3 ms·

I don't understand the bit about the AM radio. Surely he must have meant something in the range of 0.5-1.5 MHz, which is the typical band for AM. I don't think

I don't understand the bit about the AM radio. Surely he must have meant something in the range of 0.5-1.5 MHz, which is the typical band for AM. I don't think a radio broadcast receiver could pick up an EM signal in the sub-20 kHz range.

yetihehe 3y ago
If it had audio amplifier, it could. I remember when I could hear some radio station from simple computer speakers. The catch - transmitter was on the other side of the street, but if I remember correctly, it was FM station - how could a simple audio amplifier pick this up - I have no idea, but strange things can happen with harmonics. It was barely audible and very low quality though.
- fluoridation 3y ago
  My PC speakers do that. I'm pretty sure that's the cable between the sound card and the amplifier acting as an antenna and picking up the broadcast as interference. Then it gets treated by the speaker system as if it was the actual audio signal. Here's the thing, though: either AM or FM, radio broadcasts are definitely not in the human hearing frequency range. EDIT: Thinking about, maybe what he meant is not that the carrier signal is in the sub-20 kHz range, but rather that the switching happens at around that frequency. For example, gates opening and closing modulating the amplitude at audible frequencies.
  - yetihehe 3y ago
    I gave this as an example of what COULD be picked up. Audio-frequency EM (from "processors" running at measly hundreds of kHz, with actual operations at tens of kHz) picked up by crappy audio amplifier in some old radio - that could happen very easily.
ratboy666 3y ago
The first "home computer": Altair 8800. The first peripheral: an AM radio: Steve Dompier - https://www.futurefarmers.com/superfund/gazette/Pop-Ups/Arming-DompieerMusic.html https://www.futurefarmers.com/superfund/gazette/Pop-Ups/Armi... The Altair had a 2Mhz clock.
dredmorbius 3y ago
CPU speed indicates radiation frequency. By the mid-1990s, this was in the FM broadcast range, as a sysadmin I knew at the time demonstrated with an open-cased tower he was working on. (Perhaps perpetually.)

yetihehe 3y ago

If it had audio amplifier, it could. I remember when I could hear some radio station from simple computer speakers. The catch - transmitter was on the other side of the street, but if I remember correctly, it was FM station - how could a simple audio amplifier pick this up - I have no idea, but strange things can happen with harmonics. It was barely audible and very low quality though.

fluoridation 3y ago
My PC speakers do that. I'm pretty sure that's the cable between the sound card and the amplifier acting as an antenna and picking up the broadcast as interference. Then it gets treated by the speaker system as if it was the actual audio signal. Here's the thing, though: either AM or FM, radio broadcasts are definitely not in the human hearing frequency range. EDIT: Thinking about, maybe what he meant is not that the carrier signal is in the sub-20 kHz range, but rather that the switching happens at around that frequency. For example, gates opening and closing modulating the amplitude at audible frequencies.
- yetihehe 3y ago
  I gave this as an example of what COULD be picked up. Audio-frequency EM (from "processors" running at measly hundreds of kHz, with actual operations at tens of kHz) picked up by crappy audio amplifier in some old radio - that could happen very easily.

ratboy666 3y ago

The first "home computer": Altair 8800. The first peripheral: an AM radio: Steve Dompier - https://www.futurefarmers.com/superfund/gazette/Pop-Ups/Arming-DompieerMusic.html https://www.futurefarmers.com/superfund/gazette/Pop-Ups/Armi... The Altair had a 2Mhz clock.

dredmorbius 3y ago

CPU speed indicates radiation frequency. By the mid-1990s, this was in the FM broadcast range, as a sysadmin I knew at the time demonstrated with an open-cased tower he was working on. (Perhaps perpetually.)