I love this stuff. Some things were never taught in academia. Going to the other step wasn't clear for engineers. I took the electives that covered microwave and antenna design. Basic research I've done wasn't clear how to push for higher level stuff. But this video is everything I needed. It confirmed and abolished some of my doubts.
Awesome. I inherited teaching this course from others in the department back in the 1990s. The combined lecture/lab/build paradigm is definitely the way to go (at least at the upper level classes). Have also created a lecture/lab course like it for antennas and microwaves and I'm working on an "Antenna Briefs" series to support that too (at least the antennas part of it). Thanks again for the feedback on how the videos come across. Very nice to hear 🙂
Recently a ham friend of mine who's also interested in this subject commented that every once in a while, you come across some nugget that's like a missing piece of a puzzle. That's so true, but anybody who has ever done a jigsaw puzzle knows that the first thing you do is find all the edge pieces and put them together. It's the easiest thing to do and it defines the bounds. That's what this series is doing for me. Oh, I'll drill down at but for now, fleshing out the boundaries is where I'm at. And on a side note, I've got almost no formal education in these matters but I'm having fun rectifying that with this wonderful resource. I've built a few common emitter Colpitts's on a breadboard here and yeah, they worked up to about 1.5 MHz, but you're helping me in understanding the why(s). Thanks again.
Awesome. I'm glad to hear the series does that. Thanks for the excellent analogy with jigsaw puzzles. I hadn't thought of it that way ! I don't know if you've seen it yet, but there's a companion website for this channel. It has all the slides used in the videos as well as some info on "RF circuit prototyping boards", and raw notes from the course from which this series was derived. If you are interested, see: ecefiles.org/ Thanks again for the encouraging words! 73
@@MegawattKS Yes, I've seen it and downloaded some of it into a binder. Just had open heart surgery this week so I'm running a little behind lol but anyway God bless you sir
Thanks for this great series. Loving it. Had to watch a few portions multiple times(i an probably getting old) to have all of it drilled in. Thanks to internet, leveled the field for individuals like me from 3rd world with such high quality educational content.
Quick question. You want a low phase noise oscilator, because you dont want to increase the constallations when working with frequency modulation correct?
There are a number of performance issues for both transmitters and receivers relative to phase noise. For high-dimension digital modulations (e.g. 256 QAM like in cable systems), it impacts receiver sensitivity and error rate floor as well as spread the constellation in transmit mode. More generally it can cause "blocking" problems in receivers from nearby strong interferers or cause spectral pollution from transmitters. But to be honest, except for things like high-dimension QAM, it's impacts are often over-rated and its just one of those things that products compete against each other with (like noise figure in a terrestrial receiver which is arguably not very important given the elevated noise floor from terrestrial interference). Sorry - that's a long answer...
This video helped me a lot. Can you explain why LC oscillators usually have significantly larger feedback capacitors that crystal oscillators operating at the same frequency? Also since there is no limit on feedback build up it seems that the amp will be driven into Class C. Does this give a distorted output or does the LC tank circuit help produce a sinewave?
Interesting question. There are a couple of reasons I can think of (but I confess to not having really considered this before). For example, crystal oscillators can have good stability and good phase noise (because their Q is very high) even at low power levels in the amp the oscillator is based on. Lower C values mean higher impedance, which means generally lower current in active devices. Hence low power operation. It's also possible that the crystal frequency is most "accurate" (relative to what its marked as) at a particular C value, whereas LC oscillators are looking for the highest Q value and C will be varied anyway. On the question of the oscillator amp being driven into class C. Yes - you are absolutely correct. The active device (e.g. transistor) is definitely switching on and off over a cycle and the LC tank circuit takes the pulsing current and smooths it into a nice sinewave :-) How deep it goes into class-C mode depends on the starting loop gain - which is usually at least 2 to guarantee the oscillation starts. It turns out that the signal level with feedback is limited. Once the amplitude builds up and the current waveform becomes pulse-like, the amplitude in the fundamental frequency falls and the loop gain settles to one.
