12 ms·

Why does FM sound better than AM?

• ml_comms_eng 2y ago
  There are many differences that explain why one can be better. All else being equal: - bandwidth of modulated signal: it is better to spread the signal over a large bandwidth => Nlog(1+snr) > log(1+Nsnr). the bandwidth used by the FM signal is larger - wasted energy on the DC signal: AM signal is A + s(t) where A > abs(s(t)) to make sure the sent signal is always positive. A (DC) does not carry information so the effective signal to noise ratio of a DC-less signal should be higher (phase/frequency modulation, signalling that can detect the negative part...) - filtering of baseband signal => if you filter too much the original signal, you lose information even before transmission. Voice is usually filtered and 4KHz, but music needs more. FM has more margin (more allocated bandwidth) so can have less stringent filters - tolerance to fading: the wireless channel is not AWGN, it is frequency dependent due to multipath. While radio signals are relatively narrow, signal modulated in frequency are more robust to fading (OFDM...)
• aidenn0 2y ago
  One thing this seems to let out is that in FM, the signal is being broadcast with constant power. A 1MW FM station is always sending 1MW of signal; with AM the signal power varies; if you broadcast in AM powerful enough to mask the noise during periods of typical signal level, then you would still hear noise during quieter than typical periods.
• deleted 2y ago
  [deleted]
• gpderetta 2y ago
  Yet many (if not all?) digital wireless protocols use some form QAM.
  • jdthedisciple 2y ago
    Presumably because there's very little additive white noise inside copper wires
    • gpderetta 2y ago
      emphasis on wireless
      • jdthedisciple 2y ago
        how the hell could i misread like that ... my bad, must've been a long day
• ryanmcbride 2y ago
  The way I had this explained to me when I was in highschool was something like: Imagine someone is shining a flashlight at you through some trees. It's a lot easier to tell what color it is, than how bright it is.
• ianpenney 2y ago
  FM is not very practical on frequencies that bounce off the atmosphere with any regularity as they have a lot less bandwidth to offer. The reason this conversation is so foreign to most of us is because back in the day of shortwave radio our suburban and urban environments weren’t soaked in RF interference. Go out to the middle of nowhere and try a shortwave radio or an SDR with an extremely long wire antenna strung up in trees. You’ll receive the world.
• musicale 2y ago
  I want to know why FM sounds so bad now. Loudness wars or other bad mastering? Broken (or low quality) equipment? Crowded spectrum? Neighboring HD signals? Poor line of sight? Echoes? Interference from other electronics? Low-quality receivers? Lossy compression? Weak signals? Bad/cheap DSP?
• davekeck 2y ago
  I always assumed it was because FM station bandwidths (200kHz) are much wider than AM (10kHz). AM's 10 kHz chops off a lot of human-hearable frequencies.
  • ndndjdjdn 2y ago
    AM doesn't use the frequency for modulation though so it shouldn't matter.
    • t-3 2y ago
      AM does use the frequency, it just doesn't need as much and uses it differently than FM. If it was all at a single frequency, there just be a single tone getting louder and softer.
      • ndndjdjdn 2y ago
        Thanks. I just learned that doing a rabbit hole about sidebands! Still getting my head around it.
        • YZF 2y ago
          Once you change the amplitude of a sine wave (modulate it) it's no longer a side wave. It spreads in the frequency domain. Take the fourier transform of that and you can see the frequency components.
    • kragen 2y ago
      When you amplitude-modulate a carrier wave with an audio signal, you spread it out into a bunch of sum and difference frequencies, as you can see if you use the trigonometric angle-sum formula to factor cos(85000·2πt) · (2 + cos(440·2πt)), a 440-hertz flute being transmitted on 85-kilohertz AM. These so-called "sidebands" mean that the bandwidth of AM does matter, and consequently, using a too-narrow bandpass filter on your AM radio station will result in low-pass filtering your demodulated audio signal.
    • KK7NIL 2y ago
• matrix2003 2y ago
  Someone gave me an analogy some time ago that made a lot of sense. If you shine a flashlight through a tree blowing in the wind and vary the brightness to convey information, the signal can get distorted pretty easily. However, if you have a constant brightness source and vary the color, it’s a lot easier to figure out what the source is trying to convey.
