Talk:Single-sideband modulation

Untitled

In all of my readings on SSB, I've never come across any mention of using envelope detection to decode SSB, only product demodulation. I was under the impression that the method of demodulation given in this article would not result in the recovery of the original message since still only one sideband is present. Ckape

Unless the article has changed between the time of your comment and now, I think you mis-read it - the article says that envelope detection cannot be used to demodulate SSB, only AM. However, it is possible to demodulate SSB with an envelope detector if you inject a suitable carrier at the receiver. For example, if you were to be receiving an SSB signal with peak signal levels of -120 dBm, and you were to inject a -120 dBm unmodulated carrier at the nominal carrier frequency of the signal into your receiver, then an envelope detector could receive the signal. N0YKG 21:38, 8 September 2005 (UTC)

The only caveat is that the recovered signal will not be ideal -- it will have a certain amount of distortion. algocu (talk) 20:21, 24 June 2020 (UTC)

Suppressed carrier SSB

I deleted the text that said that DSL uses SSB, because I don't know of any type of DSL that does. If someone can give a specific type, it should be listed with more detail. I also observe that the other reference is to ATSC, which in its words uses 8VSB. Because the roll-off factor is so small, this is almost SSB; but because there is content down to DC, it isn't truly SSB. Maybe someone with more expertise can improve it or delete this section as misleading. Many thanks. Serrano24 (talk) 18:57, 2 February 2010 (UTC)

Compatible SSB

Surely it is possible to transmit SSB in a form that can be recieved on AM recievers by transmitting with a carrier reduced by 3dB or with a variant of the vestigal sideband system used in television.

How come broadcasting stations dont use such a system to alleviate frequency band overcrowding ?

There would be no commercial benefit for doing that. Switching to SSB would require replacing all current broadcast receivers. That won't happen without some advantage beyond bandwidth, and SSB has nothing to offer. Digital radio is another alternative, which is far superior to both SSB, AM, and FM, and may eventually take over. Even so, digital radio will have a long hard struggle before it becomes mainstream. --ssd 19:00, 15 July 2007 (UTC)

But the point is that it wouldnt require replacing all current broadcast receivers because as the carrier would only be reduced by 3dB ? 213.40.110.233 (talk) 23:35, 10 January 2009 (UTC)

It's actually a very lame idea, but this talk page is to discuss article contents, not amateur inventions. Dicklyon (talk) 03:47, 11 January 2009 (UTC)

Commercial AM stations actually use each sideband to create stereo signals. The USB gets one channel and the LSB gets the other. On a standard AM receiver, this is summed back to mono, but on a stereo AM receiver, this ends up as a stereo signal. 75.217.204.127 (talk) 17:10, 15 April 2009 (UTC)

Only small portion of the worlds AM stations (mostly in North America) broadcast in Stereo and the majority of these use a phase quadrature rather than Kahn Independent sideband system. 213.40.114.230 (talk) 16:25, 16 October 2009 (UTC)

SSB+vestigial carrier produces distortion in the recovered signal. algocu (talk) 20:24, 24 June 2020 (UTC)

I believe all this talk about CSSB ought to be removed to its own page and wholly rewritten, because it's a fundamentally different methodology from conventional SSB, and nonlinear at that. Also, the long-winded introduction pertaining to its tech has rather obviously been copied here verbatim from researh reports; it might even be against copyright, and it certainly doesn't follow encyclopedic style. Decoy (talk) 21:59, 3 March 2023 (UTC)

Vestigal Sideband

The article could do with more information on vestigal sideband. 213.40.114.230 (talk) 16:25, 16 October 2009 (UTC)

25 years ago I added the following sentence to the Vestigial Sideband paragraph: "The Milgo 4400/48 modem (around 1967) used vestigial sideband and phase-shift keying to provide 4800 bit/s transmission over a 1600 Hz channel." This sentence was written based on personal memory of the the Milgo 4400 rather than any reliable source. I have deleted the sentence as this reference shows that my sentence is wrong. I don't know how many years it will take the ten sites which have copied this sentence to make a correction.Rdmoore6 (talk) 13:48, 17 September 2018 (UTC)

References

Needs work

The use of the Mixing Equations will help explain the mathematics using just cos and sin. The math in its current state is needlessly complicated for an encyclopedic article. --Crcwiki (talk) 18:56, 10 July 2015 (UTC)

The maths is very poorly explained. For example, it is not clear what "j" refers to. All symbols must be explained clearly. —Preceding unsigned comment added by 202.124.67.78 (talk) 16:08, August 24, 2007 (UTC)

I've suppressed some of the maths and the rest of it also looks dubious. This explanation needs a diagram. A Hilbert transform is not the obvious way to explain SSB to our target audience. --Wtshymanski 19:41, 16 November 2005 (UTC)

- Multiple levels of explanation are possible and need not be mutually exclusive. Layering is part of the power of a hyperlinked encyclopedia. It can appeal to a broader audience. Rather than delete the mathematics, you could find or create a more appropriate place for it. Bury it a little deeper. Those who don't want to see it will stop digging when they get beyond their comfort level. --Bob K 03:14, 19 November 2005 (UTC)

