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I am not sure, but as far as I remmber the formulas should be and so , i.e., , thus, while . The first formulas, here in this article, include sines but only the last one include cosines. I scammed the other Wikipedias and I found cosines in every forgin Wikipedia I checked. Am I mistaken? -- Shimonnaim 13:25, 31 March 2007 (UTC)
The FM article uses Image:Frequency-modulation.png as a static image showing the waveform. It seems like it would wise to include the equivalent image for AM on this page: Image:Amplitude-modulation.png. Thoughts? Tacvek 18:20, 29 June 2007 (UTC)
I don't think that the telephone is a good example. We can't consider a baseband medium 'modulated', even with DC bias, IMO. A better example is needed. Or am I missing a historical AM telephone? -- Ktims 07:28, 31 August 2007 (UTC)
I don't think the amplitude modulation index is correctly explained.
See http://www.rfcafe.com/references/electrical/amplitude_modulation.htm —Preceding unsigned comment added by 192.91.172.36 ( talk) 02:08, 2 October 2007 (UTC)
I agree the calculation for the modulation index is obviously wrong because earlier it the article it is explained that A=0 is used for carrier suppression. This equation therefore implies that m = M/0 = infinity when the carrier is suppressed.
Kris —Preceding unsigned comment added by 203.97.235.82 ( talk) 07:49, 8 February 2008 (UTC)
Yes the modulation index is wrong here. If we are using the same definitions as in this article for the carrier wave and the modulation waveform, the modulation index is actually M.
It seems to me this article is very similar or identical in purpose and scope to the Modulation article. Could/should they be merged? -- 166.70.188.26 ( talk) 17:43, 30 June 2008 (UTC)
The depiction of the FM signal is wrong in Fig.1 image (it does not follow the modulating signal). —Preceding unsigned comment added by Gyll ( talk • contribs) 16:54, 6 August 2008 (UTC)
See discussion at Talk:Frequency modulation#Too many animations
This process is known as heterodyning.
This is a small stub gleaned from the original article which suggests that the AM carrier and its two sidebands are merged in a process known as heterodyning. This is a false statement. The sidebands occur as a modulation product just as they do in FM. FM has theoretically infinite sidebands but are of little use other than consuming spectrum space than AM. Actually the process of heterodyning takes place in the radio receiver circuitry. The local oscillator frequency is fed to a circuit called a mixer along with the received signal from the antenna after a preamplifier. This "mixing" of signals is known as heterodyning and produces sums and differences of the received signal and the signal from the local oscillator. Heterodyning has nothing to do with an AM carrier and its adjacent sidebands in a pure sense since the sidebands, carrier or both can be heterodyned with a local oscillator frequency then fed to an IF filter and once again mixed and then finally output to an amplifier for audio with everything except the modulating signal removed. The final ouput from an AM superheterodyne receiver has to be absolutely linear in that the received signal has to be exactly reproduced at the output. FM receivers are much more forgiving since only the frequency has to be preserved, so sloppy, non linear circuits can be used. -- Skywalker45 ( talk) 19:15, 11 November 2010 (UTC)
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link)While I'm no mathematician (which is putting it mildly), I know a little about radio—which I presume this article is trying to address, although it has far too many formulas IMO—and can't get my head around this section. The assertion that each sideband has the same carrier-plus-sidebands as the "fundamental" frequency confuses this concept with DSB-AM and its variants and since the whole negative-frequency thing is speculative to begin with, it just muddies the waters.-- Miniapolis ( talk) 20:22, 26 October 2011 (UTC)
Modulation is a technique by which we can transfer our information at a distance . Science only amplitude phase and frequency of the wave can be changed so we have three basic type of modulation 1.) Amplitude Modulation 2.) Frequency Modulation 3.) Phase Modulation. 1.) Amplitude Modulation : Here the amplitude of the carrier is varied w.r.t variation of the amplitude of the signal wave or original data. 2.) Frequency Modulation : Here the Frequency of the carrier is varied w.r.t variation of the amplitude of the signal wave or original data. 3.) Phase Modulation : Here the phase of the carrier is varied w.r.t variation of the amplitude of the signal wave or original data — Preceding unsigned comment added by 122.173.247.34 ( talk) 05:07, 13 July 2012 (UTC)
Is it correct to say Suppressed-carrier AM is 100 percent power-efficient?
Seems to me that since the information is transmitted twice (two sidebands) it's more like 50% efficient.
