Thank you. I am a teacher just beginning to explore radio for various student projects and this was the first video I came across that showed how the process of carrier removal and side band halving worked to be turned into the original signal that I could readily follow and see the changes to the waveforms. Well done and thank you again for the clear explanation.
Thank you for presenting a rational explanation of single-sideband signals that does not require an understanding of calculus. The signals produced by a balanced mixer aren't quite what you describe. They are in fact, F1, F2, F1+F2, and F1-F2, for carrier and modulation frequencies of F1 and F2, respectively. There are no F1+F2*2, F1+F2*3, and so on. The reason you see those frequencies on the spectrum analyzer is due to two things: harmonic distortion in the modulating signal, and nonlinearities in the modulator and stages of RF amplification after the modulator. In your first example at 4:51, you can see that the F2*2 (and its opposite sideband) components are 20 dB below the F2 signal. This is what you should expect to see if your signal generator has just 1% harmonic distortion. But as I said, nonlinearities in the RF path will also cause these sideband components to increase. You mentioned later (11:04) that you were surprised to see odd harmonics but not even harmonics of the modulating frequency in your SSB signal. This is related to they type of distortion in your modulating signal, or the type of nonlinearity in your RF path. Since I assume you're using the same 1 kHz source for both examples, my guess is that the additional signals are being produced mainly by RF nonlinearity. A clue to this is that what you are seeing are only odd harmonics. As you probably know, square waves contain only odd harmonics. So any kind of nonlinearity that behaves like a square wave is likely to show domination by odd harmonics. In practice, "acting like square waves" is what happens when both peaks of your RF signal are being clipped or limited. It is this symmetrical limiting that is the most common nonlinearity in RF amplifiers, and also the reason you see mostly odd harmonics of the modulating frequency in an SSB RF signal. I will also pick a nit with your statement that double-sideband wastes power. It DOES waste spectrum, exactly as you describe, but what I have noticed, using software-defined radio to listen into shortwave broadcasts, is that if you use SSB demodulation to detect an AM signal, you get a lower signal-to-noise ratio than you do when using a DSB demodulator. If you think about that for a moment, the reason becomes clear: by having energy in both sidebands, you are detecting twice as much energy for the same amplitude of signal, just because the DSB detector sums those energies together. So to get the same signal level from an SSB signal, you actually need twice as much energy in that one sideband. You might ask, doesn't the noise also get doubled as well, since your receiver bandwidth is twice as wide? The answer requires more math than I am prepared to present right here, but the noise in a receiver does not increase linearly with bandwidth, but as the square root of the bandwidth. So by using a double-sideband demodulator, you increase the sideband energy by 2, but the noise level by only 1.4 (square root of 2). So in practice, the much more significant advantage of SSB is about bandwidth conservation rather than power conservation. Thank you again.
First, with regard to the observed harmonics. Yes, IF we had a perfectly linear modulator (mixer) and perfectly pure signals to mix, we would have simply F1 +/- F2. However, as you rightly point out (and I mention in the text contained in the video description), we do not have either of these. So, in a real world mixer and with real world signals, we do, indeed, have all of these harmonics to deal with. 😞 Now, with regard to the whole "wasting power" issue. My point was that we are putting power into either redundant "information" or something that does not actively carry information, not that SSB uses less power. If I am transmitting with 100 watts, that power is spread across the entire bandwidth of my transmitted signal. This would include the carrier, if I am using AM. However, if I am using SSB, then this 100 watts is "concentrated" only in the single sideband which contains everything I need. So, in terms of DSB vs SSB, the power density of SSB is twice that of DSB IF I am transmitting with 100 watts in both cases. So, yes, bandwidth conservation ... absolutely. Again, this means that all of my power goes into the information I am looking to communicate. I am not conserving power, but concentrating my power in a single sideband.
Unfortunately, YT does not allow its creators to simply "replace" and existing video or I would refactor this one adding these explanations to it. I can either totally delete the original video with all of its history and the like or I can add a followup video. Unfortunately, few people actually read the description for the additional explanations. So, I suppose that a followup video is in order. I can place a link in the existing video to the followup. I do not know when I will get to it, but I am going to put this in the video queue.
@@eie_for_you I do get it - sorry I didn't see that. What some people do is put any additional explanations/clarifications in the comments, and pin it to be the top comment.
Concur with one additional note: The 2 KHz spacing on the spectrum analyzer suggests IMD, intermodulation distortion, the two sidebands are spaced 2 KHz apart and are probably modulating each other after the output of the modulator; a non-linearity in the buffer amplifier. Many IC amplifiers use a totem-pole arrangement of the output transistors in order to have a bipolar output (with positive and negative voltage swings) and a nonlinearity is essentially unavoidable at the crossover. A simple single-ended buffer stage using a highly linear device (JFET perhaps) and capacitor output would likely remove most of these IMD sidebands.
Very very good video thank you for actually showing and explaining clearly WTF is going on. Every reference I've seen until now just says something useless like "Oh they're duplicated so we can just throw them away". Ok but you cant transmit without the carrier soooooo, thank you for clearing all that up real well. No I understand you can transmit anything and it's about how we modulate in balanced vs unbalanced mixers. Next up to research how the actual maths of those mixers work. How come "balanced" manages to squash the carrier to 0? etc. Thanks again!
Thank you! The most common hardware-type balanced mixer these days is the Gilbert-Cell which actually has a LOT more uses than just a balanced mixer. It s composed of three difference amplifiers. Two of these are cross coupled with the RF being connected to this input. Because they are cross coupled, the one difference amplifier "fights" the other difference amplifier. The resulting output is ... nothing. The third difference amplifier individually controls the current that is allowed to flow through the other two. Remember, the difference amplifier has a bipolar output (Vout+ and Vout-). The audio signal is fed into this third difference amplifier. The balance that maintains the zero output of the other two difference amplifiers is disturbed at the rate of the audio to this third difference amplifier. Thus, the only time that there is an output from the other two difference amplifiers is when there is an audio signal applied to the third. This output, then, varies in amplitude with the amplitude and frequency of the audio signal. I do plan on having a video on this subject. It in my videos to be done queue. 🙂
Imagine Oil Barrel That You Need To Send, The Packing matterial, Boxes, Padding, It Will be Really 4 Times The Size And Weight of It At The End, Now Imagien If You Could Fold The barrel In Two, Imagine Cutting The Barrel In Two, Now You Can Lay In The Other Side Of Other Side Of The Barrel And When You need To Use It Just Unpackc It And Weld It Together, Thats What The SSB Signal Is, Usb Or Lsb, The Unpacking Is DOne By A Program / Modulation, It Unfolds The Barrel Everytime You Need It, But To get A Seal On it You need To Weld It , In Radio Case That Welding And Cutting is Done By A Programs, Low Pass Filter,Band Pass Filters And Other Kind Of Filtering Systems Or Circuit That Is Designed To Do Just That. Frequency Watchers Here, Greetings To Whoever Found This COmment Usefull.
I’d really appreciate a video that covers the circuit theory around the balanced modulator. This video covers a high level overview but not a lot of the electrical engineering around component selection. A good video for its intended purpose.
Yes, it was a high level overview of the mixer itself. I used a "ready made" mixer that exists inside the IC. There is actually several ways that this balanced mixer is implemented, so the discussion can get a bit complicated if we were to cover all of the options. Probably one of the most common implementations used today is the "Gilbert Cell" which consists of a "matrix" of matched transistors and a small number of resistors. I could have a video on this one implementation easily enough. I will add it to my list of videos to produce. In the meanwhile, to satisfy at least some of your curiosity, you can find it here: eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Microwave_and_RF_Design_IV%3A_Modules_(Steer)/06%3A_Mixer_and_Source_Modules/6.03%3A_Single-Ended_Balanced_and_Double_Balanced_Mixers and here: rfic.eecs.berkeley.edu/~niknejad/ee142_fa05lects/pdf/lect18.pdf Hope this helps.
Your comment got my curiosity up and just **HAD** to play a bit. I created a Gilbert Cell balanced mixer using LTSpice (FREE circuit simulation program). Here is a link to my model: drive.google.com/file/d/1CAEdY_aOMJJHIAjicFtPyRCJHNRR45zj/view?usp=sharing It is by no means a perfect design example. I was just thrashing and playing. It was fun and a nice precursor to when I make my video on the subject. Here's the download link for LTSpice: www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html
A lovely explanation, thank you-as a ‘returnee’ to Ham radio after 40 odd years, I need the cobwebs blowing away. All the info is in there..somewhere. This helped bring some of it back!
I am so glad that you found it helpful! 🙂BTW, the extra sidebands beyond the 1 KHz are from harmonic distortion in the audio and non-linearities in the balanced mixer. 🙂
One of the earlier attempts to use the radio spectrum more efficiently. Now we have ctcss and other tones to help. Also trunking systems and other digital communication systems.
