4 ms·

If you don't already know just how low 82 Hz is - then the lowest frequency band you're probably familiar with is AM radio. Which uses around 1,000,000 Hz. And

If you don't already know just how low 82 Hz is - then the lowest frequency band you're probably familiar with is AM radio. Which uses around 1,000,000 Hz. And as others have mentioned, yes, megawatts is a lot. That's the same order of magnitude as what most power plants produce.

bigiain 5y ago
And your power points in your house use 50 to 60Hz, depending on where you're from - and almost nobody even considers that "radio", even though technically it is. Typically antennas for radios are 1/4 wavelength of the transmission frequency long (for various reasons but mostly related to transmission efficiency). So as comparison, the 2.4GHz WiFi/Bluetooth radios in your phone have a 125mm wavelength so probably have 32mm long antennas (most likely folded in interesting ways to make then physically shorter). Old school 27MHz CB radios have an 11m wavelength, so ~2.7m antennas (in practice, at least on car mounted antennas, they'd coil some of that length up at the base out in the middle of they antenna, to keep the size down to 5 or 6 feet.) An 87Hz radio has a 3,500km long wavelength, so would want (for peak efficiency) an antenna almost 1000km long. On top of that, power requirements to get a certain range go up with the square of the distance. Your phone WiFi probably maxes out at 200mW at it's 125mm wavelength and gets maybe 200m or less of max range. It's about 20,000km to get halfway around the planet, so ignoring a bunch of other important things, that's 100,000 times as far you'd need to transmit with 10 billion times as much power to get the same signal strength at that distance. That'd need ~2GW. Your phone battery wouldn't;t last long trying to do that... (There's another complication abiyut the power requirement changing with wavelength, but I'm not quite enough of a radio geek to know that and the numbers I quickly googled up doin;'t make much sense, so...)

bigiain 5y ago

And your power points in your house use 50 to 60Hz, depending on where you're from - and almost nobody even considers that "radio", even though technically it is. Typically antennas for radios are 1/4 wavelength of the transmission frequency long (for various reasons but mostly related to transmission efficiency). So as comparison, the 2.4GHz WiFi/Bluetooth radios in your phone have a 125mm wavelength so probably have 32mm long antennas (most likely folded in interesting ways to make then physically shorter). Old school 27MHz CB radios have an 11m wavelength, so ~2.7m antennas (in practice, at least on car mounted antennas, they'd coil some of that length up at the base out in the middle of they antenna, to keep the size down to 5 or 6 feet.) An 87Hz radio has a 3,500km long wavelength, so would want (for peak efficiency) an antenna almost 1000km long. On top of that, power requirements to get a certain range go up with the square of the distance. Your phone WiFi probably maxes out at 200mW at it's 125mm wavelength and gets maybe 200m or less of max range. It's about 20,000km to get halfway around the planet, so ignoring a bunch of other important things, that's 100,000 times as far you'd need to transmit with 10 billion times as much power to get the same signal strength at that distance. That'd need ~2GW. Your phone battery wouldn't;t last long trying to do that... (There's another complication abiyut the power requirement changing with wavelength, but I'm not quite enough of a radio geek to know that and the numbers I quickly googled up doin;'t make much sense, so...)