  • MrLeap 2y ago
    I read a similar explanation on slashdot a few decades ago that's stuck with me.
  • crims0n 2y ago
    Wow, that is pretty clever.
  • pessimizer 2y ago
    I'm stealing this.
  • spacemanspiff01 2y ago
    This is the best explanation I have ever heard.
  • userbinator 2y ago
    It's not merely an analogy, just the same EM waves scaled up in frequency by a few orders of magnitude.
    • mistercow 2y ago
      Except that color isn’t the same thing as wavelength when it comes to humans perceiving light, because our eyes only deal with the total energy within each of three overlapping bands. An FM receiver knows the difference between a single carrier varying in frequency, and two carriers of different frequencies varying in proportion. Our eyes don’t, hence the banner above appearing orange, even though it’s actually made of different proportions of red and green.
• johndavid9991 2y ago
  I grew up listening to the radio and was always curious why FM indeed sounds cleaner than AM. My assumption before is that it's setup that way since FM is intended for music stations.
  • timeon 2y ago
    I had AM associated with international broadcast while FM with local one.
  • dylan604 2y ago
    Before FM, all music stations were on AM.
• deleted 2y ago
  [deleted]
• dmitrygr 2y ago
  This is 100% nonsense. Phase noise exists too, not just amplitude noise. The answer is actually rather simple. AM stations are limited to 10KHz band width. FM gets 200KHz. More bandwidth allows representing a higher fidelity signal…
  • basementcat 2y ago
    It’s more than that. FM is several times less spectrum efficient than AM and needs more bandwidth to transmit the same information. https://en.m.wikipedia.org/wiki/Carson_bandwidth_rule https://en.m.wikipedia.org/wiki/Carson_bandwidth_rule
    • IX-103 2y ago
      You provided a citation, but it doesn't prove your point. In general frequency modulation is more efficient than amplitude modulation (but requires more complicated receivers). For example GMSK in the 2G standard GSM replaced the less efficient 1G AMPS system which used amplitude modulation.
  • Stratoscope 2y ago
    Yes, this is the right answer, although I would correct the numbers a bit. If we look only at the audio bandwidth, AM stations are limited to 5 kHz of audio spectrum. The 10 kHz figure comes from the fact that AM is double sideband modulation (as opposed to single sideband as used in ham radio and other radio services). So the broadcast signal uses twice the bandwidth of the audio. FM stations have 15 kHz of audio bandwidth, three times that of AM. They are able to do this because they transmit at a much higher frequency. The 200 kHz figure includes other things like stereo (two channels of audio), subcarriers for RDS data and such, and the "Carson bandwidth rule" that 'basementcat' mentioned. I am surprised that the article overlooked this simple and obvious explanation.
    • deleted 2y ago
      [deleted]
    • nullc 2y ago
• guidedlight 2y ago
  No need to read the article. It’s literally in the name. AM = Amplitude Modulation FM = Frequency Modulation Obviously environmental factors can affect the amplitude of a radio signal. But environmental factors are less likely to affect the frequency.
  • chasil 2y ago
    FM spends bandwidth to reduce noise.
  • kelnos 2y ago
    > Obviously environmental factors can affect the amplitude of a radio signal. But environmental factors are less likely to affect the frequency. I don't think that's "obvious" to most people.
    • zekica 2y ago
      And it's not correct. Resulting frequency due to random noise is also changed, but in FM, noise is less perceivable. There is no such thing as "affecting amplitude" and "affecting frequency" - they are not separate concepts.
• Optimal_Persona 2y ago
  Also the audio frequency bandwidth is narrower on AM, so fewer treble frequencies. TBH I think music from up to the late '60s (especially if originally released in mono) sounds really good, or at least more "era-appropriate" on AM radio. I remember my grandparents tuning in to easy-listening AM stations as I grew up in the '70s and '80s, to my ear Tennessee Ernie Ford's "16 Tons" or a classic Phil Spector "Wall of Sound" production sounds more "right" coming through the AM bands. And, in the age of cellphone speakers and compressed MP3/Bluetooth codecs - I'm not sure how much people actually care about audio quality.