@@MegawattKS Thanks for your comments. It's great to find material on oscillators. Books that I have read in the past have always avoided oscillators and mixers. Your videos are invaluable. In the future maybe you could do something on PLLs? I'm particularly interested in the filter design i.e the choice of pole/zero frequencies in a simple RC filter. I read application notes in the past but they only deal with PLL filters for a capture/settling time perspective. I'd like a practical design methodology that looks at keeping the phase noise low in ham radio applications. An approach based on the well established CD4046 would be ideal. Mike (in Germany)
@@mikewhelan5992 Here is another good book and it seems to cover the things you're interested in. The Design of CMOS Radio-Frequency Integrated Circuits, Second Edition 2nd Edition by Thomas H. Lee www.amazon.com/Design-Radio-Frequency-Integrated-Circuits-Second/dp/0521835399 . The Amazon page also has a "Look Inside" where you can see the table of contents and the very extensive index. The sample text and title are a little misleading. It says "CMOS" in the title, but its really just about radio circuits. And the sample text doesn't go far enough into the book to show how it covers circuit design. It is only the radio pre-history part. The actual technical material is pretty detailed later in the book and covers up through oscillators, plls, phase noise, etc, It's written at a university level, but I like how Lee has a history similar to my own in ham radio, and comes at the subject from an understanding that goes well beyond the math alone. 73 Bill
Can you give a little more explanation about the synthesizer circuit at time 30:38? It looks like you are using an ethernet jack to the VCO? And is the VCO one that your students designed, or is it off the shelf? Thank you!
The synth board is one I provided to the students to try with their radios if they wanted. It was designed to lock their VCO that they built. Normally that VCO is tuned with a potentiometer to provide voltage tuning. That's what we did in 99% of the final exam check-offs. But if the pot was disconnected, the synth board could supply that voltage and control it to tune to precise frequencies. The synth chip used was originally an LMX2306, but that's obsolete now. A possible choice now might be an Analog Devices ADF4002. I just used a common TCXO as the crystal reference. I think it was a CSX532T19.200M3-UT10. I also had an old PIC microprocessor on the board - but later I used an Arduino when we used this in another class. The jack is nothing special. It as just an RJ11. But it could be anything since the synth signals are low frequency. I think we normally used a 100 kHz divided-reference frequency forcing a 10 kHz loop bandwidth for stability...
@@MegawattKS Thanks for those details. I was just trying to follow along on my next steps. I have the pre-select filter built on a board. I've designed the amplifier in LT spice and am working on construction. So, I was trying to watch the next videos and plan what I would need to do.
THANK YOU FOR THIS EXCELLENTE REVIEW! Q1: is it possible to use the TinySA to generate a sweep wave in order to tune a typical FM radio from 70's? Q2: is it possible to add a 10.7Mhz marker to tune the S curve? Q3: how the stereo could be tuned? I have no much resources and i use a Chinese FM STEREO transmitter module with a 400Khz tone in both channels...
Thanks. I think the answer to Q1 might be yes. However, it depends on what you're trying to do and what the FM radio requires (and of course getting to the appropriate circuits). The TinySA has a maximum amplitude of about - 7 dBm when it's in output mode. Mine (and maybe all of them), can generate either fixed-frequency CW or swept signals. The NanoVNA (at least the one I have) can also generate CW outputs, and they are stronger: about +2 dBm below 300 MHz. Neither unit has any ability to add a Marker to the sweep in the traditional way (briefly increasing amplitude at specific frequency). But they're synthesized, so you can always set them to whatever frequency you want to investigate closely and do that manually, perhaps. Sadly, nothing is going to help with stereo tests. That requires a 38 kHz DSB modulation in the audio plus a 19 kHz pilot (also in the audio). The TinySA can create wideband FM (its less than +/ - 75 kHz deviation, but still wide in the technical sense) with audio modulation. But there is no audio input and the internal audio is not pure sinewave and only works up to something like 5 kHz. Hope that helps.
Great video! I am curious about the freq synth PCB board. Looks like it is a DIY PCB? And the traces are quite thin? So the questions are: 1) Is there a ground plane underneath? Is it just a FR-4 double layer PCB? 2) If there is a ground plane underneath, that will make PCB traces microstrip lines. I guess there are not of 50 ohm impedance since they are quite thin(
Good observations and questions. Yes - its a homebrew board created for the class use. There is a ground plane on the bottom and yes - it's just 2 layers. While the lines are technically microstrip due to the underlying ground plane, the frequency is so low that it's functionally just a PCB with the ground plane being used to limit parasitics and EMI issues. The wavelength at 100 MHz is 3 meters in free-space and about 1.5 to 2m on the PCB (depending on trace width to thickness), so traces are generally 1/100 wavelength or less on the board and the controlled impedance aspect of microstrip isn't needed.
