What happens when you touch a pickle to an AM radio tower
jeffgeerling.com
jeffgeerling.com
1. On AM the radio energy literally pulses (the amplitude modulation) and thus the arcs of plasma will pulse too thus creating the audio noise. AM has a carrier wave that’s constant but the two sidebands of signal pulse from zero energy at silence to more power the louder the sound being transmitted. FM signals broadcast essentially the same power all the time since it’s the frequency and not the amplitude that’s changing.
2. Because the signal frequency is much lower on the AM broadcast bands the wavelength is much larger and thus the antennas are much bigger. On AM the tower itself is typically the antenna vs FM radio where the antenna is typically only a meter or two long at the top of a very tall tower. That’s what makes AM towers more dangerous as the tower can be carrying many kW of energy and if you touch it you’ll go zap zap. The towers typically sit on top of a ceramic insulator to insulate them from the ground whereas FM towers typically just are attached right to the ground (although with grounding straps for lightning protection).
Finally (some folks don’t always know this) you can operate AM on the frequencies typically used for FM… it’s just a mode and works on any frequency. Aviation radios operate on AM but in the VHF band near FM broadcast frequencies.
When they put the pickle/hotdog/whatever an inch away from the tower without actually touching it, it doesn't even get warm. This isn't RF, it's just standard-issue AC electrocution. Maybe the one "radio" thing here is that the ground underneath a tower like this is essentially a big metal mesh, but even that isn't a factor -- they're literally hooking a jumper cable from the pickle to ground.
Do you mean burning via resistive heat dissipation from current flow through flesh? There are also burns from plasma in arc discharge events. An arc discharge to the body can produce both.
It would be interesting to see the difference grounding a hot dog through 7 kW AC (60 Hz) and seeing any difference in internal heating and arcing. Maybe a topic to explore in another video—especially if I can get access to a transmitter manufacturer's testing lab...
No outward signs of injury, I just felt an internal burning sensation and severe nausea pretty quickly. I was feeling okay after about a day or two. I never did get checked out by medical, so no clue of what permanent damage was done.
Amperage on a 6kW tower will still be more than enough to kill you.
Imagine only having telegraphs and morse code and amateurs listening every night to the spark noises in morse then suddenly in 1906 (first done in 1900 !) you hear voices and music!
https://en.m.wikipedia.org/wiki/Reginald_Fessenden
can't seem to direct link the photos but scroll down to see what you are talking about with the base of the tower being a massive insulator
scroll to: Brant Rock, Massachusetts, facility
https://en.m.wikipedia.org/wiki/Reginald_Fessenden#Rotary-sp...
Fessenden is famous for developing a electomechanical RF generator which put out a clean sinewave (eg a coherent wave), which helped replace the earlier Spark-Gap systems (which generated wide-band hash).
Two transmissions will produce a heterodyne (whine) due to the offset of carrier frequencies, so you hear both and the tone to know there are two transmitters. On FM, you’d hear only one, the strongest who captured your receiver.
Today we would build these systems with FM or digital voice.
But there are enough advantages we've gotten used to (graceful degradation, better handling of doubling, etc...) that it's not really unequivocally a win to switch to FM. There would be downsides that anger existing users, and it would be expensive, and the net benefit would be relatively small.
This one mostly. As otherwise mentioned, there is some advantage in the case of multiple transmissions at once for AM, but in practice both are often entirely garbled. The loud tone caused by any slight difference in transmit frequencies is the big indicator that something has gone wrong. If one signal is much stronger than the other then that tone will be very faint and will likely be missed. So AM has something like FM capture effect in that case.
AM has allowed for very narrow channels on the aviation band. In Europe mostly, the channels are only 8.33 kHz apart. Typical narrow band FM voice communication requires 12.5 kHz.
Since the end points in aviation are usually within line of sight of one another, radio communication is very easy. Any modulation method would work well. Of course in practice this means that the equipment is allowed to degrade that much more before anyone gets around to fixing it...
