AM Radio

[TwoForFlinching]

I guess they successfully negotiated a legal limit on the speed of light, eh? AM and FM propagate at the same speed (the speed of light), but the AM wavelengths are reflected by the ionosphere. That’s why you can hear some AM stations from Mexico to Canada—the signal is being bounced back towards Earth by the upper atmosphere.

We're talking two different speeds. It's not a physical speed that differentiates AM and FM, but cycle speed. It's the metric system, 1 Kilohertz (AM wavelength) = 1000 hertz. 1 Megahertz (FM wavelength) = 1000000 hertz.

The faster the cycle, the more data streamed, the clearer the signal, the better the sound... but the shorter the range. Even the most powerful FMs are limited by line of sight due to the curvature of the earth and height of the tower.

The slower the cycle, less data, less fidelity, but the slower signal is able to bounce along between the earth and ionisphere for thousands of miles.

Same principle as ham radio. Slower signals go farther, but are more susceptible to interference. It's also why G. Gordon Liddy always hazed out on Hot Talk 1330 when we plowed near power lines.

 

[docohm]

We're talking two different speeds. It's not a physical speed that differentiates AM and FM, but cycle speed. It's the metric system, 1 Kilohertz (AM wavelength) = 1000 hertz. 1 Megahertz (FM wavelength) = 1000000 hertz.

The faster the cycle, the more data streamed, the clearer the signal, the better the sound... but the shorter the range. Even the most powerful FMs are limited by line of sight due to the curvature of the earth and height of the tower.

The slower the cycle, less data, less fidelity, but the slower signal is able to bounce along between the earth and ionisphere for thousands of miles.

Same principle as ham radio. Slower signals go farther, but are more susceptible to interference. It's also why G. Gordon Liddy always hazed out on Hot Talk 1330 when we plowed near power lines.

It's not slower! It's LOWER frequency for AM than FM. The speed is the same, they are both electromagnetic waves that travel near the speed of light. And AM goes farther because the LOWER frequencies are bounced off parts of the ionosphere while FM (HIGHER freq) goes right through the ionosphere so it's more line of sight.

 

[TwoForFlinching]

It's not slower! It's LOWER frequency for AM than FM. The speed is the same, they are both electromagnetic waves that travel near the speed of light. And AM goes farther because the LOWER frequencies are bounced off parts of the ionosphere while FM (HIGHER freq) goes right through the ionosphere so it's more line of sight.

Brother, you've certainly got spirit and Google isn't lying to you. The difference isn't a physical speed. Think of the AM/FM frequency difference as a difference of bitrate. USB-A vs USB-C. Same power, in the same port, same file, one is slower and one is faster. All the same, the slower/faster talk between them could just be old-timer speak that has become industry standard verbiage.

Also, and more of a fun fact, while we hate the heat waves, the high pressure (heat dome) can cause FM to carry far beyond line of sight. Pressure can capture and carry the frequency. Happens in between cold fronts during winter too, but we've received letters from as far away as Manitoba for our 18kw sister station before. It generally only happens for a few minutes to that extreme though.

 

[Profreedomokie]

I think all car radios should have a NOAA weather receiver built into the radios. My 1996 Land Rover does and an old Volvo a friend had did.