Fifty-some years ago, at about 13 or so years old, I visited with a the father of classmate who was a Ham. I was fascinated. I wanted to be a Ham and get a Technician license because to my mind and experience anyone who was a technician was a well respected professional in electronics. He tried to explain SSB to me. I knew what a sine wave looked like on an oscilloscope and understood AM modulation. So, I kept trying to get him draw me what a SSB signal looked like. I kept trying to figure out what part of the sine wave was missing. I'm sure I didn't understand terms like time-domain and frequency-domain. It ended up with us both being frustrated and him thinking I was an idiot know-it-all. I had a similar low opinion of his teaching skills. Even after seeing Dave's demo, I'm not sure I understand why the time domain display of a SSB signal looks like it does. I'm going to have to perform my own experiment with different tones for modulation and see what it does. First I have to fix my 60 year old 'scope or just buy a new one. I'm amazed that scope Dave used is available on eBay and Amazon (new, shipping included) for $350. 20 years ago, a scope with those capabilities would have cost ten times as much. Now I have to hit Dave's tip jar.
Hi Dave, the SSB waveform can clearly be seen on an oscilloscope when using a 2-tone test, where audio frequencies in the SSB audio pass band are inserted into the microphone input, typically 400 and 1,800 Hz, which is commonly used to measure the linearity of the RF Power amplifier in the transmitter. If the audio tones are exactly at the same amplitude, you will see a waveform that somewhat resembles AM, except the valleys of the signal actually go to zero. The apparent modulation on the oscilloscope will be at a frequency that is the difference between the 2 tones. 73, de AC8AQ
In short, the problem is that the signal envelope is only a part of the SSB time domain signal. To get the full information you'd have to show also phase relative to carrier, or better yet decompose into the two quadratures (one of them is the signal exactly). But either is a way more complex thing than a plain envelope! Still I think for anyone going beyond basic understanding of signals, it's always good to keep in mind the real time domain. A frequency-only understanding is an incomplete one. (Thank you for making this video. I had exactly this same question and this helped me a bit to wrap my head around the answer.)
I've dropped more or less every single other Amateur Radio channel because they are clowns ( Dx Commander is a prime example) , people shilling equipment or morons talking about things they don't understand. However Dave is still on my list because I learn at least something new or useful in EVERY single video. Thanks Dave
WOW Very interesting! Hey Dave: You brought up a great topic/question to ask: The difference of adding vs. mixing a signal... I've seen this on audio forums for mixing sound sources and the discussions blurred so not sure who is right anymore. Thanks and 73's
Dave, missed a great opportunity to explain the relation of time domain to frequency domain being othogonal. (!!!) Take a time domain rf signal (sine wave or envelope) turn it by 90 degrees - look at it from the side (in manner of speaking) - viola - you're in frequency domain!!! try and wrap your mind around it. My microwave professor in college had a visual aid made out of wooden sinewaves to help explain it (he was a radar engineer) it blew my mind.
I think I would have liked to see what a simple voice audio waveform looked like. Watched this twice. Maybe you could explain what the SSB wave is actually showing/doing at the peak and dip. I’d really like to understand this but I don’t. 73
Another thing, the human ear certainly does recognize phase, its how we sense the direction a sound is coming from. we use the phase difference to locate the source. Its a resut evolution, which also gives us a sensitivity peak at 2.5khz, where we detect phase difference best. this is the area which is highest when leaves crackle, and twigs break, helping us to avoid predators. stereo would not work if we couldn't hear phase changes. i suggest you google psychoacoustics.
Yes if course, but you are hearing a phase difference, because you are hearing two different sound sources. If you are listening to only one sound source, a single speaker, or with one ear, then phase changes are not noticable. The visual analog to this is binocular vision and depth perception, because you are comparing two sources of information. There is no depth perception using only one eye, camera, monitor, etc. Received HF signals are *constantly* changing phase because of the path length through the ionosphere is constantly changing, therefore so is the time delay and phase relative to the source, but by itself it's not noticable. An exception to this is Selective Fading, but that is a different phenomenon. 73!