Interesting thought. However, we are talking two different things here. SSB is mainly used in HF communications. CTCSS and so on are used with FM modulated signals in the VHF and up range. So, yes, the systems you speak of DO save spectrum space but do not apply to HF. 🙂
This Video Is GOLD, A GOLD I Say, BUT This Video Could Be In 10 Minute Form Easily ! :) But Thank You Anyway, People WHo Are Interested In Radios Will Apriociate Your Video :")
Thanks! 🙂 Yup! There is only so deep one can go in a video this short. I **DO** plan on a video on the Gilbert Cell balanced mixer. It is actually very much in the works. But, admittedly, it will be a few weeks before I get to it.🤓
11:30 The presence of harmonics of the modulating frequency is a defect or deficiency; nearly impossible to avoid but not really part of the balanced modulator process. The more linear the modulator the more perfectly the presence of a pure sinewave modulation will produce exactly one upper sideband and one lower sideband frequency peak. These sidebands can modulate *each other* and since they are 2 KHz apart, that is where your 2 KHz harmonics are appearing, a phenomenon called IMD, InterModulation Distortion. As you can see, these IMD sidebands greatly exceed the expected transmission bandwidth. The absence of 1 KHz sidebands tells me the balanced modulator is highly linear and effective; but the IMD sidebands tells me the buffer amplifier that follows is not perfectly linear and is allowing the upper and lower sidebands to modulate each other. This is also the main difference between one of your top name-brand radios and cheap radios; is how well they resist IMD during receive and avoid it on transmit.
Very true! And, unfortunately, this was a realization which occurred *after* the video was posted and it had a lot of history. I added additional text to the description to this effect. Unfortunately, YT does not allow me to update any given video with a new video. Otherwise, I would have made this note to an updated video. I can only release a completely new video and totally delete the old one, losing ALL of the history (and benefits) of the old one. 😞
Very clear explanation, my friend! Thank you for the time you spent to create this video for the community! Subscribed. Best wishes from southern Italy de IZ7VHF !
@@eie_for_you I add: you also seem to be a good and selfless man, the ideal person with whom I would have liked to have a good glass of wine in the evening, after dinner, to chat about philosophical questions. Have a good luck, my friend, you and the people you care about.
It is evident that you put a great deal of attention, thought and effort into your presentation. And it was a comprehensive refresher that I really enjoyed. There is one question I have about SSB that I've never found a satisfying answer. And tonight I just re-created the experiment that illustrates my question: Transmitting with a FT 747-GX into a dummy load and listening on an Icom 7300 (with headphones) on 80 meters I transmitted my voice in AM and SSB. Comparing the two, AM has a noticeably higher audio quality. It sounds more rich, and I would not be surprised if more of the audio spectrum is being "captured" and "transported" on AM. We know AM is about double the bandwidth of SSB modulation. But, as your video explains, each sideband in traditional AM is a mirror duplicate. And in AM, if I'm not mistaken, the detector diode of a basic receiver only cares about one of the sidebands. For the human audio spectrum: 20hz - 20khz; it seems to me going from 3khz up to 6khz is a bit of a wider of a slice of it. But I'm not convinced it's the increased bandwidth that explains the better audio quality. Is it this, or something else? Thank you.
Really good question ... made me revisit something. If you remember from the video I observed that the double sideband suppressed carrier signal was missing its even harmonic sideband components. I saw only the odd ones at 1 KHz, 3 KHz and so on. I questioned within myself if this was just because of my homebrew balanced modulator. So, I repeated the experiment with my IC-7610. I saw the same thing and then some. So, besides the fact of the phase distortion and narrower audio bandwidth that I mentioned in the video, there is the fact that we lose sideband content. In the case of the IC-7610, there was ONLY the 1KHz sideband whereas AM had 1, 2, 3 and 4 KHz sidebands. I saved the data from my IC-7610 experiment in a spreadsheet and put it into a ZIP file. Here is the link to that zip file: drive.google.com/file/d/1eNx9kYhcokmrtD3wYco1Z4nT0EYcaZDr/view?usp=sharing I hope this satisfies your curiosity.
Hey Benjamin ... I did a deep dive into this whole question and the spectral content of an AM signal and all. I even worked through a mathematical model of AM and did an FFT of the resulting time domain signal. It turns out that the **IDEAL** AM signal will have the carrier with a single pip on either side of the carrier (sidebands). The extra pips at 2xFm, 3xFm, etc represent distortion in the signal. So, it looks like we are left with the audio bandwidth at both the transmitting and receiving end as well as the phase distortion that I originally spoke of in the video.
@@eie_for_you Thanks for the insightful replies and crunching the numbers. I postulate in SSB the lack of fidelity is primarily caused by phase distortion and the audio bandwidth issue is negligible. One way to find out: What if we somehow restricted an incoming baseband audio signal to 3khz going to an amateur transceiver transmitting in AM. And compare this control group to SSB with the spectrum analyzer hooked up to the output of the receiver. No I'm no EE, so I can't back it up with all the math, but what I suspect causes the phase distortion is the reinsertion of the carrier at the receiver. Even if the carrier is reinserted at exactly the right frequency it is no longer in phase. One further reason I suspect it is the phase distortion is: doesn't commercial FM broadcast stereo employ double sideband suppressed carrier? What is the phase reference? I bet it is the pilot tone! Thanks again!
@@margaqrt FM broadcast is Frequency Modulation which, by definition, continuously transmits a carrier plus sidebands on either side of that carrier. I am not sure all of what makes up a Stereo FM Broadcast signal (never paid any attention to it), but it is still FM. The mathematical equation for FM is **FAR** more complex than AM. It almost hurts to think of it. LOL ;-)
Isn’t it also a matter of filter bandwith? On some radios you have the possibility to select the filter regardless of the type of modulation. By doing that effectively you can experience a narrow AM with the “closed” sound to it or a wide and bright SSB audio signal. Thanks for this interesting analysis supported by intuitive examples.
You are very welcome! :-) I just added a link to a ZIP file which has an Excel spreadsheet in it comparing the spectral content of AM, LSB and USB using my IC-7610 in the video description. Here is the link for your convenience if you are interested: drive.google.com/file/d/1eNx9kYhcokmrtD3wYco1Z4nT0EYcaZDr/view?usp=sharing
Thank you for John 3.16 and for Ainos (0:49 - Ainoses were a NATION, not a tribe, in Japan and eastern Asia - nationalized finally by Japaneese. I came here looking for ssb information - i am not even a licenced radio operator :)
You are very welcome on both counts! 🙂Admittedly, I honestly was at a loss for the Ainos reference until I went back to view the video to discover what you were referring to. This was a picture that I downloaded from PIXABAY as an illustration of oldness. Thanks to you, I learned something today! So, thank you! 🙂
Great vid. I understand time domain displays on o-scopes with the HF carrier being shaped by the Base frequency forming the "envelope". What I can't wrap my head around is how does the audio/base "envelope" frequency show up as sidebands on either side of the carrier on spectrum displays. Say, the carrier frequency is 7Mhz - why/how does the base/audio (say 1khz) show up as 7.001Mhz and 6.999 spikes either side? 1khz is way, way below 7Mhz and has no business being there either side of the 7Mhz carrier in my mind.. lol
Gooooood question! Hang on for the answer, because to explain where the sidebands come in, we have to dive into the math to see it. Remember that I said that a modulator is a “multiplier?” Step 1: Our RF is sinusoidal. So we can write the following for the carrier in the time domain: v(t)=Ac*cos(ωc*t) Where Ac is the amplitude of the carrier, ωc is the frequency of the carrier in radians-per-second and t is the time. Step 2: Now we have our modulating signal. We can write a similar equation for the modulating signal: m(t)=M*cos(ωm*t) where M is the amplitude of the modulating signal, ωm is the frequency of the modulating signal in radians-per-second and t is time. Step 3: We modulate! The mathematical equation for Amplitude Modulation will be Vm(t)=Ac*cos(ωc*t)+(M*cos(ωm*t))*cos(ωc*t) Looking at this last portion a little bit, we have the amplitude of the modulating signal times the modulating signal itself times the carrier signal. Now, I pull out the CRC Math tables to find that cos(A) * cos(B) = ½*cos(A-B) + ½*cos(A+B) So, for this last bit of the modulation equation I will set A = ωc*t and B= ωm*t so we get: M*(½*cos(ωc*t - ωm*t) + ½*cos(ωc*t + ωm*t)) = M*(cos((ωc - ωm)*t) + cos((ωc + ωm)*t))/2 Notice the (ωc - ωm) and the (ωc + ωm)! The carrier frequency MINUS the modulating frequency and the carrier frequency PLUS the modulating frequency. The complete equation now looks like this: Vm(t)={Ac*cos(ωc*t)} + {M*(cos((ωc - ωm)*t) + cos((ωc + ωm)*t))/2} Vm(t)={Carrier} + {Sidebands} The first part of the equation is the carrier. The second part of the equation are the sidebands. You can try this in EXCEL (I just did for fun using 250KHz for a carrier and 1 KHz for the modulating signal) and, when you plot a graph of the results, you will see an amplitude modulated signal. At this point, I either blew more fog into the situation or I burned off some of it. Hope it is the latter of the two. 🙂
You and I, and many others, struggle with the same thing. It starts out with “here is the amplitude variation on the oscilloscope” and immediate jumps to “the carrier amplitude is constant and there are the sidebands” on the analyzer. I believe sidebands aren’t real, they only exist because of the analyzer math.
@@nohrtillman8734 I'd politely challenge your disbelief in sidebands being other than a mathematical curiousity by merely stating that analogue SSB radios exist. 😃
Noce prezentation. One of the bigest problem with single sidband recepion is signal phase distortion as propation delay can not be restor by injeting carrier that is not effeted by that. I wonder if pilot signal could be injected to voice sinal (simulat like stereo pilot in FM), so it will still show as SSB (not carrer). Once the signal is demodulated the pilot singnal coul be used are refrence to correct any phase distortion.
Actually, if you look closely, there are sidebands there for double sideband, suppressed carrier spectrum. The problem is that the line is light blue and hard to see.
