That has more to do with the frequency band then the modulation scheme. I wonder if long range FM in the ~1000khz broadcast band would make sense in the future. It would get the range of AM broadcast radio with the quality of FM (but it may require too much bandwidth to be practical)
You're not wrong, but that's useless nitpicking. We're not going to suddenly introduce a brand new radio standard that no-one has a radio for.
There are literally millions of AM radios out there in the US, at the already agreed frequency range. For emergency broadcast uses, the increased quality of FM is meaningless.
The advantage of am over fm is the simplicity of the electronic circuit.
In am its very easy to create a receiver to listen to broadcast. While an fm radio is too complicated for amature electronic.
So i dont belive am will ever be dropped for emergency radio
You can actually receive FM very simply. Here was an amusing post on Reddit [1] a few years ago from someone who was trying to make a simple audio amplifier and found that it was receiving his local NPR station which was broadcasting FM on 88.3 MHz. After some experimenting he got it down to just a cheap op amp, 2 capacitors, 1 potentiometer, a 9 V battery, a speaker, and some wire for an antenna.
It is working through slope detection. Basically if you've got FM at frequency X carrying voice and you measure the energy at a frequency a little bit away from X, as the FM signal frequency varies due to the voice modulation the energy you measure near X will vary in a similar way, so your voice modulation of the frequency X becomes amplitude modulation of your energy measurement.
You can play with this on an SDR, such as a cheap RTL-SDR dongle. Find an FM station and tune to its center frequency with your SDR software set for FM demodulation, and verify that you are indeed on an FM station broadcasting voice and/or music. Then switch the SDR software to AM demodulation and start slowly tuning away from the FM center frequency. You should find a point where you can clearly hear the voice and/or music. It won't sound great compared to FM demodulation of the same station, or compared to an AM station, but it should be serviceable for receiving emergency information.
FM radios aren't complicated at all. And FM transmitters, in particular, are extremely simple. When I was a student we had a tiny one we made in an afternoon (this was decades ago), we connected it to our 8-hour reel tape deck and had our own music station in the car radio when we drove around in the area.
The advantage of AM is, as was mentioned already, the lower frequency used by AM which means much better coverage. FM 87MHz-108MHz is almost just line of sight.
And how is that relevant to the alleged complexity of building an AM radio vs an FM one? The point was that the latter is easy, not complicated. The FM transmitter is so easy to make that you can make one by accident - if there's a non-linear element in the rf part.
It's useless nitpicking because in the US, AM vs FM comes coupled with those frequency ranges. We're as likely to get a brand new radio standard at this point as we are a replacement to the NEMA connector, so the next best thing is to just use the standard we already have that does the job well enough.
If I recall correctly, FM needs the higher frequency carrier band to actually M the F effectively. You'd also need much longer antennas for this. The amplitude-modulated signal also needs far less bandwidth than a frequency-modulated one, so it would not "fit" at ~1000kHz because there are other reserved bands nearby.
The bandwidth is the dealbreaker. Commercial FM radio has a necessary bandwidth of 270KHz. That’s not a lot when your carrier frequency is around 100,000KHz. It’s a whole lot when your carrier is around 1000KHz.
For comparison, commercial AM mono bandwidth is 10KHz. SSB AM ham radios use 2.4KHz.
The broadcast AM band is 1.6MHz wide. Broadcast FM stations are spaced at 200KHz intervals, of which about 150KHz is used for modulation and the remaining ~50KHz is used for guard bands.
Thus, current standards, the entirety of the broadcast AM spectrum can support no more than 8 concurrent FM broadcasts in a region.
And maybe that "works," but it certainly doesn't leave much room for competing markets.
When multiple stations with wide propagation all use a singular frequency, they have to be geographically spaced quite far apart: The hypothetical Toronto station centered at 1330KHz station would step on the Detroit station at the same frequency, which would step on the Chicago and Cincinnati stations.
And, sure: One could give one channel to each market to reduce this co-channel interference, but then there's not enough density for any meaningful competition.
(And our band of capitalism requires competition in order to even begin to work.)