Very good explanation of a complex topic Dave! Phase sensitivity of the human ear very different person to person and baffling as to how it is resolved or perceived. Thanks so much for another very interesting topic and post. 73' de K4WRF
seems to me like, for the upper sideband, if there were simply a single frequency modulation then the frequency domain spectrum diagram in the frequency domain is simply a single spike and therefore the time domain signal would simply be a sine wave with frequency of carrier frequency plus the frequency of the modulating sine wave -> it would simply be a sine wave with a freq of the higher frequency of carrier freq + modulating sine wave freq for multiple sine waves added together in the time domain it would be each sine wave shifted in the same way to car freq + orig freq and then added together in the time domain so I suspect if one recorded some audio and then transmitted it upper sideband it would be like speeding up the recording so all of the freqs were above the carrier freq... it would be a high freq chirp
I'm confused. If we zoom in on the AM time domain waveform we can see the RF (carrier) frequency. What will we see if we zoom in in the SSB time domain waveform?
Hold on hold on. That's not the upper sideband waveform. (Or does USB WAVEFORM actually mean universal serial bus, not upper sideband?) That's a carrier-suppressed or DSB waveform, where the audio modulation crosses zero and goes negative. (Take the AM modulation, then subtract the carrier. That's the same as moving the zero-ref of the cpo tone downwards, so the lower peaks go negative at the modulator output, which, in those places gives us high-freq sine, with negative polarity.) But that's not ssb, not a "USB waveform," instead it's carrier-suppressed only. It's DSB. The SSB upper sideband should look like a 10800KHz CW sinewave, with some slight distortion since the cpo signal isn't pure 800Hz sine. (Take the CW CPO waveform, and uniformly increase its frequency by 10x. It will still appear to be CW on the scope.)
@@ink3n so do I motion always helps i didn't quite get anything out of that dave why couldn't you show a live voice on am fm upper and then lower sideband and let us see for ourselves what it look like in real time with and without sound??? You may have answered the gentlemans question but I guess ghats mine thank you love all your stuff
This was clearly the most interesting video for a very long time - very, very good! But how I wish that you had used the same, pure sine wave for modulation instead of that square wave from the cw training kit, in order to provide direct comparison with the corresponding AM and FM signals. I still wonder what the SSB modulated signal would look like in that case. Could you please, please use your scope again and show us?
If you modulate using a pure sine wave, and then remove one side band and the carrier, you are only left with the spike on the other sideband. A single spike in the frequency domain is effectively a clean carrier wave (but of course shifted from the actual carrier frequency by the modulation frequency).
@@JBuster941 This comment helped me "get it," thank you. I now understand that the information in SSB is not in the amplitude of the resultant signal, but in the offset between the resultant signal and the carrier that isn't transmitted. As the frequency of a given input sine wave increases, so should the frequency of the modulated SSB signal. And I guess that explains why listening to someone on SSB with the tuning slightly off makes them sound so funny! Initially, I started to confuse this offset idea with how FM works - I was about to ask, doesn't FM also send a signal offset the frequency? But I reminded myself that, as a given input sine wave oscillates around the centerpoint, an FM signal will oscillate around its carrier frequency, as opposed to transmitting that signal offset a silent carrier. Thank you, again!
Well i am more confused about SSB than I was before watching, haha. What are the sidebands in relation to the carrier? Where did the information go in that time domain example displayed? Is this like FM almost and it has to do with frequency more than amplitude?
The real magic is how side bands arise in the first place. Consider a steady carrier that is AM modulated with a single sine wave: By just variying the amplitude of a totally steady single-frequency signal a *new* "carrier" signal arises (actually two!) with a slightly shifted frequency - just so. How can that happen, when that shifted frequency seems not present in the time domain at all? Remember, all we did was vary the *strength* of the original carrrier. The *frequency* of that carrier itself stayed exactly the same. That's magic!
