled off to the side and put on tire chains.
          While I was doing so, I heard thunder a number of times ( a bit muffled by all the snow) and the lightning helped me see what I was doing.
          When I got to the weather center, I asked the scientist who was the Principle Investigator, if it was really thunder and lightning I was experiencing.
          He confirmed that I was.

        2. I can’t say I saw a lightening bolt because the snow was too heavy to see further than a few meters but it did light up the sky and the thunder followed shortly after. Other hams on the skywarn net that night reported it as well. Of course, you may not know me ;-)

        3. I actually did despite being younger then you and living in Central Europe, which does not have any extreme winter weather…though it took me a while to realize WTF was going on…

        4. Beg to differ. Here in the UK, a few years back, we had a sudden episode of about a week of snow (heavy, for us!), termed “The beast from the east”, as it was quite a lump all in one go and there was definitely a thunderstorm where I live in the middle of a heavy snowfall one evening. No question.

      1. I have heard and seen thunder snow here in North Carolina a few times in recent years and back when I lived in Florida I used a old automobile spark plug as arc protection in my 70’s ham shack. But it is always best to disconnect your sensitive equipment from the antenna when not in use.

  2. > the coil from which the arc sprang formed a 36-ohm shunt to the radio’s chassis, giving the current an apparently easy path to ground.

    Bare in mind that you are not dealing with DC here. The snow flake is similar to the ESD model. i.e. a small capacitor charged up at a very high voltage. The discharge event has a very narrow high voltage pulse. i.e. a high frequency content. It will find a path with lowest *impedance* and that might not necessarily have the lowest DC resistance.

    Sooner or later, you’ll have to unlock your skill level by starting to think about AC models of everything you come across.

  3. A pulse of voltage can go thru a cap, that’s how they work. The impedance of the coil is much higher than 36ohm. You can have hundreds of volts across a loaded antenna transmitter coil, this always mentioned in the ARRL handbook. No mention and a doubt that he has a lightening arrester in that longline antenna. Yikes! A near strike would conk your lab, direct hit fire and smoke. Insurance issues! Ground the other side of that coax it’s not a second antenna. This will of course mess with the tuned input. A longline for such a mediocre 2 stage AM radio, go for a tuned loop antenna. Good car radios do a great job at AM and FM. The latest FM’s go from 50 usable to 100 channels of usable reception. AM is getting as historical as that radio.

    1. Yep that’s most likely. While capacitor leakage was measured, what is the capacitor breakdown voltage e.g. measure with a megger. If we knew the coil indictance then could see what pulse width is involved. By the arc length is a few kV.

    2. Came here to say the same. I’ve seen this in my lab when there’s HV present (for charged particle work). Mr Carlson seems to think ohms are more important than henries, and not understand what’s going on here.

      The antenna itself is a capacitor to ground, usually a pretty high Q one. It picks up some DC, which eventually is enough for the little capacitor in the radio to arc over internally, discharging the antenna parasitic capacity into the choke to ground, which has high reactance for fast events – might as well not even be there – other than to initially allow the coupling cap to charge up.

      Once you have arcing around a bunch of tuned circuits, you can get voltage stepup, you have large pulsed magnetic fields coupling into other things “accidental transformer-wise”, and so on.

      One thing I often have to remind students of is that there’s a lot of reality that isn’t explicit on a schematic – parasitics really matter!

      The power lines are not that simple, for example, having inductance and capacity along with the resistance anything not a superconductor has – and you can’t necessarily treat those as lumped constants.

      I went through a fair amount of trouble to prevent (further) destruction of solid state stuff used as instrumentation and data aq in my lab where some of the same sorts of things tend to happen (there’s a high power 50kv source… and a tiny C discharging can make 100,000 amp pulses in what is a one turn coil – it’s difficult to shield against that kind of EMI).

      I will say that pro grade test equipment can handle a lot of this easily – he’s going on about utter destruction, but maybe doesn’t have as much experience with the more modern stuff. Tube stuff, of course, is pretty hard to make poof.

