Talk:Single-sideband modulation

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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)

[edit] Compatable 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 ?

[edit] Needs work

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)

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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