Ok - I've given it some more thoughts, and now I think I understand the 'magic' by looking at it this way: First take a single, constant carrier signal of frequency F. Then place another constant carrier (same amplitude) very near by, say, at F+100 Hz. What happens? The two signals interfere: They add to each other 100 times a second, doubling the amplitude (at times when they are in phase) and they also completely cancel each other out 100 times a second (at times when they are in phase opposition). Now: What would that combined signal look like in the time domain? Answer: A 100% amplitude modulated single carrier with frequency F+50 Hz! See it?
I remember as a young boy when I first heard a SSB signal. I really didn't know what the signal was all about? I just knew that it sounded funny like little martians talking! LOL! Thanks, Dave, for presenting this interesting video re: SSB!
I confess SSB seems like magic to me. So you have a carrier, you modulate the carrier with program, then you take the carrier away. What??? What was the carrier for in the first place then? Seems like kicking the ladder away once you've climbed onto the roof. ;)
The human ear doesn't perceive phase?? 😂 How do we tell the direction from which a sound source originates? They say the audio spectrum for humans is around 30Hz to 20,000Hz, which is fine.. But our ability to perceive milliseconds differences between the left and right ear is how we are so good at knowing where a sound is coming from, so long as its not directly in front or behind.. For those sounds we rely on the difference in how the shape of our head muffles/distorts the sound.. 😉
Every time they say "its just an AM signal with the carrier removed" my mind goes clunk clunk. How can you do that? The carrier is what carries it, so I thought. Like riding in the dining car of the train that's not there. Magic, that's what it is. Magic.
A lot of people don't appreciate SSB or DSB variants are amplitude modulation. I always think of sideband as suppressed carrier. Interesting fact if someone is transmitting SSB nearby you can tune in to their carrier. The transmitter can't completely filter out the carrier.
Interesting! I will never lie and say that I get all that high math but I will try, if for no reason I will be able to identify the name of the snake that bit me! :D :D Thank you always, Dave! 73 de N2NLQ
Rubbish. Absolute rubbish. I have looked at plenty of SSB waveforms, and they don't show me "nothing". They look very much like AM, except that since there is no carrier, there is no waveform when there is no modulation. Also, if you modulate with a sine wave, and you have a half-way decent modulator, what you get is something like two out-of-phase sine waves, with the space between them filled. And yes, you can tell what sort of signal the modulation is. Don't broadcast ignorance. Most of your videos are useful. This one is not.
1000'S of monitor scopes were sold by Heathkit, Yaesu, Kenwood and Icom, and any intelligent ham who gives a rats ass, has and uses one to monitor their SSB waveform... it is the only positive way to know you are not over modulating.. The basic concept here is Baloney... Newbies who have only seen waterfall displays and SDR's are like one legged dancers... I won't laugh, that would be cruel. Let me avert my gaze, and wander off in search of intelligent life, elsewhere. W6WUH
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Fifty-some years ago, at about 13 or so years old, I visited with a the father of classmate who was a Ham. I was fascinated. I wanted to be a Ham and get a Technician license because to my mind and experience anyone who was a technician was a well respected professional in electronics.
He tried to explain SSB to me. I knew what a sine wave looked like on an oscilloscope and understood AM modulation. So, I kept trying to get him draw me what a SSB signal looked like. I kept trying to figure out what part of the sine wave was missing. I'm sure I didn't understand terms like time-domain and frequency-domain. It ended up with us both being frustrated and him thinking I was an idiot know-it-all. I had a similar low opinion of his teaching skills.
Even after seeing Dave's demo, I'm not sure I understand why the time domain display of a SSB signal looks like it does. I'm going to have to perform my own experiment with different tones for modulation and see what it does.
First I have to fix my 60 year old 'scope or just buy a new one. I'm amazed that scope Dave used is available on eBay and Amazon (new, shipping included) for $350. 20 years ago, a scope with those capabilities would have cost ten times as much.
Now I have to hit Dave's tip jar.