  4. One time, December 1960, Carl & Jerry tried to make snow, using a big ultrasonic generator. And there was snow, they worried they’d got carried away. But the ending was unclear whether they were the cause, or if it was chance. This was in Popular Electronics

  5. Nothing new. Every shortwave HAM knows. In the all my six decade experience, the longest sparks prom LW antenna, produced by an overfrozen snow I ever seen were about 3 cm! Solution is easy – the RF choke from antenna to the ground. Because a very low current, an quarter millimeter wire is good enough, the higher inductance of the choke the better. Ferrites welcome.

    The best solution? Good grounding switch:

    https://i.warosu.org/data/diy/img/0016/72/1567242722549.jpg

    1. The radio was plugged into an isolation transformer… so chassis was deliberately floating.

      That said, the effect it had on the LED lamp makes me wonder if it didn’t find a route to the neutral line via its line cord which was apparently in close proximity to the radio’s own line cord.

      i.e. it wasn’t as isolated as originally thought.

      1. The antenna coil is referenced to terrestrial earth.

        Heaters are often referenced to chassis or earth through a center tap of the transformer secondary.

        I can see one valve in the pic that has an anode voltage between 400 and 600 volts. This is much higher than the insulation breakdown voltage of the mains cable.

        If you have isolated earth then the breakdown voltages of capacitors is probably lifting the chassis or earth reference.

        The arc your seeing is probably only half the issue. The other half is probably in a cap or valve.

        The schematic will answer this question and also show how to best isolate this.

        Post the schematic here if you can.

  6. Perhaps there was another accidental spark gap in the electrical chain allowing the buildup of voltage. Somewhat like a Marx generator, your radio might have just been the last spark gap so there wasn’t enough time for the charge to dissipate through the low resistance before an arc formed. Even more so if whatever the resistive path to ground had a significant amount of inductance.

  7. I subscribe to Mr Carlson’s Lab on YT and always great info on troubleshooting but this recent post was unexpected yet very believable. Dry/cold snow, volcanic ash, dust storms and I have been shocked a few times from a glass bead blaster a time or two. But this arching went on for quite a while……

  8. The “Isolation” transformer insulation may now be compromised too.

    Not strange at all.

    You’ve just been introduced to the EMP effect, caused by very fast rise (or in this case, fall)time electrical fields.

    The DC resistance of the coil to the chassis, is not the important factor. But the inductance of that coil is. My guess is, that when the voltage built up to arc over in the isolation transformer (or to your LED lamp) there was enough of a voltage step and fast enough for the coil to show as a very high resistance (impedance) resulting in a large enough voltage across it to arc to the local chassis.

    In future, best to have a high value (3M Ohm) from both coax inner and outer to real ground, to drain any “environmental” static away, before damage is done.

    Oh, take care with the old Tek’ scopes, they have semiconductors in too, even the delicate unobtanium tunnel diodes some use in the trigger circuits.

    73

  9. bit of an old man moment at the end going on about his WW2 era oscope, like that’s great gramps … some of us need to measure more than a few megacycles while we test our “electronic brain”

    1. How about a bit of respect for the old farts that actually know something? According to the web the tunnel diode was invented circa 1957. So no “WW2 era oscope” used one.

      Do you even know what a tunnel diode is? Have you ever used one? And yes, you can still buy one, but I recommend not picking up a counterfeit from ebay or any number of Chinese sources.

      After working more than 40 years in the electronics industry, I still respect the knowledge and experience of the old guard. Listen to them, like I have, and you might learn something too.

      The few responses that mentioned the impedance/inductance, not the resistance of the coil in the OP are dead on. Fundamentals, kids. Listen to “gramps”; he’s already forgotten more than you have ever learned.

      There is a lot to be said for old band-width limited equipment, too. But it is a lot more important to understand the fundamentals of electronics than to have a fast “oscope”.

      A little respect, kid, would serve you well.

  10. The mystery isn’t so much how the electrostatic charge formed, but why a coil with only 36 ohms resistance didn’t short it to ground. As Mr. Carlson briefly mentions, high power RF picked up by his antenna would do that but he was unable to tune the circuit with the variable capacitor to see if RF was involved because he didn’t want to touch it.

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