Nice and very illustrative video, doubt at minute 24:32, when you use varactor, the total capacitance is: C1 + CB -- CA + CC -- CV? what is the recommended Cc value? Regards.
Yes - that's the basic value of the total C resonating with L1. However, that assumes the output coupling capacitor ( shown but not labeled) is small and/or it is driving into a very high Z load. Otherwise, that capacitor and the load will have an effect on the frequency (or even stop it from oscillating). Assuming that output coupling C is small relative to Ctotal, then the formula you gave should get you close. There are 2nd order effects also from Cbe and Ccb in the transistor - but they're usually negligible if we design as described in the video and the transistor used has an "f_T" value (max operating frequency) sufficiently high, which is the case for something like the class project's MMBR5179 transistor used in an FM radio design.
A better answer is probably to just make Cc small compared with Ctotal. Just keep in mind that the smaller you make it, the smaller the output signal level will be...
Can i enroll for the university course to do by correspondence? Im just interested in learning to build a receiver, not doing it for the qualifications, is the course available under these circumstances?
Sorry for the late reply. Unfortunately no. The course involved a lot of lab work and was never offered in that format. Now that the NanoVNA and TinySA became available, that could possibly change in the future, but I don't think the school has any current plans along those lines for that course. Thanks for the interest though. I'll pass it on to the current faculty. Again - sorry for the delayed reply.
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Your channel is fantastic! Thank you so much for sharing this knowledge that is rarely seen even in books.
You're very welcome. Thanks for the complement 🙂
Very well done. You are very good at condensing a large amount of material into a short time. No need to
Thank you!
I love this stuff. Some things were never taught in academia. Going to the other step wasn't clear for engineers. I took the electives that covered microwave and antenna design. Basic research I've done wasn't clear how to push for higher level stuff. But this video is everything I needed. It confirmed and abolished some of my doubts.
Awesome. I inherited teaching this course from others in the department back in the 1990s. The combined lecture/lab/build paradigm is definitely the way to go (at least at the upper level classes). Have also created a lecture/lab course like it for antennas and microwaves and I'm working on an "Antenna Briefs" series to support that too (at least the antennas part of it). Thanks again for the feedback on how the videos come across. Very nice to hear 🙂
Recently a ham friend of mine who's also interested in this subject commented that every once in a while, you come across some nugget that's like a missing piece of a puzzle.
That's so true, but anybody who has ever done a jigsaw puzzle knows that the first thing you do is find all the edge pieces and put them together. It's the easiest thing to do and it defines the bounds.
That's what this series is doing for me. Oh, I'll drill down at but for now, fleshing out the boundaries is where I'm at.
And on a side note, I've got almost no formal education in these matters but I'm having fun rectifying that with this wonderful resource.
I've built a few common emitter Colpitts's on a breadboard here and yeah, they worked up to about 1.5 MHz, but you're helping me in understanding the why(s).
Thanks again.
Awesome. I'm glad to hear the series does that. Thanks for the excellent analogy with jigsaw puzzles. I hadn't thought of it that way ! I don't know if you've seen it yet, but there's a companion website for this channel. It has all the slides used in the videos as well as some info on "RF circuit prototyping boards", and raw notes from the course from which this series was derived. If you are interested, see: ecefiles.org/ Thanks again for the encouraging words! 73
@@MegawattKS Yes, I've seen it and downloaded some of it into a binder. Just had open heart surgery this week so I'm running a little behind lol but anyway God bless you sir
@@Mark_KE8YCV Wow. I hope you're feeling better and get well soon, and have a happy holiday / Merry Christmas!
Thanks for this great series. Loving it. Had to watch a few portions multiple times(i an probably getting old) to have all of it drilled in.
Thanks to internet, leveled the field for individuals like me from 3rd world with such high quality educational content.
Awesome, thanks for the feedback. Watching a few times is definitely needed for some of this. Glad it is helpful !
This video answered several questions all at once for me. Thank you
Great to hear! Thanks :-)
Thank you for this series!
You're welcome. Thanks for the comment !
i am so loving these video..
Glad you like them!
Great video !
Thanks!
Great video serie. I'm looking forward to the next episode.
LB8X
Thanks ! Slides for next one are done. Just refining them now...