  • kragen 2y ago
    You can use literally any bandwidth with literally any form of radio-wave modulation.
  • epcoa 2y ago
    > And, in the age of cellphone speakers and compressed MP3/Bluetooth codecs - I'm not sure how much people actually care about audio quality Bizarre thing to say after waxing nostalgic about incredibly lo-fi bandwidth limited AM. This is also the age of $9 per month unlimited lossless 24/96 streaming and $1000+ headphone amps.
    • tacticus 2y ago
      they have to justify their non newtonian vibration dampeners (blutak) and custom AC power filter used to play noisy vinyls
  • duped 2y ago
    Look, I'm an audio snob and will talk shit about terrible design of BT headsets that halve bandwidth in duplex until the cows come home. But the reason that codecs have survived this long without substantial changes is because they're far and away good enough (*) for the vast majority of listeners. To the point where today, even trained listeners can't perceive a difference in audio quality between lossless and lossy encoded audio at high enough bit rates (which is 320kbps MP3, or comparable AAC which can be as low as 50% of that). (*) what we don't talk about is the latency of the codec itself, where regardless of available compute resources is still atrocious outside of proprietary codecs. While a listener cannot perceive noticeable differences in fidelity, they can perceive the delay, and this is a problem that doesn't have good solutions outside of specialized equipment today, although OPUS (as a descendant of CELT) is pretty darn good for the cases that consumers care about. Professionals still spend oodles of money on the proprietary gear that have codecs that not even ffmpeg supports. I would go so far as to say there is no practical benefit to uncompressed audio today at all. Lossy is fine for all consumers, and lossless encoding is faster to decode and playback (as well as encode and write) while using less disk/bandwidth than uncompressed for archival purposes.
• massysett 2y ago
  What I’ve never understood is how the FM receiver can lock on to the signal if its frequency is always changing. Doesn’t the receiver need to lock on to something? If the answer is “it locks on to the amplitude, which doesn’t change,” well AM is bad because the amplitude is subject to interference, so wouldn’t FM have the same problem?
  • analog31 2y ago
    One possibility is a phase-locked loop. I don't know if there's anything better. It matches the frequency of a voltage controlled oscillator to the frequency of the incoming signal by detecting the phase mismatch. Then, the control voltage for the VCO becomes the audio signal.
    • rnhmjoj 2y ago
      I don't think radios use a PLL to demodulate the FM audio: the signal has a huge "pilot" tone at 19kHz that you can match to get the first part of the spectrum, mono audio (L+R channels), and at double that frequency you know you'll find the stereo part (L-R channels). Precise phase estimation is only necessary to decode the RDS digital data (station name, datetime, etc.).
      • lrasinen 2y ago
        They do. First of all, the pilot is only required for decoding stereo and RDS. Mono FM does not use a pilot, so obviously there had to be a way to detect FM before stereo came along. I linked to a few of the approaches in a sibling (cousin?) comment. Second, the pilot is embedded in the decoded FM audio. You need to demodulate FM to get to it in the first place. If you look at the waterfall display in an SDR receiver, it might seem like the signal is already present in the original radio frequencies (especially during silent periods), but it's there only indirectly. If you have silence in an FM transmission (say 96.6 MHz), the only audio component present is the 19 kHz pilot signal, which causes the FM radio signal frequency to vary between 96.6 MHz ± k*19 kHz (not sure what's the value for k, but it's not 1). The sine likes to spend most of the time near the extreme values of its range; plot a histogram of a sine wave and you'll see peaks on either end. The waterfall is basically a histogram over frequencies so it gets those peaks as streaks on both sides of the main carrier frequency (plus smaller ones for other components in the signal).
• S_A_P 2y ago
  Lightning is a great example of noise causing amplitude changes and not frequency changes. That’s why during a thunderstorm am radio plays each strike between the station and you. The is usually not any indication of lightning strikes on FM.
• shsbdksn 2y ago
  I always thought about it as I can arbitrarily amplify and saturate the FM signal without changing it.
