#167

[@SamGallagher]

W2AEW, aka Alan, you're the KING of RF electronics videos. You hit the stuff I never totally understood, and in the best way. Rock on man

[@pdxfunk]

Fantastic video, thank you! Literally almost all the information on the internet is calling a 4 quadrant multiplier a ring modulator (It's not!!). This is the only video I've seen that gets it right.

[@arthursgarage6550]

Man, can I just say you are one hell of a good explainer of RF stuff

[@whawaii]

Thank you for this awesome presentation. As I was following the "Scope Overview" section where you list the 2 frequencies (7 MHz & 10 MHz) being combined, in my head I'm already calculating the resultant frequencies as 3 MHz & 17 MHz. You really threw me for loop at 2:08. I did a "What?!?" double-take & went back to hear that again when you stated that the upper frequency would be "13MHz". I started doubting my own RF & LO knowledge. Thankfully, the rest of the time you referred to the upper one as 17MHz. [You may wish to consider posting a notice of this misstatement.] Thank you.

[@hofjen66]

Your tutorials are the best I've ever seen on KZbin! 73 de DL1WW!

[@volvoC70II]

You did a great work, making sketches and explaining how the mixer works. In these 10min I have learned more, then from reading books for 3 hours. Thanks!

[@AppliedScience]

Very helpful and well explained, Alan. Thanks!

[@ernestb.2377]

Thanks for the explanations! There are so much specific details in RF electronics..

[@phoenixcrp]

The regular electronics hobbyist could not justify the expense of owning such a nice mdo piece of gear (around $14K tag price) I would like to thank you, Alan, for your generosity on producing videos like this one. The 50K frames in this video are priceless for many of your followers.

[@w2aew]

+Frank Acosta I do realize that I often use equipment that is outside the reach of the hobbyist. I am very lucky to be working for Tektronix and have access to this fantastic equipment. I hope that the use of this equipment serves to help viewers understand the topics and concepts being presented.

[@StreuB1]

+w2aew It does....I am a design engineer with a big mechanical background and a "working" background on the electrical side of things. These videos have really expanded my scope of understanding. Especially in the industry I work in. It opens my eyes to a lot of the things my companies technology does.....metal detection.

[@God-yb2cg]

I was actually thinking: "that scope would be a waste in my possession because I wouldn't know how to use half it's features"

[@Afrotechmods]

Another amazing video. Thank you Alan. If you are open to requests, I would love to see videos about mixers that use as few magnetics as possible with the goal of reducing PCB size and cost.

[@absurdengineering]

A trifilar transformer like this for say 2-5GHz is the size of a 1210 capacitor if you wind it yourself. It’s even smaller - a small grain of rice - if you buy it and it costs pennies. Kinda hard to beat with discrete parts. The only way to beat it is with transistors on a chip: those are usually “free” compared to anything discrete. So if you really want low cost, use a dedicated mixer IC, or make an ASIC for your application that will replace other discretes with free transistors :) When pricing discrete parts, the cost is in raw materials and processing of each unit: a discrete run-of-the-mill transistor costs about as much as a discrete inductor or transistor of a similar size and volume. When costs matter that much, you’re talking hundreds of thousands or millions of units. At such scales, small magnetics cost about as much as small anything else, to a first order. Even the costs of inserting the component start to matter at such scales. For anything made at hobbyist scale, the cost of labor wipes everything else. PCB and other stuff is essentially free, and it costs more to ponder about it than to just put it on the board and move on if it does the job to spec you need :k)

[@Whiskers1949]

I actually followed this all the way through.....a testament to your presentation. Thanks!

[@habiks]

Did they name a school after you yet?

[@w2aew]

No, not yet.

[@yytvo212]

The explanation on the diode circuit diagram is amazing and in-depth. Classroom courses pale in comparison.

[@outsideaglass]

Your videos have definitely saved me this term. With COVID19 shutting down the labs and everything's moved online, it's been really hard for me to learn just from my professor's lectures and no lab work. I was really struggling til I found your videos. Thanks so much!

[@w2aew]

Very happy to hear that!

[@stefanopassiglia]

Super. I got back to working on electronics after looking at one of your "back to basics" video, and I am still an audio frequency guy but I love learning about RF which is a domain I touched really very lightly during my studies. Thanks for these fantastic videos.

[@DantalionNl]

I love how detailed and in depth your rf videos are, your'e the only one who makes decent videos about this its awesome! keep it up.