Thank you..
nice video learned a lot
Awesome. Glad it was helpful!
Very Good！
Thank you
You're welcome. Its nice to hear that it is helpful !
Thanks!!!
Dear Sir; the lectures are great source for us, you are requested to share the slides in pdf format. thanks a lot Sir
Thanks for the comment. The slides are available at ecefiles.org/ Hope they're helpful.
Quick question. You want a low phase noise oscilator, because you dont want to increase the constallations when working with frequency modulation correct?
There are a number of performance issues for both transmitters and receivers relative to phase noise. For high-dimension digital modulations (e.g. 256 QAM like in cable systems), it impacts receiver sensitivity and error rate floor as well as spread the constellation in transmit mode. More generally it can cause "blocking" problems in receivers from nearby strong interferers or cause spectral pollution from transmitters. But to be honest, except for things like high-dimension QAM, it's impacts are often over-rated and its just one of those things that products compete against each other with (like noise figure in a terrestrial receiver which is arguably not very important given the elevated noise floor from terrestrial interference). Sorry - that's a long answer...
muy bueno..!!
Thanks! Glad you liked it.
This video helped me a lot. Can you explain why LC oscillators usually have significantly larger feedback capacitors that crystal oscillators operating at the same frequency?
Also since there is no limit on feedback build up it seems that the amp will be driven into Class C. Does this give a distorted output or does the LC tank circuit help produce a sinewave?
Interesting question. There are a couple of reasons I can think of (but I confess to not having really considered this before). For example, crystal oscillators can have good stability and good phase noise (because their Q is very high) even at low power levels in the amp the oscillator is based on. Lower C values mean higher impedance, which means generally lower current in active devices. Hence low power operation. It's also possible that the crystal frequency is most "accurate" (relative to what its marked as) at a particular C value, whereas LC oscillators are looking for the highest Q value and C will be varied anyway. On the question of the oscillator amp being driven into class C. Yes - you are absolutely correct. The active device (e.g. transistor) is definitely switching on and off over a cycle and the LC tank circuit takes the pulsing current and smooths it into a nice sinewave :-) How deep it goes into class-C mode depends on the starting loop gain - which is usually at least 2 to guarantee the oscillation starts. It turns out that the signal level with feedback is limited. Once the amplitude builds up and the current waveform becomes pulse-like, the amplitude in the fundamental frequency falls and the loop gain settles to one.
@@MegawattKS Thanks for your comments. It's great to find material on oscillators. Books that I have read in the past have always avoided oscillators and mixers. Your videos are invaluable. In the future maybe you could do something on PLLs? I'm particularly interested in the filter design i.e the choice of pole/zero frequencies in a simple RC filter. I read application notes in the past but they only deal with PLL filters for a capture/settling time perspective. I'd like a practical design methodology that looks at keeping the phase noise low in ham radio applications. An approach based on the well established CD4046 would be ideal.
Mike (in Germany)
@@mikewhelan5992 Here is another good book and it seems to cover the things you're interested in. The Design of CMOS Radio-Frequency Integrated Circuits, Second Edition 2nd Edition by Thomas H. Lee www.amazon.com/Design-Radio-Frequency-Integrated-Circuits-Second/dp/0521835399 . The Amazon page also has a "Look Inside" where you can see the table of contents and the very extensive index. The sample text and title are a little misleading. It says "CMOS" in the title, but its really just about radio circuits. And the sample text doesn't go far enough into the book to show how it covers circuit design. It is only the radio pre-history part. The actual technical material is pretty detailed later in the book and covers up through oscillators, plls, phase noise, etc, It's written at a university level, but I like how Lee has a history similar to my own in ham radio, and comes at the subject from an understanding that goes well beyond the math alone. 73 Bill
@@MegawattKS Thanks Bill, Looks like a very good book. It covers all of the topics that interest me. I must pick up a copy.
Mike
Can you give a little more explanation about the synthesizer circuit at time 30:38? It looks like you are using an ethernet jack to the VCO? And is the VCO one that your students designed, or is it off the shelf? Thank you!
