Talk:Amplitude modulation

message: I am not sure, but as far as I remmber the formulas should be c(t) = C \cos(\omega_c t)\, and m(t) = M \cos(\omega_m t + \phi)\, so  \ X_{AM}(t)=[C + M(t)]\cos(\omega_c t)=[C + M \cos(\omega_m t + \phi)]\cos(\omega_c t), i.e.,  \ X_{AM}(t)= C\cos(\omega_ct)+{M \over 2} [\cos(\phi +(\omega_m+\omega_c)t)+\cos(\phi +(\omega_m-\omega_c)t)], thus,  \ X_{AM}(t)=C[1+m_a\cos(\omega_mt)]\cos(\omega_ct) while m_a= {M \over C}. 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)
thread_title:  Formulas 

message: 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)
thread_title:  Image 

message: 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)
thread_title:  amplitude modulation index 

message: 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)
replies: text: They are not in any way similar in purpose or scope!  Modulation is an introduction to "all" modulation schemes.  This article covers the maths, theory and application of one specific modulation scheme.  Oli Filth(talk) 19:34, 30 June 2008 (UTC)
thread_title: Merge?

message: 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)
replies: text: Looks ok to me.  Oli Filth(talk|contribs) 17:06, 6 August 2008 (UTC)
thread_title:  Fig.1 is wrong 

message: 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)
thread_title:  Spectrum section 

message: 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)
thread_title:  Modulation   

message: 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)
replies: text: It depends how you define efficiency.  If you demodulate DSB using a USB or LSB receiver, you are losing 50% of the power that goes into the other sideband.  However, if you have an optimal DSB receiver, it combines the power in the two sidebands, and nothing is lost -- 100% efficiency.  I.e., all the transmitted power goes into "useful" modulation with nothing "lost" to a carrier.--Albany45 (talk) 00:43, 3 April 2013 (UTC)

text: As far as I know, this question mostly comes up in the case of the final amplifier for a transmitter. A lot of power is supplied by the amplifier, and then transmitted.  Now, compare to the DSB-SC used for the stereo subcarrier in FM broadcast radio. You couldn't add an AM carrier, and still stay within the other limits for FM.  On the other hand, adding a DSB-SC (left-right) subcarrier to a baseband (left+right) gives the same result as switching between (left) and (right) at 38kHz.  The pilot carrier at 19kHz is needed to demodulate it. 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?  Given modern digital technology, there are many more efficient ways to broadcast audio signals. Receivers that are many years old are still out there, and all would be useless.  For broadcast radio, with many receivers, the power cost per receiver is pretty low. Gah4 (talk) 23:06, 13 October 2016 (UTC)

text: Thanks.  It was a little bit idle thoughts, wondering what might be possible, in theory.  I was ignoring the allocation problem, as that is only a practical problem.  The propagation concern is interesting.  Legacy receiver issue is a problem, but note that it didn't get in the way of the digital television transition. Though I suppose people replace television sets more often than AM radios, especially with the transition away from CRT sets.  In the case of broadcast radio, the power is amortized over a large number of listeners, so the cost isn't all that high. Gah4 (talk) 20:27, 15 October 2016 (UTC)
thread_title:  Carrier-suppressed DSB is 100 percent power-efficient? 

message: 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)
replies: text: Since the article isn't so long, it seems to me that this could be an interesting addition. I suspect you shouldn't go too far into engineering details, though. Can you hint as to what you would say?  Gah4 (talk) 22:39, 13 October 2016 (UTC)
thread_title:  More details on high level generation 

message: Substituted at 07:38, 29 April 2016 (UTC)
thread_title: Assessment comment

message: I wonder if there should be a reference to modulation methods derived from AM.  Specifically, DSB-SC and QAM.  There is a  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)
thread_title:  DSB-SC and QAM 

message: 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)
thread_title:  Importing and translating content from Czech article 

message: 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)
thread_title:  Modulation 

message: 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)
thread_title:  Adapter Filter 

message: 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)
thread_title: Information signal