Mike ( talk) —Preceding undated comment added 19:58, 2 April 2013 (UTC)
I have made a few changes that hopefully will address the question Mike raises and not add other confusion. I agree with Albany45s comments, but have extended the logic to include all receiver types. The main point being that if you match the transmitted signal to the receiver type, all three systems (AM, DSB, SSB)are 100% efficient, defined as every part of the transmitted signal being useful. Note however that for DSB to be 100% efficient as a system, the sidebands must demodulate coherently so as to add. For AM to be 100% efficient as a system, we must assume an envelope detector. JNRSTANLEY ( talk) 18:15, 18 April 2013 (UTC)
Gah4 asks "Could one have a broadcast system based on DSB-SC with 10% pilot carriers at half the frequency? Or could one define a broadcasting system that transmitted the carrier at reduced (maybe 10%) power?" Having a pilot carrier at half the frequency works for FM stereo where the entire spectrum from DC to the maximum baseband frequency is continuously available, but in over the air broadcasting would be impossible both for frequency allocation reasons and for propagation reasons. DSB-RC with a pilot carrier does save power but requires a complicated receiving setup. It would have been a viable system for communications but not so attractive for broadcasting due to the legacy receiver issue. SSB-RC has been used in broadcasting. With 6 dB carrier reduction the program is intelligible but distorted, and with a phase locked receiver sounds terrific. HCJB used this system for about 10 years on one frequency, 21.455 MHz, a couple of decades ago JNRSTANLEY ( talk) 14:26, 15 October 2016 (UTC)
There are quite a few more methods of generating an AM signal at high power levels, at least six of them I have used in my broadcast engineering career, not counting obsolete methods. I would like to expand this section quite a bit, but wonder if this is something that would merit a page of its own, perhaps under "AM transmitters" or "AM broadcast transmitters". It seems that this section is a subset of "Radio Transmitter Design", which is also quite limited and out of date in its coverage of AM transmitters. Perhaps best to expand under that subject and then modify this presentation a bit with a link to that. I am open to suggestions. JNRSTANLEY ( talk) 18:46, 18 April 2013 (UTC)
This was some time ago, but as well as I can remember, I have already added the material I had in mind. JNRSTANLEY ( talk) 14:11, 15 October 2016 (UTC)
The formula for modulation presented in the "Simplified Example" is incorrect. The equation states that , when the equation is actually . The original equation does not produce a correctly modulated line, but one that is only ever on one side of the x-axis per wave packet. (See https://www.desmos.com/calculator/40yzkqufin, the top graph is the original equation, the bottom graph is the correct one) I took the liberty of fixing it, but I'm not sure quite how to update the Prosthaphaeresi version, so that is probably now incorrect. If somebody knows how to fix the Prosthaphaeresi version or my edit is incorrect, please fix it yourself and/or let me know. Skylord a52 ( talk) 21:08, 6 May 2015 (UTC)
The amplitude of modulating signal frequency is constant the carrier signal is varying by time. — Preceding unsigned comment added by 122.169.186.2 ( talk) 05:51, 13 May 2015 (UTC)
The comment(s) below were originally left at Talk:Amplitude modulation/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
It is a good article.It is usefull if you add a topic in AM generation showing how to give Class C amplifier output to a tuned circuits
yours faithfully shafeeque c 220.225.200.154 ( talk) 06:41, 17 January 2008 (UTC) |
Last edited at 13:31, 10 April 2008 (UTC). Substituted at 07:38, 29 April 2016 (UTC)
I wonder if there should be a reference to modulation methods derived from AM. Specifically, DSB-SC and QAM. There is a {{ citation}} related to its use in computer modems. QAM is widely used in computer modems, and DSB-SC for the stereo subcarrier for FM transmission. Both are modifications to AM. I suspect that enough of a description to give people a reason to link to the appropriate page would be right. In the QAM case, the computer modem use could be added there. A discussion for the reason for the difference in demodulation methods between AM and DSB-SC would also be useful. That is, that the carrier isn't a waste. Gah4 ( talk) 22:49, 13 October 2016 (UTC)
The Czech article seems to include content, particularly in the section cs:Amplitudová_modulace#Typy_amplitudov.C3.BDch_modulac.C3.AD, that could be helpful in understanding the principles of AM and its different types. ZFT ( talk) 19:03, 1 January 2017 (UTC)
Modulation is the process of modifying a carrier wave in accordance with an information signal to be transmitted. Changing the amplitude of the carrier produces AM. — Preceding unsigned comment added by Jibon Krishna ( talk • contribs) 05:08, 13 March 2017 (UTC)