The synth board is one I provided to the students to try with their radios if they wanted. It was designed to lock their VCO that they built. Normally that VCO is tuned with a potentiometer to provide voltage tuning. That's what we did in 99% of the final exam check-offs. But if the pot was disconnected, the synth board could supply that voltage and control it to tune to precise frequencies. The synth chip used was originally an LMX2306, but that's obsolete now. A possible choice now might be an Analog Devices ADF4002. I just used a common TCXO as the crystal reference. I think it was a CSX532T19.200M3-UT10. I also had an old PIC microprocessor on the board - but later I used an Arduino when we used this in another class. The jack is nothing special. It as just an RJ11. But it could be anything since the synth signals are low frequency. I think we normally used a 100 kHz divided-reference frequency forcing a 10 kHz loop bandwidth for stability...
@@MegawattKS Thanks for those details. I was just trying to follow along on my next steps. I have the pre-select filter built on a board. I've designed the amplifier in LT spice and am working on construction. So, I was trying to watch the next videos and plan what I would need to do.
THANK YOU FOR THIS EXCELLENTE REVIEW!
Q1: is it possible to use the TinySA to generate a sweep wave in order to tune a typical FM radio from 70's?
Q2: is it possible to add a 10.7Mhz marker to tune the S curve?
Q3: how the stereo could be tuned? I have no much resources and i use a Chinese FM STEREO transmitter module with a 400Khz tone in both channels...
Thanks. I think the answer to Q1 might be yes. However, it depends on what you're trying to do and what the FM radio requires (and of course getting to the appropriate circuits). The TinySA has a maximum amplitude of about - 7 dBm when it's in output mode. Mine (and maybe all of them), can generate either fixed-frequency CW or swept signals. The NanoVNA (at least the one I have) can also generate CW outputs, and they are stronger: about +2 dBm below 300 MHz. Neither unit has any ability to add a Marker to the sweep in the traditional way (briefly increasing amplitude at specific frequency). But they're synthesized, so you can always set them to whatever frequency you want to investigate closely and do that manually, perhaps. Sadly, nothing is going to help with stereo tests. That requires a 38 kHz DSB modulation in the audio plus a 19 kHz pilot (also in the audio). The TinySA can create wideband FM (its less than +/ - 75 kHz deviation, but still wide in the technical sense) with audio modulation. But there is no audio input and the internal audio is not pure sinewave and only works up to something like 5 kHz. Hope that helps.
Great video! I am curious about the freq synth PCB board. Looks like it is a DIY PCB? And the traces are quite thin? So the questions are: 1) Is there a ground plane underneath? Is it just a FR-4 double layer PCB? 2) If there is a ground plane underneath, that will make PCB traces microstrip lines. I guess there are not of 50 ohm impedance since they are quite thin(
Good observations and questions. Yes - its a homebrew board created for the class use. There is a ground plane on the bottom and yes - it's just 2 layers. While the lines are technically microstrip due to the underlying ground plane, the frequency is so low that it's functionally just a PCB with the ground plane being used to limit parasitics and EMI issues. The wavelength at 100 MHz is 3 meters in free-space and about 1.5 to 2m on the PCB (depending on trace width to thickness), so traces are generally 1/100 wavelength or less on the board and the controlled impedance aspect of microstrip isn't needed.
Nice and very illustrative video, doubt at minute 24:32, when you use varactor, the total capacitance is: C1 + CB -- CA + CC -- CV? what is the recommended Cc value? Regards.
Yes - that's the basic value of the total C resonating with L1. However, that assumes the output coupling capacitor ( shown but not labeled) is small and/or it is driving into a very high Z load. Otherwise, that capacitor and the load will have an effect on the frequency (or even stop it from oscillating). Assuming that output coupling C is small relative to Ctotal, then the formula you gave should get you close. There are 2nd order effects also from Cbe and Ccb in the transistor - but they're usually negligible if we design as described in the video and the transistor used has an "f_T" value (max operating frequency) sufficiently high, which is the case for something like the class project's MMBR5179 transistor used in an FM radio design.
A better answer is probably to just make Cc small compared with Ctotal. Just keep in mind that the smaller you make it, the smaller the output signal level will be...
Can i enroll for the university course to do by correspondence? Im just interested in learning to build a receiver, not doing it for the qualifications, is the course available under these circumstances?
Sorry for the late reply. Unfortunately no. The course involved a lot of lab work and was never offered in that format. Now that the NanoVNA and TinySA became available, that could possibly change in the future, but I don't think the school has any current plans along those lines for that course. Thanks for the interest though. I'll pass it on to the current faculty. Again - sorry for the delayed reply.