• dumbo-octopus 2y ago
  Better is in the ears of the beholder. Personally I prefer AM because I can hear multiple stations at once, and hear sources of wideband EM interference in my environment.
  • bigfishrunning 2y ago
    I think this article is focussed on broadcast radio, where crosstalk and em interference are both considered negative properties (not that they're not useful in other applications)
• bdjsiqoocwk 2y ago
  I guess the crux here is the claim that "the effect of random noise is to amplitude modulate". Does anyone here understand why? Ps I don't think analogies are helpful.
  • jmts 2y ago
    AM reception is essentially the direct conversion of the strength (amplitude) of a given radio frequency into an audio signal. Any other noise present at the same frequency is added to the signal (superposition/interference) and therefore impacts the strength of that frequency at the receiver. Therefore it is impossible for the receiver to know whether the amplitude it received is just signal or is signal plus noise. The claim 'the effect of random noise is to amplitude modulate' is probably not 100% correct, because to my understanding it's not actually performing modulation (the modulation happens at the transmitter but the noise happens between the transmitter and receiver), but it is impacting the amplitude at a given frequency and to a receiver this is impossible to know whether said change in amplitude happened before modulation (signal) or after modulation (noise).
• elahieh 2y ago
  It's certainly perceived that way. "Diff'rent Strokes" "Baseball Blues", 1985... Willis does mention stereo is part of the appeal. - Now, Dad, you gotta picture me cruising along in my Mercedes. Head held high. Rocking to the FM stereo. Waving to the chicks. Hey there, mama, looking good. Catch you later, baby. (making engine noises) - You can do all of that in a $4,000 car. (imitating brakes squealing) - Dad, for $4,000 I'll have to slouch way down in my seat so no one can see me. And turn on my AM radio. Wave at the chicks. Hi there, mama, you're looking quite adequate. Chug, chug, chug. - That's just fine, son, chug chug chug means that you won't be spending any of your days in traffic court. - Or any of my nights at a drive-in movie. - Willis, you don't want to date a girl who only likes you for your car. - Sure I do.
• Animats 2y ago
  It's quite possible to have wideband AM radio. Some radio stations did it in the US before the FCC standardized bandwidth and started checking envelopes. Radio Caroline, the UK offshore pirate station (1964-1968), was wideband AM. Noise on AM can to some extent be overcome with power and a low modulation percentage. That's how analog broadcast TV worked. (Broadcast TV was AM video, FM audio.) The black level for the video signal was well above zero. A high black level allowed showing black areas without excessive noise. About 80% of the RF power went into the carrier because of that. Simple, but inefficient. The same trick can be done with AM audio radio, although it seems that's not done much.
  • BoxOfRain 2y ago
    Radio Caroline would be such a good HN topic in its own right. Peter Chicago's name in particular should be up there in hacker lore for some of the things he did to keep Caroline on the air.
• fanf2 2y ago
  Some more about FM at http://www.theradiohistorian.org/fm/fm.html http://www.theradiohistorian.org/fm/fm.html — https://news.ycombinator.com/item?id=41471355 https://news.ycombinator.com/item?id=41471355 « FM signals were much more immune to interference than AM due to its “capture effect” – an interfering signal needed to be more than 50% the strength of the desired signal to cause audible interference, compared to 5% or less with AM. This characteristic would considerably reduce the required separation between stations occupying the same channel and allow more channel re-use, which compensated for its greater occupied bandwidth. And most importantly, because all natural and man-made static is amplitude modulated, FM proved to be amazingly noise-free. Armstrong improved its resistance to noise still further by incorporating a new receiver component – a limiter that stripped off the amplitude variations in the received signal before it reached the detector. He had finally solved the problem of static interference that had confounded radio experts since the beginnings of the art. »
• asdefghyk 2y ago
  because the FM system provides a wider audio bandwidth signal than the audio signal bandwidth provided by AM
  • Johnythree 2y ago
    It doesn't. In both it depends on what the stations engineer chooses to transmit.
• brudgers 2y ago
  And because FM broadcast radio caps audio at 15KHz, a CD “sounds better” than FM…yes, back in the day am SM57 was often good enough.