Wireless communication has become an essential part of life in many parts of the world. With the deployment of communication everywhere, it became very crucial to pay attention to its technological betterment. It is essential to address the problems associated with different types of communication channels and to find out probable solutions. When dealing with multipath fading channels, Intersymbol Interference (ISI) occurs during transmission. It is necessary to know the channel characteristics for solving the problems associated with it. Hence researches on channel equalization and channel estimation have been carried out by many researchers. Different kinds of adaptive filtering are used for channel equalization and estimation. However we developed a new algorithm for estimation of a communication channel. In this thesis, a new adaptive filtering is introduced, where the main goal is to improve the performance of the existing algorithms in terms of convergence speed and filtering performance. It is well known that the LMS algorithm has slow convergence for correlated inputs. Moreover its filtering performance and convergence speed are inversely related through a single parameter, the step size. The GLMS algorithm is one of the modified LMS algorithms, which uses single step size but introduces a smoothing parameter which in turn controls its convergence speed and provide better steady state performance. On the other hand, variable step size is used in the LMS algorithm to achieve both fast convergence and a small final excess mean-square estimation error. As a well-studied area, many variations of the LMS algorithm with variable step sizes have been proposed in the literature. A common point in these algorithms is that the step-size computation uses preset control parameters, and sometimes the step size is adapted for every iteration. In this paper, we propose a simple but effective variable step-size adjustment approach, in which only three different step sizes are chosen for filter coefficient adaptation with GLMS algorithm (VSSGLMS). Experiments for the Raised Cosine channel estimation with our proposed VSSGLMS algorithm show the effectiveness in rapidly driving the mean-square estimation error to a small signal steady-state value. We compared our proposed VSSGLMS algorithm with LMS and GLMS algorithms under different parameter settings. From the simulation, we observed that our proposed VSSGLMS algorithm provides better performance in terms of convergence and steady state MSE level. — Preceding unsigned comment added by Jibon Krishna ( talk • contribs) 05:11, 13 March 2017 (UTC)
There is mention in the Applications section on aircraft radio. Being in the VHF part of the spectrum, one might naturally expect them to be FM, like the rest of the VHF radios. As I understand it, they are AM is that allows for one to override, or at least get through enough to get someone else off the air, in an emergency. The FM capture effect tends to block other signals coming in. This might go into the article. Gah4 ( talk) 21:09, 5 April 2020 (UTC)
The reason Aircraft began with AM is that at the time AM was the "standard" mode. FM was not developed until later. Changing all of the equipment at once would be a huge nightmare, so there would have to be a compelling reason to do so. SSB is out of the question as doppler effect from a moving aircraft at VHF would put the various planes calling in on slightly different frequencies, requiring constant tuning. (On HF the need to tune out the doppler is justified as it is typically used by one or a few planes talking to a base, not for ATC and is not enough to make speech distorted. As to FM, the disadvantage of the capture effect covering up weak signals clearly has safety issues. With AM, even a very weak call can be heard as a tone or carrier beat in the receiver under a strong signal, alerting the ATC that a weak station should be stood by for. FM drops out of intelligibility at about the same Signal to noise ratio as AM for narrow deviations. For wide deviations, as used in FM broadcast the threshold signal to noise for intelligibility is worse for FM, but once above it, the audio signal to noise is much better. For aircraft voice narrow deviation would be used. The advantages of any other mode does not justify the cost and danger of problems in a change over, where either every ATC and plane in the world would have to change at once, or else have two systems in place during a change over period. I agree that if the safety issue can be documented it might be added. (Me saying so is not documentation :-) There should have been a govt study of this done at some time. JNRSTANLEY ( talk) 17:58, 9 April 2020 (UTC)
In telecommunications, the term information signal had a very narrow definition, namely that of dial tone, audible ringing tone, busy tone, short announcements, may be a few more. The actual communication payload, voice or audio, is the message signal that is used to modulate. Telephone calls were called messages in standard parlance. The term data signal can also be found in some standard texts, but refers to digital data. kbrose ( talk) 15:20, 30 August 2020 (UTC)
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I am not sure, but as far as I remmber the formulas should be and so , i.e., , thus, while . The first formulas, here in this article, include sines but only the last one include cosines. I scammed the other Wikipedias and I found cosines in every forgin Wikipedia I checked. Am I mistaken? -- Shimonnaim 13:25, 31 March 2007 (UTC)
The FM article uses Image:Frequency-modulation.png as a static image showing the waveform. It seems like it would wise to include the equivalent image for AM on this page: Image:Amplitude-modulation.png. Thoughts? Tacvek 18:20, 29 June 2007 (UTC)
I don't think that the telephone is a good example. We can't consider a baseband medium 'modulated', even with DC bias, IMO. A better example is needed. Or am I missing a historical AM telephone? -- Ktims 07:28, 31 August 2007 (UTC)
I don't think the amplitude modulation index is correctly explained.