[@retro.jonnes]

This is the best explanation about mixers I found over the YT! Thanks!!!

[@commandercortez]

I feel like it's worth mentioning that the non-linearity of the diodes is what makes the "cos(a+b) + cos(a-b)" (addition and subtraction of the input frequencies) components appear in the output signal. Otherwise, what we've created is just the sum of two signals sin(a) and sin(b), which can be achieved without the use of diodes or switching at all.

[@ozzyfromspace]

This is amazing! Who on Earth could have possibly disliked this video?

[@kolinevans9127]

The ‘never Tesla’ crowd ?

[@thisnicklldo]

Terrific video. It must take you a long time to get all these diagrams and oscilloscope setups working, but they really make things clear. Thanks.

[@w2aew]

Sometimes the preparation work for producing a video like this can be several hours, or even a few days of spare-time tinkering.

[@fjs1111]

wow Alan, that was awesome. I knew how mixing worked, but to see the ways you did this it really made me think.. Also -- that was really cool to see a custom math expression on a scope, I've never seen custom expressions before, only built-in

[@devjock]

I'm subscribed to the synth-diy mailinglist and there's so much material that's common between these two areas. Besides the diode nonlinearity, which in audio-synth territory gets kinda fixed by an ideal diode circuit (fancy balanced opamps), it's basically a ring modulator! Crystal clear explanation as always, much appreciated for uploading!

[@outsideaglass]

These videos are super helpful with the COVID19 quarantine preventing us from going into the lab (and with professors who aren't capable of making videos) - thanks a lot! You're a life saver!

[@UberAlphaSirus]

Thanks to you w2aew, RF is becoming less voodoo magic to me. Thanks :D

[@MoTown44240]

Jim, AC8NT my Extra Class instructor showed this and three more of your videos tonight. I am one of those is having/ has been having a difficult time understanding electronic theory. I am struggling. Now that the former Advanced and former Extra class material is combined I will be attempting to pass Extra in 5 weeks. This is my 2nd time in Jim's class, last time was 18 months ago, and I am still having difficulty grasping the ET concept. Thankful for guys like you and Jim though. Terry KB8AMZ

[@ronjones4069]

By far the best, clearest explanation of how the DBM works. I kinda' understood them, but now I feel as I DO understand them. THANK YOU!! You are the man!!!Ron K7RJ

[@w2aew]

Thank you for the nice comments! I hope you find some of my other videos just as helpful. Be sure to check out the video index .pdf file that is linked on the main channel page (lower right corner of the banner graphic).

[@MrCarlsonsLab]

Hi Alan! I have recently found your videos through making my own. I Just started making videos, and guys like you are a great inspiration to keep going. We have a lot in common I see. I have a scope collecting problem "ha ha" ....... Well, test gear collecting in general.... And so on. Great Videos! And keep it up. My subscription list is still small, but your now in it!

[@w2aew]

Thanks! I've subscribed to your channel too.

[@m8uwut]

Lots of info, learned something new today. I'm sure it will be helpful in the future. You're doing Gods work.

[@ToddFun]

***** At 5:15 the circuit on the right doesn't have an LO input but does have an IF input and an IF output. This is a mistake? or is there something I don't quite understand?

[@w2aew]

Good catch! Of course, the port on the left of the right-hand circuit should also say LO.

[@copernicus633]

Question about theory: The diode ring mixer shown here seems very different from the Gilbert Cell mixer described elsewhere. The diode ring seems to “chop” one frequency with another frequency. That doesn’t seem like “multiplication”, but more of a harmonic creation mechanism. The undesired harmonics are eliminated with filtering, but with losses from the energy spent in suppressed harmonics. The Gilbert Cell seems like a true multiplication, where the product of 2 sinusoids is produced accurately, without creating a lot of extraneous harmonics. It is therefore less noisy. Is this a roughly true comparison?

[@w2aew]

Basically yes. The diode ring can be though of as a multiplication of one signal by an alternating +1 and 0, or +1 and -1, as opposed to a continuous multiplication. Even the Gilbert Cell can (and is often) be driven into limiting, thus giving a similar result to the way the diode ring mixer works.

[@allanseward7293]

It was great to visualize the results from multiplying the cosine waves at different frequencies. Thx

[@berni8k]

Thanks for the nice and simple explanation, i don't do RF stuff but i always wondered what these mixers are that i see everywhere.

[@wizardofboz76]

Very interesting.. its like you have a rectifier switched by the RF?