  • tzs 2y ago
    …if you are young enough. By somewhere around 25 to 30 most people won’t be able to hear above 15 KHz. I’m a little surprised I’ve not seen audio equipment specifically for older people that just covers what they can hear.
    • brudgers 2y ago
      Some plausible reasons: 1. Smaller market than more general market. 2. HiFi is a proven market. 3. “You are dying” is not a great marketing subtext. 4. Digital audio jellybeans produce 20khz and adding a low pass filter adds cost. 5. If a person only hears to 12KHz, there’s no advantage to a low pass filter.
• thadk 2y ago
  This short piece reminds me of a thread about the The Hedgehog and the Fox essay (1953) https://twitter.com/strangeattracto/status/1350600142597054466?s=21 https://twitter.com/strangeattracto/status/13506001425970544... > The idea of code switching between multiple traditions doesn’t seem to occur to a person who is fixated on The One True Aesthetic.
• kazinator 2y ago
  FM sounds better than AM partly because frequency is more durable than amplitude, but it's not the whole story. Frequency does not diminish with the inverse square law, as does the amplitude of a wave that is broadcast in all directions. This is because frequency is related to a count of events over time. Frequency from a source light years away is intact; we can look at frequency bands from a radiating celestial body and know which chemical elements there are, and also tell exactly how fast it is moving away from us from the red shift in that spectral pattern. Be all that as it may, AM should sound great when you are close to the radio tower, and have ideal reception with no multi-path reflections, and good signal/noise ratio. It still doesn't sound good, and that simply because of the bandwidth allocated to it is low. Furthermore, AM Stereo is a retrofit and crams two channels into one via phase modulation. AM stations are separated only by 10 kHz, as you can see on your AM tuner (which you likely have only in your car, if that). The bandwidth is directly related to the audio bandwidth because modulation produces side bands. For instance, if we modulate the amplitude of a 650 kHz carrier with a 1 kHz audio tone, we get side bands of 651 kHz and 649 kHz. You see where this is going? We can only go up to 5 kHz before we bump into the next station, which also needs +/- 5 kHz for its side bands. This 5 kHz limitation is why AM radio sounds like your speakers have a heavy woolen blanket over them. It's almost as bad as the bandwidth limitation as narrow band phone calls. Listening to AM music is almost as bad as listening to on-hold music over a narrow band codec like G.711. The kicker is that only one side band is needed to reconstruct the signal, so in theory AM stations could have 10 kHz bandwith. Unfortunately, SSB was not deployed for broadcast AM, even though it was already known at the dawn of radio. (https://en.wikipedia.org/wiki/Single-sideband_modulation https://en.wikipedia.org/wiki/Single-sideband_modulation has a note about why)
  • brcmthrowaway 2y ago
    Can we use this fact to enable faster than light communication?
    • cj 2y ago
      Not if measuring by relative speed.
    • 2y ago
• raverbashing 2y ago
  There's actually one important factor that's missing: AM radio is limited in bandwidth. The audio is cutting off around 10kHz or such (that's why it kinda sounds like a telephone) > To allow room for more stations on the mediumwave broadcast band in the United States, in June 1989 the FCC adopted a National Radio Systems Committee (NRSC) standard that limited maximum transmitted audio bandwidth to 10.2 kHz, limiting occupied bandwidth to 20.4 kHz (from Wikipedia)
  • usr1106 2y ago
    That's because AM has a bearer around 800 kHz, while FM a bearer around 100 MHz. I guess if doing AM at 100 MHz it wouldn't be a problem granting wider channels, too. But the problem that amplitude is more sensitive to noise wouldn't go away.
• drmpeg 2y ago
  Here's some SDR generated AM with 15 kHz audio bandwidth. Also shows why SSB isn't used for music broadcast. https://www.w6rz.net/am.mp4 https://www.w6rz.net/am.mp4
  • Aloha 2y ago
    Needed an emphasis curve applied to it.
• rob74 2y ago
  TL/DR: because it's frequency modulated and not amplitude modulated, which makes it less susceptible to perturbation.