I'm enjoying these q&a episodes. There's always something to learn from people's questions
Hi Dave, the SSB waveform can clearly be seen on an oscilloscope when using a 2-tone test, where audio frequencies in the SSB audio pass band are inserted into the microphone input, typically 400 and 1,800 Hz, which is commonly used to measure the linearity of the RF Power amplifier in the transmitter. If the audio tones are exactly at the same amplitude, you will see a waveform that somewhat resembles AM, except the valleys of the signal actually go to zero. The apparent modulation on the oscilloscope will be at a frequency that is the difference between the 2 tones.
73, de AC8AQ
This is very well presented
Nice way to discuss this topic as you have done here Dave! Enjoyed it.
In short, the problem is that the signal envelope is only a part of the SSB time domain signal. To get the full information you'd have to show also phase relative to carrier, or better yet decompose into the two quadratures (one of them is the signal exactly). But either is a way more complex thing than a plain envelope!
Still I think for anyone going beyond basic understanding of signals, it's always good to keep in mind the real time domain. A frequency-only understanding is an incomplete one.
(Thank you for making this video. I had exactly this same question and this helped me a bit to wrap my head around the answer.)
I've dropped more or less every single other Amateur Radio channel because they are clowns ( Dx Commander is a prime example) , people shilling equipment or morons talking about things they don't understand.
However Dave is still on my list because I learn at least something new or useful in EVERY single video. Thanks Dave
WOW Very interesting! Hey Dave: You brought up a great topic/question to ask: The difference of adding vs. mixing a signal... I've seen this on audio forums for mixing sound sources and the discussions blurred so not sure who is right anymore. Thanks and 73's
Dave, missed a great opportunity to explain the relation of time domain to frequency domain being othogonal. (!!!)
Take a time domain rf signal (sine wave or envelope) turn it by 90 degrees - look at it from the side (in manner of speaking) - viola - you're in frequency domain!!! try and wrap your mind around it. My microwave professor in college had a visual aid made out of wooden sinewaves to help explain it (he was a radar engineer) it blew my mind.
,So good I watched the video twice. Took me back to my military training nearly 40 years ago...
I think I would have liked to see what a simple voice audio waveform looked like.
Watched this twice. Maybe you could explain what the SSB wave is actually showing/doing at the peak and dip. I’d really like to understand this but I don’t.
73
Another thing, the human ear certainly does recognize phase, its how we sense the direction a sound is coming from. we use the phase difference to locate the source. Its a resut evolution, which also gives us a sensitivity peak at 2.5khz, where we detect phase difference best. this is the area which is highest when leaves crackle, and twigs break, helping us to avoid predators. stereo would not work if we couldn't hear phase changes.
i suggest you google psychoacoustics.
Yes if course, but you are hearing a phase difference, because you are hearing two different sound sources. If you are listening to only one sound source, a single speaker, or with one ear, then phase changes are not noticable.
The visual analog to this is binocular vision and depth perception, because you are comparing two sources of information. There is no depth perception using only one eye, camera, monitor, etc.
Received HF signals are *constantly* changing phase because of the path length through the ionosphere is constantly changing, therefore so is the time delay and phase relative to the source, but by itself it's not noticable.
An exception to this is Selective Fading, but that is a different phenomenon. 73!
Very good explanation of a complex topic Dave! Phase sensitivity of the human ear very different person to person and baffling as to how it is resolved or perceived.
Thanks so much for another very interesting topic and post.
73' de K4WRF
seems to me like, for the upper sideband, if there were simply a single frequency modulation then the frequency domain spectrum diagram in the frequency domain is simply a single spike and therefore the time domain signal would simply be a sine wave with frequency of carrier frequency plus the frequency of the modulating sine wave -> it would simply be a sine wave with a freq of the higher frequency of carrier freq + modulating sine wave freq
for multiple sine waves added together in the time domain it would be each sine wave shifted in the same way to car freq + orig freq and then added together in the time domain
so I suspect if one recorded some audio and then transmitted it upper sideband it would be like speeding up the recording so all of the freqs were above the carrier freq... it would be a high freq chirp
I'm confused. If we zoom in on the AM time domain waveform we can see the RF (carrier) frequency. What will we see if we zoom in in the SSB time domain waveform?
You are just awesome! Thank you for all your informative videos.