I'm glad that you enjoyed the video. :-) Well, the reason why no one shows the difference between LSB and USB on the oscilloscope is because there is no difference between LSB and USB as viewed on the oscilloscope. Where the difference is observed in with a spectrum analyzer (frequency domain). Here we can see the LSB envelope below the carrier frequency and the USB envelope above the carrier frequency. In the time domain, there is no difference between the two.
When you listen adults speak on the old Peanuts tv specials, it always sounded to me like SSB without a beat frequency present. I always wondered if that’s what they did to create that distortion.
Playing devils advocate to jump start my brain into understanding this AM frequency shift thing. Oscilloscope = real time representation of a signal. Frequency Analyzer = math applied to the time domain. Does it stand to reason that sidebands only exist because of the Fourier math applied to the real time domain capture?
I liked the video, but am wondering why the frequency domain has multiple peaks beyond the first upper and lower sidebands at 455 +1 and 455-1. Where do the other smaller peaks come from if the audio signal is a pure 1 kHz sine wave. ??
Good question! And, at the time I created the video, I was not remembering some stuff. Those are due to harmonic distortion of the audio and/or the non-linearity of the balanced mixer used to produce the modulated signal. If we had an absolutely pure sine wave and an absolutely, perfectly linear mixer, then there would only be sidebands at 1 KHz either side of the carrier frequency. I made a note of this in the video's description. RUclips doesn't let me "fix" an existing video. 😞 Hope this helps. 🙂
Hello sir, i have a modern radio (XHDATA D808) which has SSB Fine tuning (USB & LSB) functionality, many people say that modern radios doesn't have BFO but how's it possible to recover original signal without re-injecting the carrier signal ?
Yes, the glories of digital signal processing (DSP). They suck the digital samples of the SSB signal into a processor and digitally reproduce the original audio. I am not sure how they do that as I am *definitely NOT* a DSP guy, but they can do amazing things with sampled data.
It isn't and they do. That is to say, the original carrier frequency is mixed with the incoming RF, and this exactly reverses the operation of the double balanced mixer. This can be done digitally by multiplying the samples of RF with samples of the carrier frequency. Since the incoming frequency might be 7.101 and the sampled carrier is 7.100, what will happen is the output of the multiplication will slowly vary in amplitude and this varying will be exactly 1 KHz, the recovered audio frequency. In other words, for a while the samples of RF and the samples of carrier will strengthen ( 2 * 2 = 4) and 1/2 millisecond later they oppose ( -2 * 2 = -4) and midway between these points the math produces zero: ( 0 * 2 = 0). So, analog in a Double Balanced Mixer or digitally in a DSP, works the same way.
Well ... I kinda did. I just didn't call it that (though I probably should have). I talked about how the carrier had to be added back in. This was the job of the Beat Frequency Oscillator. It was a bit difficult to use (I did that on my first receiver, a Hallicrafters SW-25), but it could be done.
Watching your SSB video a question dawned on me. You say the unbalanced modulator produces AM or F1+/- nxF2, meaning harmonics of lower frequencies of the modulating audio end up in the final AM signal. Just as your specan display of 455kHz modulated by 1kHz produced the carrier along with +/- 1Khz, +/- 2kHz, +/-3kHz etc. Does an AM envelope detector remove the additional modulating tones (+/- 2kHz, +/-3kHz etc) or are these extra tones end up as harmonic distortion at the receiver? Same goes with your homemade Balance Modulator that only produced odd harmonics of the 1kHz modulating tone. Can the SSB receiver's product detector remove the "in band" odd harmonics or is harmonic generation (distortion) of low band modulating frequencies integral with all forms of AM?
Actually ... as noted in the video description ... the **ideal** AM modulated signal and DSB modulated signal will only have a single sideband on either side of the carrier frequency. These extra sidebands that we are seeing here represent harmonic distortion that is introduced either with the audio signal source or the modulator itself. 😲 The *ideal* demodulator will faithfully reproduce the audio found on the RF signal, harmonic distortion and all. Reality is, the demodulator itself may also introduce its own harmonic distortion. 🙂
My compliments on your excellent video. I have a question that I feel I should know the answer to. Given the structure of an ssb signal, it seems that as I slowly increase the frequency while listening to a usb signal, the pitch of the voice I'm hearing should slowly increase. Instead, the opposite occurs. Would you please explain why? Thank you.
Good question! Think of it this way ... the frequency of the audio that you hear is relative to the position of the carrier. When you change the frequency that you are listening to, you are changing the position of that carrier while the sidband signal has not moved. Let's say that you are listening to USB. If the carrier is positioned in its original location, then all of the sideband signal is above the carrier position. As you tune up in frequency, you are increasing the frequency of the injected carrier which is moving it closer to the unmoving sideband signal. Its *relative* position is closer and, thus, the audio frequency goes down. Hope this helps dispel the mystery. 🙂
Thank you very much - this has been bugging me. One follow-up if you don't mind - the "injected carrier" you reference is injected by the receiver, correct? @@eie_for_you
Good observation! Yes, this is harmonic distortion which exists either because of an imperfect audio source or an imperfect modulator or both. The AM signal was generated using my Rigol Signal Generator and its internal audio source. The DSB signal was generated using the modulator I built and the audio source is my Tenma signal generator. I have not pursued trying to figure out where the fault lay yet. 🙂
I’m going to ask what may be a possibly dumb question, why doesn’t 2m and 70 cm just operate Single Side Band instead of FM? I feel like this would be a more efficient use of frequency allocation and energy
Your question is not dumb. Most of my experience was with 2m, so that informs my comments. The band covers 144- 148 MHz, which is a large piece of spectrum that has never been very crowded compared to the HF bands. Large portions of 2m have never been regularly utilized, so any transmission mode would not be an issue with respect to spectrum crowding. Since most communication on VHF and UHF bands is line of sight, NBFM produces a higher quality received signal in mobile and portable operation. Equipment, both transmit and receive, is relatively simple to implement (compared to SSB) and small vertical antennas work well when communication takes place through a repeater. On the other hand, DX is possible on 2m when certain atmospheric conditions are present or when bouncing signals off the moon or Aurora Borealis. In those circumstances, CW and to a limited extent SSB are superior. I got my ham license in the early 60s while I was in 9th grade. I was interested in the technical aspect of the hobby and not very keen on CW. With a Technician license, I could operate phone on 2m and that's where I started with a Heathkit Twoer (lunchbox) AM transceiver. It only put out about 1 watt and had a super regenerative receiver which wasn't very good (broad as a barn and deaf to all but the strongest signals). As time went on, I bought brand new Army surplus ARC5 receiver for $15 and built a 6CW4 nuvistor converter. Now I could hear a lot better, but nobody could hear me. Thanks to another local ham and great army surplus parts availability, I built a linear power amplifier from a donated 829B tube. I used the twoer to drive it and started increasing my reach to stations further away. Soon I noticed SSB activity and wanted to contact those stations as well. I found an article in CQ magazine that described how to build a 6m SSB transmitter. I scrounged enough parts to put it together, but needed a way to get it on 2 meters. QST published an article on how to build a 6m to 2m transmitting converter, so I built it. Soon I was on 2m SSB with about 60 watts from the 829B linear and was making contacts deep into Ohio, Ontario and western NY (I'm in Michigan). I was hearing stations running more power but they couldn't hear me. By now I was a senior in high school and when I graduated, my parents gave me a 60' tower as a graduation present. My dad and I erected it and put an 8 element beam on top. I still needed more power and started gathering parts to build a linear amp based on a pair of Eimac 4CX250Bs. I met a lot of great hams locally, and one gave me a pair of used tubes which made it possible for me to finish the amp. I worked 13 states on 2m SSB with some of them via the Aurora (point the antenna north and listen for ghostly CW signals or SSB that sound like whispers). College and other interests displaced my ham radio days and I gave all of my equipment away. After I left home, my dad sold the tower. I never got bitten by the 2m NBFM and repeater bug, but my senior design project in college was to design and build a 2M NBFM transceiver which sits on the shelf today. I think 2m NBFM killed a lot of the potential for 2m SSB, kind of like MTV killed the radio DJ!
If your mixer / modulator were clean, you wouldn't have pips at the harmonics away from the carrier, only the fundamental. You're getting those harmonic pips because your modulator is distorted creating harmonic products.
You are absolutely correct! :-) I discovered this fact AFTER I posted the video and added comments to this effect in the description. Thank you for pointing that out. Always learning we are!
Hi Ralph, nice video. it’s not immediately obvious to me why the unbalanced mixer takes F1 and F2 as inputs but puts out all of those n*F2 harmonics. Anything on that?
A good question ... and you are not the first to ask. The answer is two-fold. First, there could be some harmonic distortion in the modulating audio. Second, there could be some non-linearity in the mixer itself. Being that the AM and the DSB use different audio sources and the modulation is being accomplished with two different mixers, this would explain the difference in the harmonic content of the spectrum. Hope this helps.🙂
@@DaylightRobberyCA The thing to remember ... we are not talking D.C. here. We have to remind ourselves that we are talking R.F. and capacitance and inductance and so on. As such, the coax is part of the circuit "components" that make this up. That's all I have for you off the top of my head. 🙂
Yes, the carrier is suppressed at the transmitter. The sidebands remain without the carrier (the carrier is suppressed by means of the functionality of the balance modulator). The sidebands exist at the transmit frequency (as you can see in the image on the spectrum analyzer) and are expelled into the air by the same means as the carrier would have been. Thus, the only part of the signal that is transmitted are the sidebands. In the case of SSB, the single sideband. 🙂
Excellent presentation. For the local oscillator feeding into the product detector, what frequency do you use? What considerations go into that choice?