• twwwt 2y ago
  Define "sound better", please. As we all know this is something subjective - mostly everyone has individual preferences. I would have found it better if the title was "Why is frequency stable in spacetime and amplitude not (which can be verified so easily by listening to audio radio)".
  • analog31 2y ago
    The most familiar definition, though not spelled out in the article, is audio fidelity which is the degree to which the output reproduces the input. It's fair to take this definition as a default, or implied by the article. In this specific case, frequency response and signal-to-noise are both fidelity measures. Also, some of the comments did a better job than the article of explaining things.
• pkolaczk 2y ago
  I don’t buy this explanation. The FM modulation uses a much higher bandwidth than AM. The distance between channels on FM radio is 200 kHz compared to only 9 kHz on AM. That’s more than 20x more bandwidth for FM. On AM, no matter how deeply you modulate the carrier, the bandwidth will not exceed twice the bandwidth of the input signal. On FM, the deeper you modulate it, the wider the output spectrum will be, and it can easily exceed the bandwidth of the input signal. In addition to that, the whole FM band is much higher frequency, while I guess quite a lot of noise, especially burst noise caused by eg thunderstorms is relatively low frequency. So it’s not picked up because it’s out of band. Any noise that falls inside the channel does get picked up by the receiver regardless of modulation. However because the available bandwidth is so much higher than the real bandwidth of the useful signal, there is actually way more information redundancy in FM encoding, so this allows to remove random noise as it will likely cancel out. If I encoded the same signal onto 20 separate AM channels and then averaged the output from all of them (or better - use median filter) that would cancel most of random noise just as well. Also another thing with modulation might be that if there is any narrow-band non-white noise happening to fall inside the channel (eg a distant sender on colliding frequency), on AM it will be translated as-is to the audible band and you’ll hear it as a single tone. On FM demodulation it will be spread across the whole output signal spectrum, so it will be perceived quieter and nicer by human ear, even if its total energy is the same. That’s why AM does those funny sounds when tuning, but FM does not.
  • mannykannot 2y ago
    The context here is the technology available at the time of the introduction of FM in the mid-1930s. In that context, schemes for reduplicating AM over a much wider bandwidth than the ~40 kHz needed for high-fidelity audio may be interesting in their own right, but they have no bearing on the article we are discussing. AM, as it was construed and implemented at the time, was inherently limited to a bandwidth just twice the signal frequency.
  • arghwhat 2y ago
    The wider channels is the source of the available audio fidelity, but wider channels make you more exposed to noise, not less. A wider channel means listening to more noise sources, and having transmitter power stretched thinner for a much lower SNR. In other words, the noise rejection of FM is what enabled the use of wider channels and therefore better audio quality. An analog answer before digital error correction. In FM, the rejection is so strong that if you have two overlapping transmissions, you will only hear the stronger one assuming it is notably stronger. This in turn is why air traffic still use AM where you can hear both overlapping transmissions at once (possibly garbled if carrier wave was off), and react accordingly rather than being unaware that it happened. Technology moved on from both plain AM and plain FM a long time ago, and modern “digital” modulation schemes have different approach to interference rejection.
• fguerraz 2y ago
  > noise tends to be a an unwanted amplitude modulation, not a frequency modulation said someone who didn't understand anything about signal processing. Been debunked so many times: https://physics.stackexchange.com/questions/94198/why-does-noise-affect-fm-radio-less-than-am https://physics.stackexchange.com/questions/94198/why-does-n...
• tsurba 2y ago
  The article kinda sucks as it does not really answer the question it poses. Why ”noise tends to be a an unwanted amplitude modulation, not a frequency modulation”? Is it due to naturally occurring background noise being low frequency high amplitude, showing up as AM? Could the situation change if humans keep generating more high-frequency noise? Or is it just that high frequencies do not travel as far so there will always be relatively little?
• wruza 2y ago
  Because noise is in line with AM and perpendicular to FM? Let’s read if that’s still so. Armstrong reasoned that the effect of random noise is primarily to amplitude-modulate the carrier without consistently producing frequency derivations. …It doesn’t talk much about the noise physics, but basically yes.
