There are areas in the US that do not have cell/data coverage where important road information updates (think mountain pass conditions) are broadcast over AM radio.
Vast areas of the Americas are barren of any FM radio reception but receive AM well. The manufacturers that want to drop AM radio seem to find that fact inconvenient.
I would guess the first two have nothing to do with the type of modulation, but with the frequency bands being used and/or the transmitter power. That is: I would guess it'd work equally well for frequency modulated radio signals broadcasted on those bands with the same transmitters. So those arguments are in favour of using certain specs for broadcasting, but don't seem to require any specific modulation.
(Would love to hear if that's incorrect though)
I'm not sure about DIY'ing a radio - no clue how the modulation complicated things. That could well be a reason favoring AM.
> (think mountain pass conditions) are broadcast over AM radio
This isn't the scientific theory, but I drive the mountains a lot and AM consistently dies much sooner than FM.
Can't explain it, but 100% true.
EDIT: I live in Salt Like City area and drive through the Wasatch Range on a near weekly basis. # of receivable AM stations goes to zero nearly immediately.
AM can be untrustworthy in mountains too. Many factors play in such as how the landscape is actually laid out, the make-up of the rock in the mountain. How signals bounce off the rock, etc. It for sure isn't fool proof. I wouldn't think that much better than AM unless your close to the tower. AM's big advantage is being able to travel farther on less power, but the low frequencies don't have good penetration power. This is why the Navy uses radios that runs on 900+ MHz for shipboard radio, 900 MHz (UHF range) has less distance, but better penetrating power through steel decks. Compared to frequencies that AM operates (HF range). Then there are atmospheric conditions and the cycle of the sun. At a solar maximum sure, but at a solar minimum, probably not.
Generally AM is used in mountainous areas because it's MUCH cheaper than FM, and those areas don't have the population density to make FM stations viable.
It's also used for natural parks, and anywhere you might need updated, local, information, again, because it's so cheap and because receiving is so easy.
Day time vs night time? In the evening while camping in Canada's north in flat or mountainous terrain I've sat beside a fire with a portable radio and tuned to certain high power U.S. stations on the AM radio band. The locals will tell you it is not uncommon. As for reception in a moving vehicle in the daytime, any number of fields or other conditions may be causing the dropouts but in general AM radio propagates vastly farther than FM for a given Effective Radiated Power range specified in the station's license.
cf100clunk|2 years ago
Beldin|2 years ago
1. Range
2. Bouncing off of ionosphere
3. Easy to DIY a radio.
I would guess the first two have nothing to do with the type of modulation, but with the frequency bands being used and/or the transmitter power. That is: I would guess it'd work equally well for frequency modulated radio signals broadcasted on those bands with the same transmitters. So those arguments are in favour of using certain specs for broadcasting, but don't seem to require any specific modulation.
(Would love to hear if that's incorrect though)
I'm not sure about DIY'ing a radio - no clue how the modulation complicated things. That could well be a reason favoring AM.
paulddraper|2 years ago
This isn't the scientific theory, but I drive the mountains a lot and AM consistently dies much sooner than FM.
Can't explain it, but 100% true.
EDIT: I live in Salt Like City area and drive through the Wasatch Range on a near weekly basis. # of receivable AM stations goes to zero nearly immediately.
tcmart14|2 years ago
hguant|2 years ago
It's also used for natural parks, and anywhere you might need updated, local, information, again, because it's so cheap and because receiving is so easy.
cf100clunk|2 years ago