Well, my friend, in this case the balanced mixer I used operates at 455 KHz, so the RF source has to be 455 KHz. It is a fixed frequency source. The signal then goes into a 455 KHz IF which feeds another mixer. This is where the variable frequency local oscillator comes into play. One the other side of the coin, the product detector. Again, this chip, when used as a product detector, is expecting 455 KHz. It uses a fixed frequency source and the I.F. coming from the I.F. chain at 455 KHz. Ahead of the I.F. chain is the mixer responsible for taking the R.F. and down shifting it to 455 KHz. The local oscillator feeding this mixer would have to be set to a frequency that is 455 KHz off of the receive frequency to do this. This mixer is followed by the I.F. chain which consists of amplifiers and filters so the anticipated artifacts of the mixer do not make it to the detector. Hope this helps
@@eie_for_you It does indeed help. Thank you. The only thing I'm curious about now is it sounds like the 455KHz must be some established standard. Otherwise it sounds like the source station could be modulated with 455 and if no standard then a receiving station could be using something else entirely. Or, am I missing something related to this xmt/rcv situation....? Thanks.
@@NickFrom1228 Yup, 455 KHz is a very standard I.F. frequency that has been in use for a very, very, VERY long time. It is not the only standard, however, but it is probably the oldest. It was chosen so as to avoid a bunch of artifacts associated with mixers that cause problems downstream. From the receive perspective, it really doesn't matter what the I.F. frequency of the transmit station was as long as we add in a carrier at our I.F. frequency at the receiving end.
Dear gentleman, I would be pleasured if you can answer to my follow question. If I have a theoretical periodic and perfect-shape sine wave, what I can see on the spectrum analyzer? I expect to find a single frequency, isn't it? No any harmonic. Thank you for spend time to answer me.
If you have a perfect sine wave and your mixer/modulator does not contain any non-linear characteristics, then you will see one pip at the modulation frequency on either side of the carrier frequency (DSB).
@@eie_for_you Thank you for your answer, gentleman. I meant a pure signal, not a modulating signal over a carrier. In my case, again, will I see only one vertical line on the spectrum analyzer, correspondig to that sisgnal? (I'm trying to find out a book, but all books (signal & systems) have an heavy mathematical base which I would like to overlook, looking for the practical conclusions. I would be grateful to you if you can suggest me this kind of document/book, a sort of "signal & system for dummies", that can explain the real examples of modulated signals emitted by a radio and how we can see these on a time domain and frequency domain. Thank you very much indeed again. 73 de IZ7VHF.
@@RobertoPietrafesa No modulation of any kind - a single pip on the screen which is the signal in question. Here is an interesting read to parse out around the math: drive.google.com/file/d/1AvVF_RyaYbevQHYDLhYaxsXs8IWPQy9o/view?usp=sharing
@@eie_for_you Thank you Mr Ralph for this suggestion! I will read it deeply and soon. Clark Gable is to american actors as Ralph Gable is to youtube trainers! 🤩
@@RobertoPietrafesa There is also these four videos that might be helpful: ruclips.net/video/vlIINDI0joE/видео.html and ruclips.net/video/TaR8AYGjqv0/видео.html and ruclips.net/video/pM3WZqfC6Sc/видео.html and, lastly ... ruclips.net/video/gPUqWXEWI94/видео.html
Hello, I study electronics and radio communication for my own so I have nobody to ask my question and in books it is explained similar to your video but I still don't get it. Let's say I want to create AM signal with carrier wave 100 000 Hz and I want also to transmitt my stable (and very boring) audio signal 1000 Hz and what I don't get from where do I have other frequencies than my carrier 100kHz and signal 1KHz ??? I use my oscilloscope and I see this beautiful shape of AM modulation , I see my carrier and waves higher and lower in voltages which creates all of this and my signal formed by this carrier 1 kHz but where do those 3 kHz etc. come from? Where can I find sidebands looking at my oscilloscope (I know it is a little bit childish question but I don't know how to explain it).
The additional sideband signals that we see are from harmonic distortion in the modulated signal. If we had a pure, perfect 1 KHz tone (without any harmonic distortion in it) and a perfect modulator, then we would only see the single 1 KHz sideband pip. But, alas, nothing is perfect. So we get this additional "stuff." The only way to see it is using a frequency domain device like a spectrum analyzer or an oscilloscope with FFT capability. Hope this helps dispel the fog a bit.
@@eie_for_you Thank you for the answer! I see now. So If I had a lot of distortion I would have a lot of other frequencies on spectrum analyser? Or it is the case also when I can hear my 27 MHz singal on my radio tuned to 2,7 MHz ? So it is like a bad copy of my oryginal singal in different frequencies? I am trying to understand this. I always discover something strange which doesn't follow the explanation from the book.. I know that the examplaes are ideal examples but still some authors can't explain simple things or maybe they can't ...
@@grzesiek1x Yes. The more distortion, the more frequencies you would see on the spectrum analyzer. You could have some Excel fun with this... An AM signal has the equation v(t) = (1+sin(2*pi*fmod*t))*cos(2*pi*fcarrier*t) where fmodulation is the frequency of the modulation, fcarrier is the frequency of the carrier, t is time in seconds. This assumes a sine wave modulating the carrier. Excel will do an FFT. You use this equation to generate the time domain signal, use Excel to do the FFT to get the frequency domain stuff.
May I try to add some basic explanation for you ? It is some understanding that got to me recently, so I am glad to show it. Have you ever tuned an instrument with a tuning fork ? Lets say a guitar, and the snare to be tuned is slightly off. When you strike the snare and fork at the same time, you will hear 4 things: the frequency of the fork, the frequency of the snare, AND the difference between these two, AND the addition of the two, often less noticeable. When the fork is 880 Hz, and the snare is tuned as 882 Hz, you will also hear the 2 Hz difference as a wining extra sound. And there's also the total (addition) of the two basic tones, 880+882=1762 Hz, less noticeable than the 2 Hz. In this story, the 2 Hz and the 1762 are side bands, extra wave energy left and right of the two main frequencies of 880 and 882 Hz. By the same principle two extra energy bands form when you take a carrier, and ADD a modulation on it. The guitar example were low frequencies, and the difference was small (2 Hz), while the addition was large (1758 Hz) compared with the ground frequency of 880 Hz. But if you use an example of 10 MHz with a modulation of 1KHz, the subtraction is 9.999.000 Hz and the addition is 10.001.000 Hz. Two extra frequencies are formed, the side bands, with the carrier in the middle. When you would not use 1000 Hz modulation, but spoken word, a whole spectrum is formed as side bands close to the carrier. I think it is not possible to see these bands on a normal scope, because they linger to close to the carrier frequency. That is why they use a spectrum analyser, so you can see how the different frequency energies are distributed around the main frequency.
@@MrStickyPete Sorry to break the news to you, but ... nope. I'm looking at the time domain trace of a single tone modulated SSB signal and it looks no different than the DSB. I check my ARRL radio amateurs handbook, same story. 🙂
Thank you. I am a teacher just beginning to explore radio for various student projects and this was the first video I came across that showed how the process of carrier removal and side band halving worked to be turned into the original signal that I could readily follow and see the changes to the waveforms. Well done and thank you again for the clear explanation.
You are very welcome! If you have any other questions, please be sure to let me know. They might even generate another video or two or three! 🙂
This video gets an A+ for clear education. This has been the most helpful explanation of SSB signal vs AM. Thank you.
Thanks, man!
You get an E- for punctuation
The quality of your channel is rare. Very well produced videos. Subscribed!
Thank you for the encouragement! Welcome to the "family"! :-)
Thank you. What a brilliant explanation!
You are welcome and thank you! 🙂
What a great video! Thank you!
Thanks! I'm so glad that you found this helpful. You are very welcome!
Thank you for presenting a rational explanation of single-sideband signals that does not require an understanding of calculus.
The signals produced by a balanced mixer aren't quite what you describe. They are in fact, F1, F2, F1+F2, and F1-F2, for carrier and modulation frequencies of F1 and F2, respectively. There are no F1+F2*2, F1+F2*3, and so on. The reason you see those frequencies on the spectrum analyzer is due to two things: harmonic distortion in the modulating signal, and nonlinearities in the modulator and stages of RF amplification after the modulator. In your first example at 4:51, you can see that the F2*2 (and its opposite sideband) components are 20 dB below the F2 signal. This is what you should expect to see if your signal generator has just 1% harmonic distortion. But as I said, nonlinearities in the RF path will also cause these sideband components to increase. You mentioned later (11:04) that you were surprised to see odd harmonics but not even harmonics of the modulating frequency in your SSB signal. This is related to they type of distortion in your modulating signal, or the type of nonlinearity in your RF path. Since I assume you're using the same 1 kHz source for both examples, my guess is that the additional signals are being produced mainly by RF nonlinearity. A clue to this is that what you are seeing are only odd harmonics. As you probably know, square waves contain only odd harmonics. So any kind of nonlinearity that behaves like a square wave is likely to show domination by odd harmonics. In practice, "acting like square waves" is what happens when both peaks of your RF signal are being clipped or limited. It is this symmetrical limiting that is the most common nonlinearity in RF amplifiers, and also the reason you see mostly odd harmonics of the modulating frequency in an SSB RF signal.