See http://www.rfcafe.com/references/electrical/amplitude_modulation.htm —Preceding unsigned comment added by 192.91.172.36 ( talk) 02:08, 2 October 2007 (UTC)
I agree the calculation for the modulation index is obviously wrong because earlier it the article it is explained that A=0 is used for carrier suppression. This equation therefore implies that m = M/0 = infinity when the carrier is suppressed.
Kris —Preceding unsigned comment added by 203.97.235.82 ( talk) 07:49, 8 February 2008 (UTC)
Yes the modulation index is wrong here. If we are using the same definitions as in this article for the carrier wave and the modulation waveform, the modulation index is actually M.
It seems to me this article is very similar or identical in purpose and scope to the Modulation article. Could/should they be merged? -- 166.70.188.26 ( talk) 17:43, 30 June 2008 (UTC)
The depiction of the FM signal is wrong in Fig.1 image (it does not follow the modulating signal). —Preceding unsigned comment added by Gyll ( talk • contribs) 16:54, 6 August 2008 (UTC)
See discussion at Talk:Frequency modulation#Too many animations
This process is known as heterodyning.
This is a small stub gleaned from the original article which suggests that the AM carrier and its two sidebands are merged in a process known as heterodyning. This is a false statement. The sidebands occur as a modulation product just as they do in FM. FM has theoretically infinite sidebands but are of little use other than consuming spectrum space than AM. Actually the process of heterodyning takes place in the radio receiver circuitry. The local oscillator frequency is fed to a circuit called a mixer along with the received signal from the antenna after a preamplifier. This "mixing" of signals is known as heterodyning and produces sums and differences of the received signal and the signal from the local oscillator. Heterodyning has nothing to do with an AM carrier and its adjacent sidebands in a pure sense since the sidebands, carrier or both can be heterodyned with a local oscillator frequency then fed to an IF filter and once again mixed and then finally output to an amplifier for audio with everything except the modulating signal removed. The final ouput from an AM superheterodyne receiver has to be absolutely linear in that the received signal has to be exactly reproduced at the output. FM receivers are much more forgiving since only the frequency has to be preserved, so sloppy, non linear circuits can be used. -- Skywalker45 ( talk) 19:15, 11 November 2010 (UTC)
{{
cite web}}
: External link in |publisher=
and |work=
(
help){{
cite web}}
: Unknown parameter |coauthors=
ignored (|author=
suggested) (
help){{
cite web}}
: External link in |publisher=
(
help){{
cite web}}
: External link in |publisher=
(
help){{
cite book}}
: CS1 maint: extra punctuation (
link)While I'm no mathematician (which is putting it mildly), I know a little about radio—which I presume this article is trying to address, although it has far too many formulas IMO—and can't get my head around this section. The assertion that each sideband has the same carrier-plus-sidebands as the "fundamental" frequency confuses this concept with DSB-AM and its variants and since the whole negative-frequency thing is speculative to begin with, it just muddies the waters.-- Miniapolis ( talk) 20:22, 26 October 2011 (UTC)
Modulation is a technique by which we can transfer our information at a distance . Science only amplitude phase and frequency of the wave can be changed so we have three basic type of modulation 1.) Amplitude Modulation 2.) Frequency Modulation 3.) Phase Modulation. 1.) Amplitude Modulation : Here the amplitude of the carrier is varied w.r.t variation of the amplitude of the signal wave or original data. 2.) Frequency Modulation : Here the Frequency of the carrier is varied w.r.t variation of the amplitude of the signal wave or original data. 3.) Phase Modulation : Here the phase of the carrier is varied w.r.t variation of the amplitude of the signal wave or original data — Preceding unsigned comment added by 122.173.247.34 ( talk) 05:07, 13 July 2012 (UTC)
Is it correct to say Suppressed-carrier AM is 100 percent power-efficient?
