The problem with digital radio is that it's all or nothing.
Analogue degrades gracefully, if you need to listen to the news in an emergency, it doesn't matter if it sounds fuzzy.
Analogue degrades gracefully, if you need to listen to the news in an emergency, it doesn't matter if it sounds fuzzy.
To be fair, if someone made a voice encoding only with that had a lot of error correction bits, it would probably work at much longer distances. Some of the codecs are 2 kilobits per second for human voice? That's got to have a way better margin for the same channel bandwidth than analog decoded by the human brain. This way we get the digital advantage and lossy compression.
MELP targets 2.4kbps, and there are later examples for even lower bitrates (e.g. 1.2kbps, 600bps)
One thing to keep in mind is that a lot of these codecs or technologies are designed to operate at very low bit rates because the signal carrier is required to be capable of operation in "contested environments" where jamming and/or other environmental effects are present (and throughput potential is the tradeoff for assurance).
Especially for speech, there are aggressive and impressive algorithms that can turn a trickle of bits into understandable voice.
> Digital radio remains working at much worse SNR than intelligible fuzzy analog.
Your opus codec needs to demodulate the signal first.
So long as you can get pops of decodable signal, you'll be able to understand what's being said. Using a more robust modulation scheme would also go a long way in improving reach.
AM gets it's range benefits not from the modulation used, but from the frequencies it occupies.
So I dont really understand what this comment has to do with the article at hand here?
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.
So i dont belive am will ever be dropped for emergency radio
Use an amplifier is not a basic circuit. Resistor diode capacitor cable and power source are the basic of electronics
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.
[1] https://www.reddit.com/r/HamRadio/comments/oz5rri/i_accident...
For comparison, commercial AM mono bandwidth is 10KHz. SSB AM ham radios use 2.4KHz.
For AM, that’s 5KHz+-, or 10 total.
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.)
Some fool has downvoted you for making a factual statement.
It is indeed the case that long and medium wave (AM radio) broadcasts have ceased in Ireland and several other countries; FM and DAB only here. Whether this was prudent thing to do for reasons of emergency broadcasting is a different question.
Your point about error correction and perfect quality is noteworthy. Yes, if there is some data loss, error correction can maintain perfect quality, but once that fails, it fails badly. And it's not even all-or-nothing: The radio may, due to an arbitrary firmware configuration, refuse to tune into a stream that is still partially intelligible if it deems the signal integrity or strength to be insufficient. Even very damaged digital streams can be somewhat useful, if you can deal with lovely artifacts like piercing chirping noises when the decoder doesn't know what do to with garbled data.
However an analog signal is ehmm .... an analog of the original. It is continuous. So the error is also analog and you're only limited by the average case. The signal degradation is also analog, there is no sharp cutoff. So as long as human brain can extract the information from the noise, analog continues to work.