• getnormality 2y ago
  Deeper explanations for those who aren't satisfied: https://physics.stackexchange.com/questions/94198/why-does-noise-affect-fm-radio-less-than-am https://physics.stackexchange.com/questions/94198/why-does-n... https://ham.stackexchange.com/questions/6312/why-are-fm-radio-waves-less-susceptible-to-interference-than-am https://ham.stackexchange.com/questions/6312/why-are-fm-radi...
• _1tem 2y ago
  As a non radio engineer, reading this thread on HN is so fascinating because there are so many heated conflicting explanations for a common phenomenon in a well-established technology. I thought this simple question would be settled already. If such disagreement is possible even in an established "hard" science like this, then no wonder some people think everything is subjective.
  • _fizz_buzz_ 2y ago
    This question is of course settled. However, it has more than one aspect and I am pretty sure there are also a lot of rather amateur people chiming in here ... I am an EE, but in power electronics and not an RF engineer so I am a little bit hesitant to comment too much on it, but my understanding is that it mostly breaks down to two aspects: 1) noise interferes more with amplitude 2) the fidelity of the modulating signal in FM is higher (more bandwidth)
  • wellbehaved 2y ago
    HN is not a meritocracy, anyone with an opinion can just chime in and then get upvoted by people who don't really understand what's going on.
• josefritzishere 2y ago
  Back in 2005-ish a Clearchannel enginer, Littlejohn proposed narrowing bandwidth of Am stations to improve the signal to noise ratio. They implemented a 5 Khz bandwidth. Back in the 70s we were all blasting 12 kHz. While that's probably OK-ish for talk, it's dreadful for music. https://www.radioworld.com/columns-and-views/the-5-khz-am-reality https://www.radioworld.com/columns-and-views/the-5-khz-am-re...
  • Aloha 2y ago
    12 kHz AM on a good receiver sounds absolutely fantastic. I have a Royal 51/810 (one of each) that I use as a travel/bathroom radio, ironically, both have fantastic AM performance, and.. lacking FM - the IF/Audio bandwidth appears twice as wide on AM, and FM just sounds like crunchy - probably needs caps in the audio section, but its so tightly packed, and has a PCB with the heaviest plating I've ever seen - which means it needs work I cannot easily do.
    • josefritzishere 2y ago
      Is it packed too tight for a solder sucker to get in there?
      • Aloha 2y ago
        I’d have to figure out how to yank the board. It’s tight.
• ginko 2y ago
  Kinda funny to see people argue AM vs FM when much of the world has already switched to DAB.
• spease 2y ago
  I’m confused how this is even a question. With AM, anything that causes a variation in the intensity of the signal will introduce noise. With FM, anything that causes a variation in the timing of the signal will introduce noise. Unless you’re traveling at relativistic speeds, operating a time dilation device, or colocated with a black hole, you usually aren’t going to see the rate that time flows at vary. Thus if you can make the amplitude of your signal irrelevant past a certain threshold and embed all the information into the time domain, the only thing introducing interference should be other EM sources that happen to be on the same channel.
  • mumer101 2y ago
    https://www.pbs.org/wgbh/aso/tryit/radio/radiorelayer.html https://www.pbs.org/wgbh/aso/tryit/radio/radiorelayer.html
  • _fizz_buzz_ 2y ago
    FM usually has higher fidelity than AM even if no noise is introduced.
    • MBCook 2y ago
      Right. Isn’t FM just flat out higher bandwidth? So unless it’s wasting that somehow it’s just going to carry more information. And for audio, that means sounding better.
      • cruffle_duffle 2y ago
        The use of FM doesn’t inherently imply higher bandwidth. For example, those consumer-grade FRS/GMRS radios you get from Costco use narrowband FM, which typically occupies about 12.5 kHz per channel. This is much narrower compared to the 200 kHz bandwidth used by FM broadcast radio. FM is simply a method of modulating the carrier signal by varying its frequency. The actual bandwidth depends on factors like frequency deviation and modulation, so FM can range from narrow to wide bandwidth depending on the application.
• geocrasher 2y ago
  Bandwidth.