Seems to me that since the information is transmitted twice (two sidebands) it's more like 50% efficient.
Mike ( talk) —Preceding undated comment added 19:58, 2 April 2013 (UTC)
I have made a few changes that hopefully will address the question Mike raises and not add other confusion. I agree with Albany45s comments, but have extended the logic to include all receiver types. The main point being that if you match the transmitted signal to the receiver type, all three systems (AM, DSB, SSB)are 100% efficient, defined as every part of the transmitted signal being useful. Note however that for DSB to be 100% efficient as a system, the sidebands must demodulate coherently so as to add. For AM to be 100% efficient as a system, we must assume an envelope detector. JNRSTANLEY ( talk) 18:15, 18 April 2013 (UTC)
Gah4 asks "Could one have a broadcast system based on DSB-SC with 10% pilot carriers at half the frequency? Or could one define a broadcasting system that transmitted the carrier at reduced (maybe 10%) power?" Having a pilot carrier at half the frequency works for FM stereo where the entire spectrum from DC to the maximum baseband frequency is continuously available, but in over the air broadcasting would be impossible both for frequency allocation reasons and for propagation reasons. DSB-RC with a pilot carrier does save power but requires a complicated receiving setup. It would have been a viable system for communications but not so attractive for broadcasting due to the legacy receiver issue. SSB-RC has been used in broadcasting. With 6 dB carrier reduction the program is intelligible but distorted, and with a phase locked receiver sounds terrific. HCJB used this system for about 10 years on one frequency, 21.455 MHz, a couple of decades ago JNRSTANLEY ( talk) 14:26, 15 October 2016 (UTC)
There are quite a few more methods of generating an AM signal at high power levels, at least six of them I have used in my broadcast engineering career, not counting obsolete methods. I would like to expand this section quite a bit, but wonder if this is something that would merit a page of its own, perhaps under "AM transmitters" or "AM broadcast transmitters". It seems that this section is a subset of "Radio Transmitter Design", which is also quite limited and out of date in its coverage of AM transmitters. Perhaps best to expand under that subject and then modify this presentation a bit with a link to that. I am open to suggestions. JNRSTANLEY ( talk) 18:46, 18 April 2013 (UTC)
This was some time ago, but as well as I can remember, I have already added the material I had in mind. JNRSTANLEY ( talk) 14:11, 15 October 2016 (UTC)
The formula for modulation presented in the "Simplified Example" is incorrect. The equation states that , when the equation is actually . The original equation does not produce a correctly modulated line, but one that is only ever on one side of the x-axis per wave packet. (See https://www.desmos.com/calculator/40yzkqufin, the top graph is the original equation, the bottom graph is the correct one) I took the liberty of fixing it, but I'm not sure quite how to update the Prosthaphaeresi version, so that is probably now incorrect. If somebody knows how to fix the Prosthaphaeresi version or my edit is incorrect, please fix it yourself and/or let me know. Skylord a52 ( talk) 21:08, 6 May 2015 (UTC)
The amplitude of modulating signal frequency is constant the carrier signal is varying by time. — Preceding unsigned comment added by 122.169.186.2 ( talk) 05:51, 13 May 2015 (UTC)
The comment(s) below were originally left at Talk:Amplitude modulation/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
It is a good article.It is usefull if you add a topic in AM generation showing how to give Class C amplifier output to a tuned circuits
yours faithfully shafeeque c 220.225.200.154 ( talk) 06:41, 17 January 2008 (UTC) |
Last edited at 13:31, 10 April 2008 (UTC). Substituted at 07:38, 29 April 2016 (UTC)
I wonder if there should be a reference to modulation methods derived from AM. Specifically, DSB-SC and QAM. There is a {{ citation}} related to its use in computer modems. QAM is widely used in computer modems, and DSB-SC for the stereo subcarrier for FM transmission. Both are modifications to AM. I suspect that enough of a description to give people a reason to link to the appropriate page would be right. In the QAM case, the computer modem use could be added there. A discussion for the reason for the difference in demodulation methods between AM and DSB-SC would also be useful. That is, that the carrier isn't a waste. Gah4 ( talk) 22:49, 13 October 2016 (UTC)
The Czech article seems to include content, particularly in the section cs:Amplitudová_modulace#Typy_amplitudov.C3.BDch_modulac.C3.AD, that could be helpful in understanding the principles of AM and its different types. ZFT ( talk) 19:03, 1 January 2017 (UTC)
Modulation is the process of modifying a carrier wave in accordance with an information signal to be transmitted. Changing the amplitude of the carrier produces AM. — Preceding unsigned comment added by Jibon Krishna ( talk • contribs) 05:08, 13 March 2017 (UTC)