I will also pick a nit with your statement that double-sideband wastes power. It DOES waste spectrum, exactly as you describe, but what I have noticed, using software-defined radio to listen into shortwave broadcasts, is that if you use SSB demodulation to detect an AM signal, you get a lower signal-to-noise ratio than you do when using a DSB demodulator. If you think about that for a moment, the reason becomes clear: by having energy in both sidebands, you are detecting twice as much energy for the same amplitude of signal, just because the DSB detector sums those energies together. So to get the same signal level from an SSB signal, you actually need twice as much energy in that one sideband. You might ask, doesn't the noise also get doubled as well, since your receiver bandwidth is twice as wide? The answer requires more math than I am prepared to present right here, but the noise in a receiver does not increase linearly with bandwidth, but as the square root of the bandwidth. So by using a double-sideband demodulator, you increase the sideband energy by 2, but the noise level by only 1.4 (square root of 2). So in practice, the much more significant advantage of SSB is about bandwidth conservation rather than power conservation.
Thank you again.
First, with regard to the observed harmonics. Yes, IF we had a perfectly linear modulator (mixer) and perfectly pure signals to mix, we would have simply F1 +/- F2. However, as you rightly point out (and I mention in the text contained in the video description), we do not have either of these. So, in a real world mixer and with real world signals, we do, indeed, have all of these harmonics to deal with. 😞
Now, with regard to the whole "wasting power" issue. My point was that we are putting power into either redundant "information" or something that does not actively carry information, not that SSB uses less power. If I am transmitting with 100 watts, that power is spread across the entire bandwidth of my transmitted signal. This would include the carrier, if I am using AM. However, if I am using SSB, then this 100 watts is "concentrated" only in the single sideband which contains everything I need. So, in terms of DSB vs SSB, the power density of SSB is twice that of DSB IF I am transmitting with 100 watts in both cases.
So, yes, bandwidth conservation ... absolutely. Again, this means that all of my power goes into the information I am looking to communicate. I am not conserving power, but concentrating my power in a single sideband.
Unfortunately, YT does not allow its creators to simply "replace" and existing video or I would refactor this one adding these explanations to it. I can either totally delete the original video with all of its history and the like or I can add a followup video.
Unfortunately, few people actually read the description for the additional explanations.
So, I suppose that a followup video is in order. I can place a link in the existing video to the followup.
I do not know when I will get to it, but I am going to put this in the video queue.
@@eie_for_you I do get it - sorry I didn't see that. What some people do is put any additional explanations/clarifications in the comments, and pin it to be the top comment.
@@BrightBlueJim That is certainly a good idea. It would get more visibility that way.
Concur with one additional note: The 2 KHz spacing on the spectrum analyzer suggests IMD, intermodulation distortion, the two sidebands are spaced 2 KHz apart and are probably modulating each other after the output of the modulator; a non-linearity in the buffer amplifier. Many IC amplifiers use a totem-pole arrangement of the output transistors in order to have a bipolar output (with positive and negative voltage swings) and a nonlinearity is essentially unavoidable at the crossover. A simple single-ended buffer stage using a highly linear device (JFET perhaps) and capacitor output would likely remove most of these IMD sidebands.
Love your videos!
Thanks! 🙂
Excellent useful lecture. Greatly appreciated.
Thank you and you are very welcome! 🙂
Very very good video thank you for actually showing and explaining clearly WTF is going on. Every reference I've seen until now just says something useless like "Oh they're duplicated so we can just throw them away". Ok but you cant transmit without the carrier soooooo, thank you for clearing all that up real well. No I understand you can transmit anything and it's about how we modulate in balanced vs unbalanced mixers. Next up to research how the actual maths of those mixers work. How come "balanced" manages to squash the carrier to 0? etc.
Thanks again!
Thank you! The most common hardware-type balanced mixer these days is the Gilbert-Cell which actually has a LOT more uses than just a balanced mixer. It s composed of three difference amplifiers. Two of these are cross coupled with the RF being connected to this input. Because they are cross coupled, the one difference amplifier "fights" the other difference amplifier. The resulting output is ... nothing.
The third difference amplifier individually controls the current that is allowed to flow through the other two. Remember, the difference amplifier has a bipolar output (Vout+ and Vout-). The audio signal is fed into this third difference amplifier. The balance that maintains the zero output of the other two difference amplifiers is disturbed at the rate of the audio to this third difference amplifier. Thus, the only time that there is an output from the other two difference amplifiers is when there is an audio signal applied to the third. This output, then, varies in amplitude with the amplitude and frequency of the audio signal.
I do plan on having a video on this subject. It in my videos to be done queue. 🙂
Excellent!
Thank you! 🙂
Imagine Oil Barrel That You Need To Send, The Packing matterial, Boxes, Padding, It Will be Really 4 Times The Size And Weight of It At The End, Now Imagien If You Could Fold The barrel In Two, Imagine Cutting The Barrel In Two, Now You Can Lay In The Other Side Of Other Side Of The Barrel And When You need To Use It Just Unpackc It And Weld It Together, Thats What The SSB Signal Is, Usb Or Lsb, The Unpacking Is DOne By A Program / Modulation, It Unfolds The Barrel Everytime You Need It, But To get A Seal On it You need To Weld It , In Radio Case That Welding And Cutting is Done By A Programs, Low Pass Filter,Band Pass Filters And Other Kind Of Filtering Systems Or Circuit That Is Designed To Do Just That.
Frequency Watchers Here, Greetings To Whoever Found This COmment Usefull.
Interesting analogy
I’d really appreciate a video that covers the circuit theory around the balanced modulator. This video covers a high level overview but not a lot of the electrical engineering around component selection. A good video for its intended purpose.
Yes, it was a high level overview of the mixer itself. I used a "ready made" mixer that exists inside the IC. There is actually several ways that this balanced mixer is implemented, so the discussion can get a bit complicated if we were to cover all of the options. Probably one of the most common implementations used today is the "Gilbert Cell" which consists of a "matrix" of matched transistors and a small number of resistors. I could have a video on this one implementation easily enough. I will add it to my list of videos to produce. In the meanwhile, to satisfy at least some of your curiosity, you can find it here:
eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Microwave_and_RF_Design_IV%3A_Modules_(Steer)/06%3A_Mixer_and_Source_Modules/6.03%3A_Single-Ended_Balanced_and_Double_Balanced_Mixers
and here:
rfic.eecs.berkeley.edu/~niknejad/ee142_fa05lects/pdf/lect18.pdf
Hope this helps.
Your comment got my curiosity up and just **HAD** to play a bit. I created a Gilbert Cell balanced mixer using LTSpice (FREE circuit simulation program). Here is a link to my model:
drive.google.com/file/d/1CAEdY_aOMJJHIAjicFtPyRCJHNRR45zj/view?usp=sharing
It is by no means a perfect design example. I was just thrashing and playing. It was fun and a nice precursor to when I make my video on the subject.
Here's the download link for LTSpice:
www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html
A lovely explanation, thank you-as a ‘returnee’ to Ham radio after 40 odd years, I need the cobwebs blowing away. All the info is in there..somewhere. This helped bring some of it back!
I am so glad that you found it helpful! 🙂BTW, the extra sidebands beyond the 1 KHz are from harmonic distortion in the audio and non-linearities in the balanced mixer. 🙂
Thanks for including Bible right in the channel.
You are very welcome, my friend! 🙂
Great video!
Thanks! And there is a followup coming up very soon which explains the extra sideband content. 🙂
One of the earlier attempts to use the radio spectrum more efficiently. Now we have ctcss and other tones to help. Also trunking systems and other digital communication systems.
Interesting thought. However, we are talking two different things here. SSB is mainly used in HF communications. CTCSS and so on are used with FM modulated signals in the VHF and up range. So, yes, the systems you speak of DO save spectrum space but do not apply to HF. 🙂
This Video Is GOLD, A GOLD I Say, BUT This Video Could Be In 10 Minute Form Easily ! :) But Thank You Anyway, People WHo Are Interested In Radios Will Apriociate Your Video :")
Thanks! 🙂
Great, short and clear. Of course, not in depth, but just to get me curious to find out more 😀
Thanks! 🙂
Yup! There is only so deep one can go in a video this short. I **DO** plan on a video on the Gilbert Cell balanced mixer. It is actually very much in the works. But, admittedly, it will be a few weeks before I get to it.🤓
@@eie_for_you Keep up the good work ! Appreciated.
@@ernestb.2377 Thanks! 🙂
11:30 The presence of harmonics of the modulating frequency is a defect or deficiency; nearly impossible to avoid but not really part of the balanced modulator process. The more linear the modulator the more perfectly the presence of a pure sinewave modulation will produce exactly one upper sideband and one lower sideband frequency peak. These sidebands can modulate *each other* and since they are 2 KHz apart, that is where your 2 KHz harmonics are appearing, a phenomenon called IMD, InterModulation Distortion. As you can see, these IMD sidebands greatly exceed the expected transmission bandwidth.
The absence of 1 KHz sidebands tells me the balanced modulator is highly linear and effective; but the IMD sidebands tells me the buffer amplifier that follows is not perfectly linear and is allowing the upper and lower sidebands to modulate each other.
This is also the main difference between one of your top name-brand radios and cheap radios; is how well they resist IMD during receive and avoid it on transmit.
Very true! And, unfortunately, this was a realization which occurred *after* the video was posted and it had a lot of history.
I added additional text to the description to this effect.
Unfortunately, YT does not allow me to update any given video with a new video. Otherwise, I would have made this note to an updated video. I can only release a completely new video and totally delete the old one, losing ALL of the history (and benefits) of the old one. 😞
Again, a very informative video on not-so-simple topics. Thanks for that!
You are very welcome! I am glad that you found it helpful! 🙂
Very clear explanation, my friend! Thank you for the time you spent to create this video for the community! Subscribed. Best wishes from southern Italy de IZ7VHF !