Very cool. Need to do more of this. Nice job on it.
It is a pity you did not use a pure tone as input signal. That would have been (more) instructive.
Very informative & well presented. Thanks!
TY
Interesting, the time-domain represented SSB in your oscilloscope looks like the amplitude waves in the bottom picture in your example.
Thanks for the explanations.
I liked the explanation of phase distortion in SSB.
Hold on hold on. That's not the upper sideband waveform. (Or does USB WAVEFORM actually mean universal serial bus, not upper sideband?) That's a carrier-suppressed or DSB waveform, where the audio modulation crosses zero and goes negative. (Take the AM modulation, then subtract the carrier. That's the same as moving the zero-ref of the cpo tone downwards, so the lower peaks go negative at the modulator output, which, in those places gives us high-freq sine, with negative polarity.) But that's not ssb, not a "USB waveform," instead it's carrier-suppressed only. It's DSB.
The SSB upper sideband should look like a 10800KHz CW sinewave, with some slight distortion since the cpo signal isn't pure 800Hz sine. (Take the CW CPO waveform, and uniformly increase its frequency by 10x. It will still appear to be CW on the scope.)
I would have loved to see the oscilloscope live while you transmitted the SSB...
This is a bit complicatet .. because of the permanently changing signal you can‘t trigger a steady window of the waveform to show ^^
@@ink3n I still think it would have helped understanding...
@@ink3n so do I motion always helps i didn't quite get anything out of that dave why couldn't you show a live voice on am fm upper and then lower sideband and let us see for ourselves what it look like in real time with and without sound??? You may have answered the gentlemans question but I guess ghats mine thank you love all your stuff
This was clearly the most interesting video for a very long time - very, very good! But how I wish that you had used the same, pure sine wave for modulation instead of that square wave from the cw training kit, in order to provide direct comparison with the corresponding AM and FM signals. I still wonder what the SSB modulated signal would look like in that case. Could you please, please use your scope again and show us?
If you modulate using a pure sine wave, and then remove one side band and the carrier, you are only left with the spike on the other sideband. A single spike in the frequency domain is effectively a clean carrier wave (but of course shifted from the actual carrier frequency by the modulation frequency).
@@JBuster941 This comment helped me "get it," thank you. I now understand that the information in SSB is not in the amplitude of the resultant signal, but in the offset between the resultant signal and the carrier that isn't transmitted. As the frequency of a given input sine wave increases, so should the frequency of the modulated SSB signal. And I guess that explains why listening to someone on SSB with the tuning slightly off makes them sound so funny!
Initially, I started to confuse this offset idea with how FM works - I was about to ask, doesn't FM also send a signal offset the frequency? But I reminded myself that, as a given input sine wave oscillates around the centerpoint, an FM signal will oscillate around its carrier frequency, as opposed to transmitting that signal offset a silent carrier. Thank you, again!
@@JBuster941 yes of course, I stupid - how could I forget?!
SO? CAN YOU PUT IT ON A SPRECTRUN ANAYLIZER?
Very well, but who owns a spectrum analyzer?
Would it be Okay to see the AM as ladders? Not from the "centerline" but from low end of a vertical ladder to the upper end?
As usual Dave you are very precise and make it interesting. Nice OM OG! 73s.
Yeah. But he is WRONG...see other comments
Well i am more confused about SSB than I was before watching, haha. What are the sidebands in relation to the carrier? Where did the information go in that time domain example displayed? Is this like FM almost and it has to do with frequency more than amplitude?
Well, David, you have me wanting to go out and buy the new Sihuaudon D-808 by Radiwow with RDS on the FM and of course SSB! Thank you, David!
the cw signal IS a ssb signal of a pure sine wave being transmitted
And constant amplitude :)
The real magic is how side bands arise in the first place. Consider a steady carrier that is AM modulated with a single sine wave: By just variying the amplitude of a totally steady single-frequency signal a *new* "carrier" signal arises (actually two!) with a slightly shifted frequency - just so. How can that happen, when that shifted frequency seems not present in the time domain at all? Remember, all we did was vary the *strength* of the original carrrier. The *frequency* of that carrier itself stayed exactly the same. That's magic!