Wireless communication has become an essential part of life in many parts of the world. With the deployment of communication everywhere, it became very crucial to pay attention to its technological betterment. It is essential to address the problems associated with different types of communication channels and to find out probable solutions. When dealing with multipath fading channels, Intersymbol Interference (ISI) occurs during transmission. It is necessary to know the channel characteristics for solving the problems associated with it. Hence researches on channel equalization and channel estimation have been carried out by many researchers. Different kinds of adaptive filtering are used for channel equalization and estimation. However we developed a new algorithm for estimation of a communication channel. In this thesis, a new adaptive filtering is introduced, where the main goal is to improve the performance of the existing algorithms in terms of convergence speed and filtering performance. It is well known that the LMS algorithm has slow convergence for correlated inputs. Moreover its filtering performance and convergence speed are inversely related through a single parameter, the step size. The GLMS algorithm is one of the modified LMS algorithms, which uses single step size but introduces a smoothing parameter which in turn controls its convergence speed and provide better steady state performance. On the other hand, variable step size is used in the LMS algorithm to achieve both fast convergence and a small final excess mean-square estimation error. As a well-studied area, many variations of the LMS algorithm with variable step sizes have been proposed in the literature. A common point in these algorithms is that the step-size computation uses preset control parameters, and sometimes the step size is adapted for every iteration. In this paper, we propose a simple but effective variable step-size adjustment approach, in which only three different step sizes are chosen for filter coefficient adaptation with GLMS algorithm (VSSGLMS). Experiments for the Raised Cosine channel estimation with our proposed VSSGLMS algorithm show the effectiveness in rapidly driving the mean-square estimation error to a small signal steady-state value. We compared our proposed VSSGLMS algorithm with LMS and GLMS algorithms under different parameter settings. From the simulation, we observed that our proposed VSSGLMS algorithm provides better performance in terms of convergence and steady state MSE level. — Preceding unsigned comment added by Jibon Krishna ( talk • contribs) 05:11, 13 March 2017 (UTC)
There is mention in the Applications section on aircraft radio. Being in the VHF part of the spectrum, one might naturally expect them to be FM, like the rest of the VHF radios. As I understand it, they are AM is that allows for one to override, or at least get through enough to get someone else off the air, in an emergency. The FM capture effect tends to block other signals coming in. This might go into the article. Gah4 ( talk) 21:09, 5 April 2020 (UTC)
The reason Aircraft began with AM is that at the time AM was the "standard" mode. FM was not developed until later. Changing all of the equipment at once would be a huge nightmare, so there would have to be a compelling reason to do so. SSB is out of the question as doppler effect from a moving aircraft at VHF would put the various planes calling in on slightly different frequencies, requiring constant tuning. (On HF the need to tune out the doppler is justified as it is typically used by one or a few planes talking to a base, not for ATC and is not enough to make speech distorted. As to FM, the disadvantage of the capture effect covering up weak signals clearly has safety issues. With AM, even a very weak call can be heard as a tone or carrier beat in the receiver under a strong signal, alerting the ATC that a weak station should be stood by for. FM drops out of intelligibility at about the same Signal to noise ratio as AM for narrow deviations. For wide deviations, as used in FM broadcast the threshold signal to noise for intelligibility is worse for FM, but once above it, the audio signal to noise is much better. For aircraft voice narrow deviation would be used. The advantages of any other mode does not justify the cost and danger of problems in a change over, where either every ATC and plane in the world would have to change at once, or else have two systems in place during a change over period. I agree that if the safety issue can be documented it might be added. (Me saying so is not documentation :-) There should have been a govt study of this done at some time. JNRSTANLEY ( talk) 17:58, 9 April 2020 (UTC)
In telecommunications, the term information signal had a very narrow definition, namely that of dial tone, audible ringing tone, busy tone, short announcements, may be a few more. The actual communication payload, voice or audio, is the message signal that is used to modulate. Telephone calls were called messages in standard parlance. The term data signal can also be found in some standard texts, but refers to digital data. kbrose ( talk) 15:20, 30 August 2020 (UTC)