You are very welcome! 🙂 I am glad that you found it beneficial.
@@eie_for_you I add: you also seem to be a good and selfless man, the ideal person with whom I would have liked to have a good glass of wine in the evening, after dinner, to chat about philosophical questions. Have a good luck, my friend, you and the people you care about.
@@RobertoPietrafesa Thank you Roberto. I think I would like that, too! 🙂
Nice Job Ralph, love your videos!
Thank you for the encouragement! :-)
Simply amazing explaination of SSB and easy to comprehend! I am now subscribed.
Thank you and welcome to the "family"! I am so glad that it was helpful.
It is evident that you put a great deal of attention, thought and effort into your presentation. And it was a comprehensive refresher that I really enjoyed.
There is one question I have about SSB that I've never found a satisfying answer. And tonight I just re-created the experiment that illustrates my question:
Transmitting with a FT 747-GX into a dummy load and listening on an Icom 7300 (with headphones) on 80 meters I transmitted my voice in AM and SSB.
Comparing the two, AM has a noticeably higher audio quality. It sounds more rich, and I would not be surprised if more of the audio spectrum is being "captured" and "transported" on AM.
We know AM is about double the bandwidth of SSB modulation. But, as your video explains, each sideband in traditional AM is a mirror duplicate. And in AM, if I'm not mistaken, the detector diode of a basic receiver only cares about one of the sidebands.
For the human audio spectrum: 20hz - 20khz; it seems to me going from 3khz up to 6khz is a bit of a wider of a slice of it. But I'm not convinced it's the increased bandwidth that explains the better audio quality.
Is it this, or something else?
Thank you.
Really good question ... made me revisit something.
If you remember from the video I observed that the double sideband suppressed carrier signal was missing its even harmonic sideband components. I saw only the odd ones at 1 KHz, 3 KHz and so on. I questioned within myself if this was just because of my homebrew balanced modulator. So, I repeated the experiment with my IC-7610. I saw the same thing and then some.
So, besides the fact of the phase distortion and narrower audio bandwidth that I mentioned in the video, there is the fact that we lose sideband content. In the case of the IC-7610, there was ONLY the 1KHz sideband whereas AM had 1, 2, 3 and 4 KHz sidebands.
I saved the data from my IC-7610 experiment in a spreadsheet and put it into a ZIP file. Here is the link to that zip file:
drive.google.com/file/d/1eNx9kYhcokmrtD3wYco1Z4nT0EYcaZDr/view?usp=sharing
I hope this satisfies your curiosity.
Hey Benjamin ... I did a deep dive into this whole question and the spectral content of an AM signal and all. I even worked through a mathematical model of AM and did an FFT of the resulting time domain signal.
It turns out that the **IDEAL** AM signal will have the carrier with a single pip on either side of the carrier (sidebands). The extra pips at 2xFm, 3xFm, etc represent distortion in the signal. So, it looks like we are left with the audio bandwidth at both the transmitting and receiving end as well as the phase distortion that I originally spoke of in the video.
@@eie_for_you Thanks for the insightful replies and crunching the numbers. I postulate in SSB the lack of fidelity is primarily caused by phase distortion and the audio bandwidth issue is negligible.
One way to find out: What if we somehow restricted an incoming baseband audio signal to 3khz going to an amateur transceiver transmitting in AM. And compare this control group to SSB with the spectrum analyzer hooked up to the output of the receiver.
No I'm no EE, so I can't back it up with all the math, but what I suspect causes the phase distortion is the reinsertion of the carrier at the receiver. Even if the carrier is reinserted at exactly the right frequency it is no longer in phase.
One further reason I suspect it is the phase distortion is: doesn't commercial FM broadcast stereo employ double sideband suppressed carrier? What is the phase reference? I bet it is the pilot tone!
Thanks again!
@@margaqrt FM broadcast is Frequency Modulation which, by definition, continuously transmits a carrier plus sidebands on either side of that carrier. I am not sure all of what makes up a Stereo FM Broadcast signal (never paid any attention to it), but it is still FM. The mathematical equation for FM is **FAR** more complex than AM. It almost hurts to think of it. LOL ;-)
Isn’t it also a matter of filter bandwith? On some radios you have the possibility to select the filter regardless of the type of modulation. By doing that effectively you can experience a narrow AM with the “closed” sound to it or a wide and bright SSB audio signal.
Thanks for this interesting analysis supported by intuitive examples.
Very good explanation!
Thanks! 🙂
That was a very good explanation of the basics one needs to know!
Thank you for that! Thumbs up and subscribed…
Regards from Germany 🇩🇪
Thank you! I am very glad that you found it helpful! 🙂
Brilliantly clear video. Earned a subscriber!
Thank you so much! I am so glad you appreciated the video. 🙂
Thanks for the video!
You are very welcome! :-)
I just added a link to a ZIP file which has an Excel spreadsheet in it comparing the spectral content of AM, LSB and USB using my IC-7610 in the video description. Here is the link for your convenience if you are interested:
drive.google.com/file/d/1eNx9kYhcokmrtD3wYco1Z4nT0EYcaZDr/view?usp=sharing
Thank you for John 3.16 and for Ainos (0:49 - Ainoses were a NATION, not a tribe, in Japan and eastern Asia - nationalized finally by Japaneese. I came here looking for ssb information - i am not even a licenced radio operator :)
You are very welcome on both counts! 🙂Admittedly, I honestly was at a loss for the Ainos reference until I went back to view the video to discover what you were referring to. This was a picture that I downloaded from PIXABAY as an illustration of oldness.
Thanks to you, I learned something today! So, thank you! 🙂
This video gave me ideas. Thanks for sharing!
You are so welcome! :-)
You Remind Me That Turrtle From One Clip, Good Quality Video, Top Noch !
Thank you! :-)
Thanks Elmer!
You are very welcome! 🙂
Cool. Found this for my General Class 12 and 15 yr daughters. John 3:16. 👍
Praise the Lord that it was helpful and ... WOW! General class at 12! I got my Novice at 15 and General at 16 back in 1971.🙂
@@eie_for_you she was actually 11, but she really worked hard for it.
@@halledwardb WOW! One smart cookie! 🙂
Great vid. I understand time domain displays on o-scopes with the HF carrier being shaped by the Base frequency forming the "envelope". What I can't wrap my head around is how does the audio/base "envelope" frequency show up as sidebands on either side of the carrier on spectrum displays. Say, the carrier frequency is 7Mhz - why/how does the base/audio (say 1khz) show up as 7.001Mhz and 6.999 spikes either side? 1khz is way, way below 7Mhz and has no business being there either side of the 7Mhz carrier in my mind.. lol
Gooooood question! Hang on for the answer, because to explain where the sidebands come in, we have to dive into the math to see it. Remember that I said that a modulator is a “multiplier?”
Step 1: Our RF is sinusoidal. So we can write the following for the carrier in the time domain:
v(t)=Ac*cos(ωc*t)
Where Ac is the amplitude of the carrier, ωc is the frequency of the carrier in radians-per-second and t is the time.
Step 2: Now we have our modulating signal. We can write a similar equation for the modulating signal:
m(t)=M*cos(ωm*t)
where M is the amplitude of the modulating signal, ωm is the frequency of the modulating signal in radians-per-second and t is time.
Step 3: We modulate! The mathematical equation for Amplitude Modulation will be
Vm(t)=Ac*cos(ωc*t)+(M*cos(ωm*t))*cos(ωc*t)
Looking at this last portion a little bit, we have the amplitude of the modulating signal times the modulating signal itself times the carrier signal.
Now, I pull out the CRC Math tables to find that
cos(A) * cos(B) = ½*cos(A-B) + ½*cos(A+B)
So, for this last bit of the modulation equation I will set A = ωc*t and B= ωm*t so we get:
M*(½*cos(ωc*t - ωm*t) + ½*cos(ωc*t + ωm*t))
= M*(cos((ωc - ωm)*t) + cos((ωc + ωm)*t))/2
Notice the (ωc - ωm) and the (ωc + ωm)! The carrier frequency MINUS the modulating frequency and the carrier frequency PLUS the modulating frequency.
The complete equation now looks like this:
Vm(t)={Ac*cos(ωc*t)} + {M*(cos((ωc - ωm)*t) + cos((ωc + ωm)*t))/2}
Vm(t)={Carrier} + {Sidebands}
The first part of the equation is the carrier. The second part of the equation are the sidebands.
You can try this in EXCEL (I just did for fun using 250KHz for a carrier and 1 KHz for the modulating signal) and, when you plot a graph of the results, you will see an amplitude modulated signal.
At this point, I either blew more fog into the situation or I burned off some of it. Hope it is the latter of the two. 🙂
@@eie_for_you I'll come back to you on that :)
You and I, and many others, struggle with the same thing. It starts out with “here is the amplitude variation on the oscilloscope” and immediate jumps to “the carrier amplitude is constant and there are the sidebands” on the analyzer.
I believe sidebands aren’t real, they only exist because of the analyzer math.
@@nohrtillman8734 I'd politely challenge your disbelief in sidebands being other than a mathematical curiousity by merely stating that analogue SSB radios exist. 😃
@@DennisSantos Pehaps it has been a 70 year old marketing ploy, and that SSB switch really doesn’t do anything. 🙂
👍
Great video! Subscribed.
Welcome to the "family!"
Noce prezentation. One of the bigest problem with single sidband recepion is signal phase distortion as propation delay can not be restor by injeting carrier that is not effeted by that.
