Talk:Single-sideband modulation

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Untitled[edit]

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)

Suppressed carrier SSB[edit]

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)

Compatable SSB[edit]

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)

Vestigal sdeband[edit]

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

Needs work[edit]

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 11th paragraph of the DETAILED DESCRIPTION section.  The desired output signal is at 10.74 MHz (see 9th paragraph). The 11th 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. -Splashtalk 03:52, 20 November 2005 (UTC) Bold text

Suppressed Carrier[edit]

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)

Alternate derivation from the frequency domain[edit]

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[edit]

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)