- Ah ha! I have discovered subpages. But there seems to be a controversy surrounding their usage. I don't understand what all the fuss is about, but I guess I will find out. So I jumped right in and created a subpage for the suppressed mathematics and linked to it from the article. I named the subpage "Proofs", according to the suggestion at Wikipedia_talk:Subpages. Now I'm going to go catch up on my real job. Keep up the good work, have fun, and good luck. --Bob K 18:10, 19 November 2005 (UTC)

I've also eliminated the word "subhetrodyne" which I've never seen before (neither has Google). --Wtshymanski 19:41, 16 November 2005 (UTC)

subhetrodyne [sic] is not the right spelling, which presumably accounts for the 0 hits. But I agree that it is unusual, and I understand your concern, particularly since super historically derives from supersonic. Or maybe in this century it is time to start putting that archaic modifier to more practical use. Just a thought.

--Bob K 23:23, 17 November 2005 (UTC)

Thanks for the spelling correction, but even typing in "subheterodyne" gives only 6 Google hits, one of which is our very own Wikipedia. The usage is non-standard. It's not Wikipedia's place to create new terms or redefine language. --Wtshymanski 03:16, 18 November 2005 (UTC)

You're welcome, and thanks for all that you do. Also, I believe one of those 6 hits has yet another interpretation. It uses superheterodyne and subheterodyne to respectively describe the sum and difference frequencies produced by the mixer, regardless of whether the injection is high or low. So people look for true meaning in the prefix. It doesn't naturally occur to them that it is just a useless vestige of the naive, early days. Encyclopedias and dictionaries do not redefine or even define language. They just try to keep up with it. --Bob K 16:40, 18 November 2005 (UTC)

"High side" and "low side" works for me, and I believe is commonly accepted ( I'll have to check my ARRL handbook!). And yes, we should keep up with the current usage - but not try to lead it! --Wtshymanski 17:46, 18 November 2005 (UTC)

- My favorite dictionaries are the ones that give all the usages they know about and then explain which one is the "preferred" usage (and hopefully why). In this case especially, I think that would help deter proliferation of the incorrect ones, because people would know that they are incorrect, whereas now they all appear more plausible and more useful than Armstrong's original concept. --Bob K 20:44, 18 November 2005 (UTC)

A good example can be found at http://www.patentstorm.us/patents/5461426.html
In particular the 11^th paragraph of the DETAILED DESCRIPTION section.  The desired output signal is at 10.74 MHz (see 9^th paragraph). The 11^th paragraph describes two techniques:

"... using a lowpass FIR digital filter and a 10.84 MHz oscillator to carry out a superheterodyne ... rather than the bandpass FIR digital filter and the 10.64 MHz oscillator to carry out the subheterodyne...".

Another example is http://www.engr.usask.ca/classes/EE/352/2005/Ch/Ch3-AM-04m4.pdf (excerpt below)

3.22  A 4.02 GHz satellite television signal enters an Earth station receiver with IF frequency 70 MHz. What is the LO frequency and the image frequency for the cases of:

(a) High-side injection (superheterodyne)?

(b) Low-side injection (“subheterodyne”)?

  --Bob K 23:23, 17 November 2005 (UTC)

---

We don't use subpages for this kind of thing, period. The maths needs its language cleaning up, but it should remain firmly in the article. When I have a little mroe time, I will copy it back, and add a cleanup tag. -Splash^talk 03:52, 20 November 2005 (UTC) Bold text

Suppressed Carrier

Why is there a separate page for Single-sideband suppressed-carrier transmission when "single-sideband" almost always refers to that, and is the main modulation technique discussed here? 72.75.98.88 (talk) 06:48, 4 June 2009 (UTC)

It now seems to have been changed to a redirect, which is fine. David Spector (talk) 21:19, 24 March 2015 (UTC)

Alternate derivation from the frequency domain

I think the author of this new section has good intent, but...

It's a false claim that "This approach avoids the use of the complex representation of baseband signals ...", because the proof offered at http://i.imgur.com/xj0moI9.png relies on arguing that:

${\mathcal {F}}^{-1}\{M(f)u(f)\}={\frac {1}{2}}[m(t)+j\cdot {\hat {m}}(t)],$

which is a complex baseband representation. By moving the proof to the RF domain, it simply becomes much more difficult and is not customary. This section is a front for the user's blog, which makes another false implication that it contains fewer "links" than Wikipedia's treatment here. And finally, the links it provides include several seconds of promotional material for something called adf.ly.