It would be a nice thing to do from several angles I think and would help drive interest in radio as a technology in general; as well as building transmitters and aerial systems, there's things like setting up an audio processing chain to get the best possible modulation and being a disc jockey which will always have a bit of a buzz from being on the 'real' radio. If valves and vintage equipment are involved it would be an interesting form of technology history preservation and 'living history', and there's also an environmental angle where old analogue radio receivers could be prevented from becoming e-waste.
There could be a minimal licencing regime to demonstrate the individual is not a complete numpty and a fee to PRS for music rights along the lines of how streaming works. Maximum power could be kept low especially at night to avoid interfering with countries in Europe where AM radio is still an active platform, and I don't think there'd need to be a lot of enforcement with respect to content since you'd only realistically be broadcasting to other anoraks. Additionally there's already precedent for non-profit stations where the medium of AM itself plays a role, for example former pirate Radio Caroline which uses it to keep its historic radio ship in operation.
> There could be a minimal licencing regime to demonstrate the individual is not a complete numpty [..]
I wouldn't bother and it just adds more resistance.
> [..] and a fee to PRS for music rights along the lines of how streaming works.
I think the quality is so low and the audience so few that it wouldn't matter.
> Maximum power could be kept low especially at night to avoid interfering with countries in Europe where AM radio is still an active platform, [..]
Yeah, not sure where the sweet zone would be though.
> [..] and I don't think there'd need to be a lot of enforcement with respect to content since you'd only realistically be broadcasting to other anoraks.
That would be the point, just low-power decentralised communities. Only real reason to get involved is if the power goes too high or band use is not respectful to other users.
It doesn't sound like the sort of thing Ofcom would go for as I suspect it'd be seen as making unnecessary work for them, but you never know. Someone there clearly likes Radio Caroline (despite Ofcom's predecessors having fought to close it for decades in its pirate days) because they got awarded a 1 kW and later 4 kW power limit when AM community stations are usually much lower, so there might be sympathy towards the idea of more community AM generally. It would be a difficult thing to lobby for politically I think because it's such a niche interest, but it'd be an easy thing for them to do and there's not much else that part of the spectrum can be used for easily.
The ham radio licensing process is not onerous.
It would probably be easiest to regulate the transmitters than the people using them.
Not much in there that would stop you from electrocuting yourself, though, I agree.
Licensing the transmitters is the FCC's other standard approach and would probably work except for radiated power safety and antenna issues -- which can be pretty big. You could easily create significant interference or hazard from a botched antenna or connection. (But also which you don't learn enough from just passing the exam.)
It seems like it needs more thought, but I still like the idea of de-centralised community AM transmitters operating.
I agree. My US thoughts on the likelihood of (and potential outcome of) opening AM to the public - they all focus on content.
US AM content is mostly religious, conservative, sportsball and ethnic-usually-Latino. Those are the opposing interests to opening AM. To counter opposition, I'd open the upper half of the AM band to the public. To ease friction, I'd lift any regulatory fees and offer subsidies to offset costs.
As for content on the newly open bands, I could see at least 2 of the current AM interests firehosing cash to saturate the newly open bands and markets (which might unwind over the long term).
It could also power down for a bit. I'm old enough to remember commercial TV going off-air overnight.
Whilst waiting for regulatory change, besides amateur radio station, are there other fun RF things one could do with such a tower's height?
Gherkins and even pickled onions glowed brilliantly. I set up a basic site to share the video we'd taken and details of the experiment, and shared it to B3ta. Sadly all lost to time.
Tangent: I look back sometimes and realise how stupidly lucky I was to have a father who not only humoured my crazy ideas, but actively encouraged them - I only hope I am doing the same for my kids.
That said, the food demodulating the signal into audible noise is badass.
I had opened up a motor controller to fix it, and I knew to discharge the cap before messing around inside. I applied a screwdriver across the terminals to short it out, and was rewarded with a beautiful long and skinny arc as the screwdriver came into contact. I said out loud, "That was cool", and my coworker sitting behind me said, "What was cool"? I told him that I had just shorted out the cap and the arc looked really cool. So he said, "Can you show me?" I said sure, and plugged the controller in for a few seconds to recharge it, then unplugged it and proceeded to repeat what I had just done.