[@striker851]

Thank you for such a well thought through explanation. I'm still trying to wrap my head around AC waveforms and the math, but you really helped to visualize it.

[@gregorymccoy6797]

Thanks so much. I came here from your other mixer video. I've got a good handle on this now, at least for this type of mixer. I'm more of a digital domain, embedded guy but am getting the urge to try some RF projects.

[@zerovolt24]

Hi Alan, would 32 AWG also be ok? T37 is really small. Maybe 30 AWG is good for bigger toroid diameters too, so I can only buy one coil to suit all.

[@w2aew]

Sure, that would work

[@emylrmm]

this explanation is very nicely done

[@garygrove2884]

Very interesting video Alan !! I noticed that my IFR-1000S has similar circuits that seem to mimic your Diode Ring Mixer video !! 73's Gary Grove

[@stephenmoore2754]

Thanks very much for an informative video. Sometimes it takes one key piece of information to turn the light on in the ole noggin and you did it. I have been wondering for years just WHERE the information in an AM signal (sidebands) was located with respect to the overall signal. Watching it on a spectrum analyzer is one thing, but to see in on a scope trace is another. You answered a question that has been bothering me for years. I know that you can see the relation in the math, and that "stuff" may be found in other quadrants of the graphs, but your explanation finally showed me HOW it is related in the time domain. Great stuff. Now if I can translate this to a better understanding of SSB. . . . .

[@AntiProtonBoy]

One of the things that is a real grey area for me is winding coils and transformers for a circuit like this. Is there are good introductory material on choosing the right ferrite material, geometry and so forth? Perhaps you could discuss this topic in a new video, if appropriate?

[@TrystansWorkbench]

Here is one of Alan's videos on winding the coils for this: kzbin.info/www/bejne/l2m5moqJa5abqbc

[@TheBrandel111]

Finally, I understood this circuit! Thanks W2AEW!

[@holden0]

At 5:15, shouldn't the IF on the right-side diagram have an LO at the upper left node (like in the left-side diagram)? Because you already have an IF output at the RL?

[@w2aew]

Yes, there is an error in the video. The downloadable notes pages have been corrected.

[@markbell9742]

The ‘Math Expression’ in Tek MDO3104 is very neat; a scope married to an Excel spreadsheet (or to the more highfalutin: MATLAB or Mathematica). Cheers, Mark

[@omsingharjit]

please explain and make little circuit of how Tuning Meter Led indicator circuit works in old Radio ?

[@JimGriffOne]

I tried building one of these to make a 38kHz DSB-SC subcarrier for my FM radio transmitter. It worked, but my whole project failed when it came to trying to make a nice 19kHz pilot tone (sinewave) while also having a perfectly in-phase 38kHz sinewave to modulate the L-R audio. It gets so complicated! Wish I'd chosen electronics when I was college age.

[@rustukaya9342]

Thank you sir, couldnt be explained better.

[@tulsEE87]

Thanks for clearing concepts. Can you please say is any low frequency (kHz) QPSK modulator available or not?

[@jeffscaparra6985]

So would using a square wave for the LO clean up the signal because the diode mixer would transition on and off faster? would some weird combination of a square and sine be better? Is this accounted for in actual circuits or is a different type of mixer preferred?

[@caulktel]

Jeff Scaparra There is a lot of discussion over on the Bitx20 .io groups about this. Personally, I would rather use a sine wave rather than a square wave full of harmonics. Joel KB6QVI

[@jeffscaparra6985]

Cool I will check that out

[@RechargeableLithium]

Joel - we want to use a square wave because we want the sharp turn-on and turn-off of the diodes. Matching the four diodes, feeding enough power in from the LO, and having a 1:1 SWR at all three ports will keep the signal clean. For more, Pete Juliano has a three-part KZbin series on the topic, and details can be found in "Solid State Design for the Radio Amateur" as well as the 'QRP Homebuilder" archive. nt7s.com/files/QRPHomebuilder.pdf kzbin.info/www/bejne/oavGp4GwpbKpabc 73

[@johnc8910]

Disagree. You do NOT want extraneous harmonics generated in your mixer. Extraneous harmonics give extraneous images which can complicate selecting just the desired sum or difference frequency. Diode matching is not a problem with modern components. You can buy a quad ring part with 4 matched diodes for less than 4 individual diodes. Optimum LO injection is 7 dBm.

[@neodiy]

If we add two more diodes into the ring and one more center tap inductor ....what will happen? will it also mixed signal altogether?