Ok - I've given it some more thoughts, and now I think I understand the 'magic' by looking at it this way: First take a single, constant carrier signal of frequency F. Then place another constant carrier (same amplitude) very near by, say, at F+100 Hz. What happens? The two signals interfere: They add to each other 100 times a second, doubling the amplitude (at times when they are in phase) and they also completely cancel each other out 100 times a second (at times when they are in phase opposition). Now: What would that combined signal look like in the time domain? Answer: A 100% amplitude modulated single carrier with frequency F+50 Hz! See it?
I remember as a young boy when I first heard a SSB signal. I really didn't know what the signal was all about? I just knew that it sounded funny like little martians talking! LOL! Thanks, Dave, for presenting this interesting video re: SSB!
For the love of all that is holy. Look Up A Trapezoid Waveform in the ARRL Handbook !
How about a video on the beverage antenna ?
love your videos but for some reason...just noticed the typewriter in the background!
I use time domain ssb tests all the time, using two tones. its used to set alc. why would anyone think its rare?
Hey David will you look at the reply I made so maybe you can cover it that way I think it was to justin
Um... ok
I confess SSB seems like magic to me. So you have a carrier, you modulate the carrier with program, then you take the carrier away. What??? What was the carrier for in the first place then? Seems like kicking the ladder away once you've climbed onto the roof.
;)
SSB is just baseband shifted up in frequency. All the other stuff is how that is achieved.
The human ear doesn't perceive phase?? 😂 How do we tell the direction from which a sound source originates? They say the audio spectrum for humans is around 30Hz to 20,000Hz, which is fine.. But our ability to perceive milliseconds differences between the left and right ear is how we are so good at knowing where a sound is coming from, so long as its not directly in front or behind.. For those sounds we rely on the difference in how the shape of our head muffles/distorts the sound.. 😉
Every time they say "its just an AM signal with the carrier removed" my mind goes clunk clunk. How can you do that? The carrier is what carries it, so I thought. Like riding in the dining car of the train that's not there. Magic, that's what it is. Magic.
RF is magic. It travels through Universe
Look at your SWR or power meter when keyed up SSB but NOT saying anything into the MIC...
A lot of people don't appreciate SSB or DSB variants are amplitude modulation. I always think of sideband as suppressed carrier. Interesting fact if someone is transmitting SSB nearby you can tune in to their carrier. The transmitter can't completely filter out the carrier.
Sometimes in radio, it's better to just not know.
Add Food industry to that list 🙄
Wow David .., nice why explication..!!, thank a lot..!! , YV6ENB
Interesting!
I will never lie and say that I get all that high math but I will try, if for no reason I will be able to identify the name of the snake that bit me! :D :D Thank you always, Dave!
73 de N2NLQ
The short answer: It's rather deceiving.
Better go over your vidio again eh .
Rubbish. Absolute rubbish. I have looked at plenty of SSB waveforms, and they don't show me "nothing". They look very much like AM, except that since there is no carrier, there is no waveform when there is no modulation. Also, if you modulate with a sine wave, and you have a half-way decent modulator, what you get is something like two out-of-phase sine waves, with the space between them filled. And yes, you can tell what sort of signal the modulation is.
Don't broadcast ignorance. Most of your videos are useful. This one is not.
1000'S of monitor scopes were sold by Heathkit, Yaesu, Kenwood and Icom, and any intelligent ham who gives a rats ass, has and uses one to monitor their SSB waveform... it is the only positive way to know you are not over modulating.. The basic concept here is Baloney... Newbies who have only seen waterfall displays and SDR's are like one legged dancers... I won't laugh, that would be cruel. Let me avert my gaze, and wander off in search of intelligent life, elsewhere. W6WUH
BwaaaHaaa! Agreed sir! WJ5ES
No. Again, no. "Phase distortion"????? No. Oh, I can't listen to any more. Jeez. Never had to downvote you before.
Agreed.