A scientific curiosity that happened to me

Some family members of mine were in bed in their house during a thunderstorm and during a close lightning strike they heard a few seconds of music that sounded like a radio transmission, somehow being amplified throughout throughout the house as the lightning flashed. I believe their story, and wonder about the mechanism.

>I found out that the radio station's wavelength she was listening to was about 3.3 meters

That's 90MHz, which is in the FM band (at least in the USA). I understand (and have experienced) how this works with AM, but how does this work with FM? Does some circuitry in the headphone act as an FM decoder?

I experienced this just last month! Except, I didn't know it at the moment. I was participating in a design review while wfh on meet. We were having some good discussions, which I participated in. Partway through the meeting I start to fidget a bit and unplug my mic, untwist it from my headphone cable and plug it back in. Next time I unmute, unbeknownst to me, everyone else starts hearing the local radio station. I was using a schiit fulla DAC, and one of its features is auto gain on the microphone. Well I apparently didn't plug the mic in enough and it picked up the local radio station and then boosted the gain enough that it came through loud and clear over the call. Blew my mind once I learned wtf was going on. Embarrassing in the moment as I was muted twice and told to stop listening to a podcast during the meeting.

What's interesting to me is that one particular station came in clearly, given how the difference in broadcast FM allocated frequencies translates into millimeters of antenna length. (e.g. 98.3 vs 98.7 MHz = 3051mm vs. 3039mm)

Just some flexing / coiling of the cord could mean you would favor a different station or get tons of mixing in of other stations.

Maybe the key is that the author / friend was very close to a broadcasting antenna and that overwhelmed any other station that would equally have been received on the headphone cord otherwise?

First sentence of top comment:

> Don't get discouraged by people being a bit condescending, it's a cool discovery.

But as of this moment, my reading returns zero condescending comments. Probably everyone here at HN had the same experience.

So what exactly is lurking deep in this horror movie of a social network?

If you sort by oldest, and click to expand, you suddenly see it. First comment:

> 1.75*2 = 3.5

... with a thread of people having fun at the poster's expense.

To sum up:

* we outsiders from HN are greeted by a pleasant, avuncular top comment followed by enthusiastic discussions by the scientifically curios

* reddit OP was greeted by a terse correction followed by a peanut gallery of asshats (all of which get collapsed and swept under the rug for us outsiders)

This may seem tame, but remember this is only a benign scientific discussion.

If you follow my model here and "look under the carpet" on a post about abortion or trans people, trust me you'll never want to eat at reddit again! :)

Interesting. Reminds me of how if you had a Nokia phone of the time next to computer speakers you could tell when you were about to get a call because the speakers would make a bup-bupbup bup-bupbup sound before the phone itself woke up and rang.

But OP has to be AM, no? Somewhat curious.

I am surprised radio-by-dental-filling is not mentioned here yet ( Lucille Ball )

Mythbusters : https://youtu.be/dZFtrcLGMS0?t=1913

Indeed, in some cases all you need is an antenna, a semiconductor of almost any kind (which can be improvised) and an audio amp. In some cases, it's all-in-one. My family used to talk about a brass headboard that you could hear Morse code from, coming from the local military base.

This happened to an engineer where I worked who had an analog phone with unshielded, untwisted cord exactly the length of the full-wave of the radio station.

It's also worth noting that lightning in the area can induce massive voltage and current impulses in long, unshielded, straight conductors.

I lived next to an AM station before and could hear their broadcasts it in my headphones sometimes.

This is basicaly a "radio that doesn't require any batteries".

It's very easy to build one yourself since only ~5 components are needed and a long-ish wire.

A variable resistor knob is then used to switch between radio stations.

Though it will only catch AM if I'm not mistaken.

> I wrapped the wire around a circular bottle, then counted the number of loops, and then multiplied it by the size of a single turn

Somebody arrest this kid; he's gonna figure out RSA encryption next!

... That's really clever, though. I enjoy this solution.

Bose QC 35 V1 headphones when charging and used passively connected via the headphone jack to an iPad or iPhone also being charged from the same source would pickup audible digital bus noise of the iDevice. Moving the charging sources to different ground planes would solve the problem. It would also happen if devices were being charged by different power adapters connected to the same neutral or ground. This led me to conclude it was a form of ground loop due to a lack of engineering and testing of the headphones.

It is a cool discovery but there's probably a bit more to it

The reason she can hear radio is that there's probably a minor short/oxidizing part that's closing the loop and rectifying the current. Cooper or aluminium oxides would do exactly that for example https://en.wikipedia.org/wiki/Metal_rectifier

The very first electronics circuit I ever built, an audio amplifier, turned out to be sensitive to the local AM radio station, WJOB, 1230 Khz. When I took it to school to show my teacher... the building shielded the signal, and it didn't work. 8(

Only later did I learn why it happened, and how to prevent it.

We had a ball lightning entering the house during a summer thunderstorm. It was only decades later I discovered that this was apparently a very rare event

Are local radio stations sometimes using A.M.?

What's the point of being ham nerds if no one cares what really happened here?

1.65m is FM (90 MHz) which as told is wrong. Can't pick up FM like this, it is NOT simple like all the AM stories.

Chrome books don't have inbuilt radio as far as I can see (Why not is a good question for another time. After the phone cartels destroyed radio on phones why doesn't Google put it in Chromebooks? Would it create awkward questions for their phone cartel department.)

They say coiling it doesn't change it -

  The geometry of the cable does change the sound a little. I can't remember much, but I got the impression it got a little louder when I stretched it, although I could also hear it fine when wrapping it around in circles. Changing the geometry of the wire definetly changes the audio, even if by little

They are in Brazil... not sure if that matters. ( Definitely FM -https://www.wikiwand.com/en/FM_extended_band_in_Brazil)

They didn't hear the FM radio logo, it's a friend who did, so that's not a trustworthy data point. OPs account seems legit, so you could probably trust their personal experiences.

It's probably either a AM re-transmission of FM or an AM station. The cord is not acting as an exact antenna.