[@w2aew]

Without a schematic, I don't know what you'll get

[@kedmark]

Exactly what I was looking for, tyvm for posting.

[@joaopaulocoelho5401]

Another perfect video. It would be nice to talk a little about the transformer. How the number of turns was found? Any math involved or just trial and error? Thank you!

[@schwinn434]

At the 6:00min mark, or so, I don't understand the comment (to paraphrase): the secondary of the transformer is shorted, and, therefore, the node "between" the left two diodes is at ground, with respect to the radio frequencies. Do radio frequencies currents flow from the ground of the center-tapped secondary, of the left-most transformer, through the top-left most diode and then to the negative bottom node of the transformer on the leftmost portion of the circuit, with the previously mentioned diode being forward biased?

[@w2aew]

The small signal resistance of the forward biased diodes is very low, so they "look like" very small value resistors to the right-most transformer windings. The effect is that each end of the center-tapped winding on the right-most transformer is alternatively grounded with each half-cycle of the LO signal.

[@schwinn434]

@@w2aew I did watch your videos on using Diodes as switches (which I thought were fascinating, BTW: #82 ' "How to use a diode as a Switch", #118 "Basics of pin diodes and their use in RF switching" , #200 "T/R switch with pin diodes and lumped element quarter-wave transmission line"), but I thought DC biasing currents were needed to forward bias the diode, and not AC currents, in order for a diode to work as a switch - hope this makes sense.

[@w2aew]

@@schwinn434 The diode is used as a on/off switch by forward and reverse bias - it doesn't have to be DC. In this case, the positive half-cycle of the LO turns on one pair of series diodes, and the negative half-cycle of the LO turns on the other pair of series diodes.

[@schwinn434]

@@w2aew Sorry to keep on about this matter, but I was wondering if you could build this mixer and actually see the radio frequency, from the rightmost transformer, superimposed on top of the forward biasing diodes in question- or would the vertical voltage sensitivity of the standard oscilloscope be too small?

[@w2aew]

@@schwinn434 yes, you can see it with the scope (unless the RF signal level is very low)

[@bain5872]

Exceptional! Truly enjoyed it.

[@maro8D]

Hello Alan, great video as usual! But I have some questions to it: 1. You have your LO amplitude set to 400 mV is it enough to switch on 2 diodes? When I see a diode I automatically think of 0.7 V voltage drop. I think it's hard wired in my brain after school :) 2. I understand that the RF signal amplitude must be below voltage that turns the diodes on is that right? So that only LO controls the diodes. Did I get it right? 3. Is the LO amplitude picked so low intentionally so that there is not clamping from top and bottom?

[@w2aew]

Hello Marek. I'm using 1N5711 low power schottky diodes in the ring. The Vf for these schottky diodes is about 1/2 of that a regular junction diode. The LO is used to modulate the diodes. The RF level is generally kept well below this to minimize distortion. Best (lowest) conversion loss occurs when the diodes are fully switched on/off, but the mixing happens even if this isn't the case. As long as the LO and RF are combined in a non-linear manner, the mixing happens - it's just that the conversion loss will be higher. When the LO power is high enough to fully switch the diodes, there is a fair amount of harmonic distortion visible on the LO drive waveform. For this video, I didn't want to get into that level of detail, so I kept the LO drive lower to keep the video length reasonable. Thanks for the good questions.

[@stevejin9459]

Marek The mixed two signals on diode should be less than 0.6v( for silicon diode) to have less current. That makes the load to both transformer light, hence less signal distortion to signal source. Also, less power consumption by the circuit. Diode has non liner v-I curve, in all range from 0.x volt to couple volt. That how the diode makes the added voltage of the two sources to multiplied current, measured by the resistor in serial . The diode ring also called ‘Gilbert cell’ question from stackoverflow, electronics.stackexchange.com/questions/307776/why-do-diode-rings-multiply

[@SopanKotbagi]

What kind of diodes can we use for making these double-balanced diode-ring mixers? And what determines the frequency window of operation of these mixers, if any? Great video as always. Thanks!

[@w2aew]

High speed schottky diodes are the most common. The design of the transformers (number of turns, core material, etc.) will largely determine the operating frequency range.

[@TechTins_Projects]

Thanks for this. Love it. I never really understood diode mixers. Now I do!