What I had forgotten was that previously the motor controller had been unplugged overnight. When I touched the screwdriver to the freshly charged capacitor, there was a boom, a three inch fireball, and the end of the screwdriver was completely gone. As I sat there thunderstruck, my coworker said, "You're right. That was pretty cool".
Fast forward a few days later I am at school, and I see in one of the outlets one of the prongs for a power cable had broken off in it. I remembered his advice about not touching both sides and proceeded to try and pull it out using my fingers...you can probably imagine what happened. It grabbed hold of me for a few seconds and a lesson was learned.
Even if the tower is off, if it's near any other sites, they can draw a significant amount of RF (as a good AM tower is a good AM antenna) and if it's not grounded, that RF will go through a person too!
This specific tower site doesn't require lights on the shorter towers, so it's not an issue here, but for sites with lights needing replacement, most nowadays turn off power to the tower and ground it before anyone climbs the tower.
I imagine this inspection work is done with camera-equipped quadcopters nowadays.
There's also danger/warning signage around the entire property, on all fences (including those around the towers).
(Vlasic is an American pickle brand.)
What you wrote makes sense from my layman’s understanding. thanks!
What you do feel is the intense burning associated with the RF energy being converted to heat.
(a) a 50kW AM radio station with frequent and accurate traffic updates, often much better detail than what you can get from using google maps or waze or similar, and
(b) massive, frequent traffic problems and congestion at major bridge and tunnel locations.
It's still a very useful thing to have when driving and you don't need to take your eyes off the road at all.
With any modulation scheme, you have the "carrier signal" and the "message signal." The carrier is the frequency you dial into your radio. The message is the thing you listen to - voice, music, whatever. Those two get "modulated" together and blasted out over an antenna, and ta-daa, radio!
Amplitude Modulation is really, really simple. It's literally just the product of the carrier signal by the message signal. The carrier signal is a really high frequency relative to the message, which is where I'm guessing the "resolution" of the signal comes from.
Now, hot dogs.
Hot dogs probably don't resonate very well. Or, maybe they do, but just a little bit at low-ish frequencies - up to a couple thousand Hertz, but no higher. If that's the case, then a hot dog would act like a low pass filter! Since AM is just the product of a high-frequency carrier and a low-frequency message, a low-pass filter could ostensibly leave behind something that resembles the message signal.
Proper AM demodulation involves diodes and whatnot, but I can't imagine a hot dog has semiconductive properties.
Now, if it's an electrical signal, why can we hear it through the hot dog? A hot dog is not a good antenna. It's bad at inducing an electromagnetic field around itself. Instead, it converts the energy from the radio tower into mechanical force - motion, like the way a speaker moves.
All of this could be wrong. Maybe the hot dog isn't serving as a filter, and it is indeed reproducing the AM carrier signal - it's just too high of a frequency for us to hear it. I don't remember my signal processing classes well enough to say for sure. Maybe my whole "hot dog is a speaker" explanation is bunk. Maybe hot dogs really are semiconductors. Not sure.
And the less efficiency you will need in your speaker, aka transducer.
At these conditions there is also no more need for user-supplied power for the audio output to become audible, so no electronic amplification is needed.
As you get closer to the source the need for a carefully crafted, somewhat complex, receiver circuit will diminish, and when there is only one audio program being broadcast on a single radio frequency, no need to discriminate between different frequencies.
In an electronic radio, after the single radio frequency channel has been selected, then the radio frequencies are filtered out before electronic gain is applied to the audio alone. Otherwise audio power would be wasted amplifying radio frequencies that are not audible.
The hot dog emulates all of these requirements, except for the receiver sensitivity that would be needed to respond very strongly from a distance. No noticeable demodulation until it touches the source directly.
Then as a single-component device, a low-efficiency transducer, it conducts the full undemodulated RF power.
Its frequency response as a transducer is probably not even as high as human hearing can go, and people can not hear any RF being reproduced anyway, so all you hear is the audio.
Plus when it comes to hot dog conductivity, who could forget this futuristic home appliance from the 1960's:
Amy demonstrates the Presto Hot Dogger
I've seen at least on video of this being done with a wrench, where the RF current forms a visible arc through the air to the wrench.
But it didn't light up near the tower. It did near the RF circuits above the phasor, though!