--Bob K (talk) 18:51, 24 January 2013 (UTC)

Channel status signals

In the section "History", added "and channel status signalling at or in the vicinity of 3,825 Hz." Akld guy (talk) 01:05, 24 August 2014 (UTC)

I took it out. Bring us a source that explains what it means and maybe we can put it back. Dicklyon (talk) 02:29, 24 August 2014 (UTC)

Means this. When either of the parties hangs up a call or a data transfer is terminated, there needs to be a way to signal to the opposite end that the call is terminated. The presence or absence of the 3.825 KHz signal does that without the need to introduce inband (300Hz-3.4KHz) signals that would be apparent (and LOUD) to the non-hungup party. I thought that those who had already contributed to the page would see instantly what I meant. Perhaps you don't have any actual experience with FDM (aka broadband) systems. I'll try to find a source, but frankly I'm not going to waste a lot of time. If there aren't people here who don't know that OBS (Out of Band Signalling) was used, I'm not going to fight them. My experience consists of quite a few years in the telecoms field, but my terminology may not be appropriate to North American experts. It's what we used in my country, which of course met international standards. I used "at or in the vicinity of 3,825" because while pretty sure that was the frequency, it's been several decades and my recollection may be wrong. Akld guy (talk) 03:41, 24 August 2014 (UTC)

Articulate article?

"in order to support the fidelity required and desired for relative high fidelity, full range clean and articulate vocal audio."

I'm pretty sure the person doing the talking is the one responsible for the audio being articulate or not, not the hardware. Perhaps a different word would better articulate the thought that was intended to be conveyed.

2601:5CE:4101:8553:D0C1:F6:D0C0:3F4C (talk) 03:58, 11 July 2017 (UTC)

Bandwidth of an AM signal

In response to the change by Bob_K ( https://en.wikipedia.org/wiki/User:Bob_K ) at https://en.wikipedia.org/w/index.php?title=Single-sideband_modulation&diff=next&oldid=854177708 , which undoes part of my recent changes, let me explain why I made the changes I made.

Consider an audio signal consisting of a pure tone at 300 Hz with a carrier radio frequency of 10 MHz. The audio signal has a bandwidth of 0 Hz. The resulting AM signal will have components at 9.9997 MHz, 10 MHz, and 10.0003 Mhz, with a bandwidth of 600 Hz, which is not equal to 2 times the bandwidth of the audio signal, but is equal to 2 times the maximum frequency of the audio signal.

Is there something wrong with that example?

If so, we should undo all my changes and clarify matters to avoid my example.

By the way, I don't understand the remark accompanying Bob_K's edit, which was "compare apples (bandwidth) to apples". All the quantities above are measured in Hz, so there is no comparison involving mismatched units.

Daniel R. Grayson (talk) 18:20, 10 August 2018 (UTC)

Your statement "is equal to 2 times the maximum frequency of the audio signal." is correct. I believe we should consistently say it that way. The case of a narrow audio signal (tone, for example) works with this phrasing, but not when we talk about the bandwidth of the audio. Most audio has a BW nearly as wide as the maximum frequency, but certain types of data and MCW do not. I am not totally in favor of saying "audio" instead of the "baseband" or "modulating" frequency since not all modulation is audio, but since most is, I am not against using that term which everyone will understand. JNRSTANLEY (talk) 22:06, 10 August 2018 (UTC)

Thank you for the positive response. I'm not totally in favor of using the term "baseband", because I see problems with the definition at https://en.wikipedia.org/wiki/Baseband -- what does "close to 0" mean? Is an audio signal with frequencies all above 75Hz a baseband signal? I have no way to tell. Daniel R. Grayson (talk) 01:34, 11 August 2018 (UTC)

I see what you mean about the definition of baseband at https://en.wikipedia.org/wiki/Baseband, although near the end of the article under "Modulation" it is correctly explained using audio as an example, and thus seems to call it baseband even without the low audio frequencies. Well how about we stay with "audio" and go back to your last entries on the bandwidth. that is, "equal to 2 times the maximum frequency of the audio signal". Unless Bob K can defend his last edit, I say go back to yours. JNRSTANLEY (talk) 09:56, 11 August 2018 (UTC)

Okay, thanks, let's wait a day or two for Bob_K to chime in. Daniel R. Grayson (talk) 12:00, 11 August 2018 (UTC)

By the way, at https://en.wikipedia.org/wiki/Baseband#Modulation , it is not clearly stated that the lower limit of the audio signal is artificially declared to be 0Hz for the purpose of defining its bandwidth there. Maybe a clarification should be added. Daniel R. Grayson (talk)

Explanation of my comment "compare apples (bandwidth) to apples": My interpretation of Dan's edit was that the difference between "bandwidth" (apples) and "maximum frequency" (oranges) was due to the fact that bandwidth has several possible definitions (even for full-spectrum audio), as does "maximum frequency" for a finite-duration signal (6 dB rolloff?, 12 dB rolloff?, 90 dB rolloff?). I was not considering the case of a baseband tone. I guess if that's what we're going to talk about, it should be more obvious/explicit. Sorry for the misunderstanding.

--Bob K (talk) 15:17, 11 August 2018 (UTC)

Bob_K, thanks!

By the way, in my example above, I was thinking of the audio signal as eternal.

Daniel R. Grayson (talk) 18:49, 12 August 2018 (UTC)

Demodulation

An editor claims that "The carrier recovery doesn't solve the frequency shift. It gives better S/N ratio on the detector output." To my experience, I don't know why this would be the case. It's also not clear what a "BFO oscillator shift" is, or where this "agreement" comes from; 1.7kHz from where to where? In any event, it requires a citation to support the claim. algocu (talk) 20:29, 24 June 2020 (UTC)