I wonder if pilot signal could be injected to voice sinal (simulat like stereo pilot in FM), so it will still show as SSB (not carrer). Once the signal is demodulated the pilot singnal coul be used are refrence to correct any phase distortion.
Thanks! Now that is an interesting thought. You should give it a try and see how it works. :-)
@@eie_for_you Well I did not know that , but such modulation standard exist. One of them is ACSB (Amplitude-Compounded Single-Sideband Modulation)
One of your static display screens was broadcasting white noise.
Actually, if you look closely, there are sidebands there for double sideband, suppressed carrier spectrum. The problem is that the line is light blue and hard to see.
The video is good, but you didn't do what no one else does either: Graphically display the difference between USB and LSB on the oscilloscope.
I'm glad that you enjoyed the video. :-)
Well, the reason why no one shows the difference between LSB and USB on the oscilloscope is because there is no difference between LSB and USB as viewed on the oscilloscope. Where the difference is observed in with a spectrum analyzer (frequency domain). Here we can see the LSB envelope below the carrier frequency and the USB envelope above the carrier frequency. In the time domain, there is no difference between the two.
@@eie_for_you Thanks.
@@cosmefulanito5933 🙂 You are welcome
When you listen adults speak on the old Peanuts tv specials, it always sounded to me like SSB without a beat frequency present. I always wondered if that’s what they did to create that distortion.
Playing devils advocate to jump start my brain into understanding this AM frequency shift thing.
Oscilloscope = real time representation of a signal.
Frequency Analyzer = math applied to the time domain.
Does it stand to reason that sidebands only exist because of the Fourier math applied to the real time domain capture?
5:14 a “pip” is a small hard seed
Maybe you meant to say “peak”?
Probably a better term ... but you got the point. 🙂
I liked the video, but am wondering why the frequency domain has multiple peaks beyond the first upper and lower sidebands at 455 +1 and 455-1. Where do the other smaller peaks come from if the audio signal is a pure 1 kHz sine wave. ??
Good question! And, at the time I created the video, I was not remembering some stuff.
Those are due to harmonic distortion of the audio and/or the non-linearity of the balanced mixer used to produce the modulated signal. If we had an absolutely pure sine wave and an absolutely, perfectly linear mixer, then there would only be sidebands at 1 KHz either side of the carrier frequency.
I made a note of this in the video's description. RUclips doesn't let me "fix" an existing video. 😞
Hope this helps. 🙂
Hello sir, i have a modern radio (XHDATA D808) which has SSB Fine tuning (USB & LSB) functionality, many people say that modern radios doesn't have BFO but how's it possible to recover original signal without re-injecting the carrier signal ?
Yes, the glories of digital signal processing (DSP). They suck the digital samples of the SSB signal into a processor and digitally reproduce the original audio. I am not sure how they do that as I am *definitely NOT* a DSP guy, but they can do amazing things with sampled data.
@@eie_for_you oh ..... Thank you so much for clearing my doubt 😀👍🏻
It isn't and they do. That is to say, the original carrier frequency is mixed with the incoming RF, and this exactly reverses the operation of the double balanced mixer. This can be done digitally by multiplying the samples of RF with samples of the carrier frequency. Since the incoming frequency might be 7.101 and the sampled carrier is 7.100, what will happen is the output of the multiplication will slowly vary in amplitude and this varying will be exactly 1 KHz, the recovered audio frequency. In other words, for a while the samples of RF and the samples of carrier will strengthen ( 2 * 2 = 4) and 1/2 millisecond later they oppose ( -2 * 2 = -4) and midway between these points the math produces zero: ( 0 * 2 = 0).
So, analog in a Double Balanced Mixer or digitally in a DSP, works the same way.
You forgot to talk about the Beat Frequency Oscillator :-)
Well ... I kinda did. I just didn't call it that (though I probably should have). I talked about how the carrier had to be added back in. This was the job of the Beat Frequency Oscillator. It was a bit difficult to use (I did that on my first receiver, a Hallicrafters SW-25), but it could be done.
Modulation: Is to add some intelligence to a radio signal. (This definition obviously said by someone who hasn't listened to the bands lately)
LOL!!!🤣 (sad, though)
Watching your SSB video a question dawned on me. You say the unbalanced modulator produces AM or F1+/- nxF2, meaning harmonics of lower frequencies of the modulating audio end up in the final AM signal. Just as your specan display of 455kHz modulated by 1kHz produced the carrier along with +/- 1Khz, +/- 2kHz, +/-3kHz etc.
Does an AM envelope detector remove the additional modulating tones (+/- 2kHz, +/-3kHz etc) or are these extra tones end up as harmonic distortion at the receiver?
Same goes with your homemade Balance Modulator that only produced odd harmonics of the 1kHz modulating tone.
Can the SSB receiver's product detector remove the "in band" odd harmonics or is harmonic generation (distortion) of low band modulating frequencies integral with all forms of AM?
Actually ... as noted in the video description ... the **ideal** AM modulated signal and DSB modulated signal will only have a single sideband on either side of the carrier frequency.
These extra sidebands that we are seeing here represent harmonic distortion that is introduced either with the audio signal source or the modulator itself. 😲
The *ideal* demodulator will faithfully reproduce the audio found on the RF signal, harmonic distortion and all. Reality is, the demodulator itself may also introduce its own harmonic distortion. 🙂
My compliments on your excellent video. I have a question that I feel I should know the answer to. Given the structure of an ssb signal, it seems that as I slowly increase the frequency while listening to a usb signal, the pitch of the voice I'm hearing should slowly increase. Instead, the opposite occurs. Would you please explain why? Thank you.
Good question!
Think of it this way ... the frequency of the audio that you hear is relative to the position of the carrier. When you change the frequency that you are listening to, you are changing the position of that carrier while the sidband signal has not moved.
Let's say that you are listening to USB. If the carrier is positioned in its original location, then all of the sideband signal is above the carrier position.
As you tune up in frequency, you are increasing the frequency of the injected carrier which is moving it closer to the unmoving sideband signal. Its *relative* position is closer and, thus, the audio frequency goes down.
Hope this helps dispel the mystery. 🙂
Thank you very much - this has been bugging me. One follow-up if you don't mind - the "injected carrier" you reference is injected by the receiver, correct? @@eie_for_you
@@rick2194 Yes, that is correct. It is the one that is required in order to "make sense" of the SSB signal being received.
If your modulating frequency is a pure sin wave why do you get so many extra bands in frequency domain? Great video tho thanks.
Good observation! Yes, this is harmonic distortion which exists either because of an imperfect audio source or an imperfect modulator or both.
The AM signal was generated using my Rigol Signal Generator and its internal audio source.
The DSB signal was generated using the modulator I built and the audio source is my Tenma signal generator.
I have not pursued trying to figure out where the fault lay yet. 🙂
I’m going to ask what may be a possibly dumb question, why doesn’t 2m and 70 cm just operate Single Side Band instead of FM? I feel like this would be a more efficient use of frequency allocation and energy
That is a good question. One which I have no answer for. Of course, FM isn't subject to interference (noise sources like static) like SSB is.
Your question is not dumb. Most of my experience was with 2m, so that informs my comments. The band covers 144- 148 MHz, which is a large piece of spectrum that has never been very crowded compared to the HF bands. Large portions of 2m have never been regularly utilized, so any transmission mode would not be an issue with respect to spectrum crowding. Since most communication on VHF and UHF bands is line of sight, NBFM produces a higher quality received signal in mobile and portable operation. Equipment, both transmit and receive, is relatively simple to implement (compared to SSB) and small vertical antennas work well when communication takes place through a repeater. On the other hand, DX is possible on 2m when certain atmospheric conditions are present or when bouncing signals off the moon or Aurora Borealis. In those circumstances, CW and to a limited extent SSB are superior.
I got my ham license in the early 60s while I was in 9th grade. I was interested in the technical aspect of the hobby and not very keen on CW. With a Technician license, I could operate phone on 2m and that's where I started with a Heathkit Twoer (lunchbox) AM transceiver. It only put out about 1 watt and had a super regenerative receiver which wasn't very good (broad as a barn and deaf to all but the strongest signals). As time went on, I bought brand new Army surplus ARC5 receiver for $15 and built a 6CW4 nuvistor converter. Now I could hear a lot better, but nobody could hear me. Thanks to another local ham and great army surplus parts availability, I built a linear power amplifier from a donated 829B tube. I used the twoer to drive it and started increasing my reach to stations further away. Soon I noticed SSB activity and wanted to contact those stations as well. I found an article in CQ magazine that described how to build a 6m SSB transmitter. I scrounged enough parts to put it together, but needed a way to get it on 2 meters. QST published an article on how to build a 6m to 2m transmitting converter, so I built it. Soon I was on 2m SSB with about 60 watts from the 829B linear and was making contacts deep into Ohio, Ontario and western NY (I'm in Michigan). I was hearing stations running more power but they couldn't hear me. By now I was a senior in high school and when I graduated, my parents gave me a 60' tower as a graduation present. My dad and I erected it and put an 8 element beam on top. I still needed more power and started gathering parts to build a linear amp based on a pair of Eimac 4CX250Bs. I met a lot of great hams locally, and one gave me a pair of used tubes which made it possible for me to finish the amp. I worked 13 states on 2m SSB with some of them via the Aurora (point the antenna north and listen for ghostly CW signals or SSB that sound like whispers). College and other interests displaced my ham radio days and I gave all of my equipment away. After I left home, my dad sold the tower. I never got bitten by the 2m NBFM and repeater bug, but my senior design project in college was to design and build a 2M NBFM transceiver which sits on the shelf today. I think 2m NBFM killed a lot of the potential for 2m SSB, kind of like MTV killed the radio DJ!
If your mixer / modulator were clean, you wouldn't have pips at the harmonics away from the carrier, only the fundamental. You're getting those harmonic pips because your modulator is distorted creating harmonic products.
You are absolutely correct! :-) I discovered this fact AFTER I posted the video and added comments to this effect in the description. Thank you for pointing that out. Always learning we are!
Hi Ralph, nice video. it’s not immediately obvious to me why the unbalanced mixer takes F1 and F2 as inputs but puts out all of those n*F2 harmonics. Anything on that?
A good question ... and you are not the first to ask.
The answer is two-fold.
First, there could be some harmonic distortion in the modulating audio.
Second, there could be some non-linearity in the mixer itself.
Being that the AM and the DSB use different audio sources and the modulation is being accomplished with two different mixers, this would explain the difference in the harmonic content of the spectrum.
Hope this helps.🙂
@@eie_for_you it’s not intuitive yet but at least there’s an answer… I’ll work on backfilling the technical background. Thanks!
@@DaylightRobberyCA The thing to remember ... we are not talking D.C. here. We have to remind ourselves that we are talking R.F. and capacitance and inductance and so on. As such, the coax is part of the circuit "components" that make this up. That's all I have for you off the top of my head. 🙂
But, how are those sidebands transmitted without the carrier? If the carrier disappears - no sidebands?? Is the carrier suppressed at the transmitter?
Yes, the carrier is suppressed at the transmitter. The sidebands remain without the carrier (the carrier is suppressed by means of the functionality of the balance modulator). The sidebands exist at the transmit frequency (as you can see in the image on the spectrum analyzer) and are expelled into the air by the same means as the carrier would have been. Thus, the only part of the signal that is transmitted are the sidebands. In the case of SSB, the single sideband. 🙂
Excellent presentation. For the local oscillator feeding into the product detector, what frequency do you use? What considerations go into that choice?
Well, my friend, in this case the balanced mixer I used operates at 455 KHz, so the RF source has to be 455 KHz. It is a fixed frequency source. The signal then goes into a 455 KHz IF which feeds another mixer. This is where the variable frequency local oscillator comes into play.
One the other side of the coin, the product detector. Again, this chip, when used as a product detector, is expecting 455 KHz. It uses a fixed frequency source and the I.F. coming from the I.F. chain at 455 KHz. Ahead of the I.F. chain is the mixer responsible for taking the R.F. and down shifting it to 455 KHz. The local oscillator feeding this mixer would have to be set to a frequency that is 455 KHz off of the receive frequency to do this. This mixer is followed by the I.F. chain which consists of amplifiers and filters so the anticipated artifacts of the mixer do not make it to the detector. Hope this helps
@@eie_for_you It does indeed help. Thank you. The only thing I'm curious about now is it sounds like the 455KHz must be some established standard. Otherwise it sounds like the source station could be modulated with 455 and if no standard then a receiving station could be using something else entirely. Or, am I missing something related to this xmt/rcv situation....? Thanks.
@@NickFrom1228 Yup, 455 KHz is a very standard I.F. frequency that has been in use for a very, very, VERY long time. It is not the only standard, however, but it is probably the oldest. It was chosen so as to avoid a bunch of artifacts associated with mixers that cause problems downstream. From the receive perspective, it really doesn't matter what the I.F. frequency of the transmit station was as long as we add in a carrier at our I.F. frequency at the receiving end.
@@eie_for_you Excellent. That clears it up nicely. Thank you, God bless and have a great weekend.
@@NickFrom1228 You have a great weekend, too! 🙂
Dear gentleman, I would be pleasured if you can answer to my follow question. If I have a theoretical periodic and perfect-shape sine wave, what I can see on the spectrum analyzer? I expect to find a single frequency, isn't it? No any harmonic. Thank you for spend time to answer me.
If you have a perfect sine wave and your mixer/modulator does not contain any non-linear characteristics, then you will see one pip at the modulation frequency on either side of the carrier frequency (DSB).
@@eie_for_you Thank you for your answer, gentleman. I meant a pure signal, not a modulating signal over a carrier. In my case, again, will I see only one vertical line on the spectrum analyzer, correspondig to that sisgnal? (I'm trying to find out a book, but all books (signal & systems) have an heavy mathematical base which I would like to overlook, looking for the practical conclusions. I would be grateful to you if you can suggest me this kind of document/book, a sort of "signal & system for dummies", that can explain the real examples of modulated signals emitted by a radio and how we can see these on a time domain and frequency domain. Thank you very much indeed again. 73 de IZ7VHF.
@@RobertoPietrafesa No modulation of any kind - a single pip on the screen which is the signal in question.
Here is an interesting read to parse out around the math:
drive.google.com/file/d/1AvVF_RyaYbevQHYDLhYaxsXs8IWPQy9o/view?usp=sharing
@@eie_for_you Thank you Mr Ralph for this suggestion! I will read it deeply and soon. Clark Gable is to american actors as Ralph Gable is to youtube trainers! 🤩
@@RobertoPietrafesa There is also these four videos that might be helpful:
ruclips.net/video/vlIINDI0joE/видео.html
and
ruclips.net/video/TaR8AYGjqv0/видео.html
and
ruclips.net/video/pM3WZqfC6Sc/видео.html
and, lastly ...
ruclips.net/video/gPUqWXEWI94/видео.html
Hello, I study electronics and radio communication for my own so I have nobody to ask my question and in books it is explained similar to your video but I still don't get it. Let's say I want to create AM signal with carrier wave 100 000 Hz and I want also to transmitt my stable (and very boring) audio signal 1000 Hz and what I don't get from where do I have other frequencies than my carrier 100kHz and signal 1KHz ??? I use my oscilloscope and I see this beautiful shape of AM modulation , I see my carrier and waves higher and lower in voltages which creates all of this and my signal formed by this carrier 1 kHz but where do those 3 kHz etc. come from? Where can I find sidebands looking at my oscilloscope (I know it is a little bit childish question but I don't know how to explain it).
The additional sideband signals that we see are from harmonic distortion in the modulated signal. If we had a pure, perfect 1 KHz tone (without any harmonic distortion in it) and a perfect modulator, then we would only see the single 1 KHz sideband pip. But, alas, nothing is perfect. So we get this additional "stuff." The only way to see it is using a frequency domain device like a spectrum analyzer or an oscilloscope with FFT capability.
Hope this helps dispel the fog a bit.
@@eie_for_you Thank you for the answer! I see now. So If I had a lot of distortion I would have a lot of other frequencies on spectrum analyser? Or it is the case also when I can hear my 27 MHz singal on my radio tuned to 2,7 MHz ? So it is like a bad copy of my oryginal singal in different frequencies? I am trying to understand this. I always discover something strange which doesn't follow the explanation from the book.. I know that the examplaes are ideal examples but still some authors can't explain simple things or maybe they can't ...
@@grzesiek1x Yes. The more distortion, the more frequencies you would see on the spectrum analyzer.
You could have some Excel fun with this...
An AM signal has the equation
v(t) = (1+sin(2*pi*fmod*t))*cos(2*pi*fcarrier*t)
where fmodulation is the frequency of the modulation, fcarrier is the frequency of the carrier, t is time in seconds. This assumes a sine wave modulating the carrier.
Excel will do an FFT. You use this equation to generate the time domain signal, use Excel to do the FFT to get the frequency domain stuff.
@@eie_for_you Thanks again, I will try it :)
May I try to add some basic explanation for you ? It is some understanding that got to me recently, so I am glad to show it.
Have you ever tuned an instrument with a tuning fork ? Lets say a guitar, and the snare to be tuned is slightly off. When you strike the snare and fork at the same time, you will hear 4 things: the frequency of the fork, the frequency of the snare, AND the difference between these two, AND the addition of the two, often less noticeable. When the fork is 880 Hz, and the snare is tuned as 882 Hz, you will also hear the 2 Hz difference as a wining extra sound. And there's also the total (addition) of the two basic tones, 880+882=1762 Hz, less noticeable than the 2 Hz.
In this story, the 2 Hz and the 1762 are side bands, extra wave energy left and right of the two main frequencies of 880 and 882 Hz.
By the same principle two extra energy bands form when you take a carrier, and ADD a modulation on it. The guitar example were low frequencies, and the difference was small (2 Hz), while the addition was large (1758 Hz) compared with the ground frequency of 880 Hz. But if you use an example of 10 MHz with a modulation of 1KHz, the subtraction is 9.999.000 Hz and the addition is 10.001.000 Hz. Two extra frequencies are formed, the side bands, with the carrier in the middle.
When you would not use 1000 Hz modulation, but spoken word, a whole spectrum is formed as side bands close to the carrier.
I think it is not possible to see these bands on a normal scope, because they linger to close to the carrier frequency. That is why they use a spectrum analyser, so you can see how the different frequency energies are distributed around the main frequency.
WHY DIDN'T YOU SHOW SSB IN THE TIME DOMAIN???????!!!!!!!!!!!!!!!
Actually ... I did show an SSB signal in the time domain starting at 10:19.
@@eie_for_you that was DSB
@@MrStickyPete And double sideband and single sideband looks the same in the time domain.
@@eie_for_you the difference frequency must be visible somewhere in the time domain
@@MrStickyPete Sorry to break the news to you, but ... nope. I'm looking at the time domain trace of a single tone modulated SSB signal and it looks no different than the DSB. I check my ARRL radio amateurs handbook, same story. 🙂