[@gregpeterson7946]

One aspect I have not seen addressed (yet) is drive level. The signal amplitude at the diodes I think should be at least 1.5 v, since 2 x silicon diode voltage drops of 0.7 v would be at least 1.4 volts to turn them on. But I do not know what the transformer ratio is, so I cannot guess at the LO amplitude. I also would like to play with IF filters, but do not know the proper drive level. My initial thought would be to drive a filter (mechanical, crystal, or piezo) with a sig gen at the filter's center frequency, slowly increasing the amplitude until I see some saturation evidenced by output ceasing to increase. At some point, I would expect damage from excessive drive, so I would like to stay below that. Radiofun232 comes close to addressing this with some of his lash-ups, but my questions remain unanswered.

[@w2aew]

I do address this topic in this video: kzbin.info/www/bejne/fafElYSmoL9ropI

[@guenaziz2]

Thank you so much for this video. I tried to find good explanation of how could diodes make the mixing, but never found any relevant one. Thank you Alan!

[@ericacopenhaver]

Thanks for this tutorial! Why, however, does the LO alone set the direction of the current in your analysis? Why doesn't the RF signal affect the current? Do we need to assume that the LO's amplitude is much greater than the RF?

[@w2aew]

Yes, that is typically the case. When you look up commercial mixer specs, you see Level-7 mixers, Level-10, Level-13, etc. This refers to the power of the LO signal (7dBm, 10dBm, etc.).

[@johnrinehart]

That was a really good explanation. Thank you very much for this. The only (small) modification I would have made to this video would be to change the math to have your logic driven by the transition level of the diodes (assume .6v for the 1N5711) only after you show the IF signal at the mixer output. This would help demonstrate that the zero portions are due to diode transitions. I saw that you used the LO to demonstrate this. But, it would have been good to see that mathematical waveform approach the measured wave. Also, it seems that the measured signal lags behind the math waveform (see 8:52). But, it's hard to tell without taking the difference of the mathematical waveform and the measured signal. Can you confirm that this is happening and can you explain why this might be happening? Thanks, again. Really, it was a great video. I could not have done better myself.

[@w2aew]

John Rinehart Thanks for the nice comments. I haven't taken that close a look at those small phase shifts, although it looks to me that the measured waveform is slightly leading the math waveform. I suspect that it is at least partially due to the difference in phase shift through the transformers (and I was measuring the signals on the primaries.

[@josepaul2000]

Thanks for the video! I am wondering, at 4:42 , could the 'LO' may well be a square wave? (since the mathematical expression simply detects the zero crossing) If so, the output doesn't seem to look so bad, why do we care so much about getting a low distortion sinusoidal oscillator? Or is that more relevant in circuits with 'better' mixers?

[@w2aew]

It does depend on the mixer design, but in this case, a squarewave LO would work

[@awesomeblossom6557]

Great informational video! Your videos help a great deal when I'm trying to work out something of my own. Quick question: @ 6:42 when you are explaining the negative state of the diode mixer ring, I'm assuming the input is still LO, but in the video and in your copy of the notes, it's written as IF.

[@w2aew]

Yes, this is a mistake in my notes. Thank you for paying attention!

[@w2aew]

I've edited the PDF to correct it and uploaded it.

[@awesomeblossom6557]

Ah wow! Thank you sir, appreciate it.

[@danielperez761]

Excellent explanation of the operation of a mixer. Regarding to it, I have a question to you. I need to compare two input standard signals of 10MHz. I could use a good interval counter to do it, but I need to have a better resolution. Then we decided to use a frequency mixer in order to obtain a frequency difference of some Hz ( 300-500Hz) at the output. My question is how to calculate the construction of the two baluns (how many turns and the diameter of the wires) so they can work on that frequency with the same circuit that you show in the video.

[@w2aew]

daniel perez General practice is to make the inductive reactance of the winding to be 4 or 5 (or more) times the impedance of the circuits driving it. For 50 ohm applications (typical), the windings should results in a reactance of 200-250 ohms or so. The number of turns can be determine by using one of many online calculators like the one shown here: toroids.info/

[@danielperez761]

***** many thanks for your quick response! It is very useful to us and we will build our mixer immediately in accordance with the data that you have provided us.:)

[@pneptun]

at 6:15 (the most replayed point of the video) why would the point between the diodes appear as ground? that would be true if the diodes behaved like a voltage divider, but they don't. they behave like a short. so it probably can't be the diodes (when conducting, they should behave as if they were not there, except for the threshold voltage drop. other than that they are basically just a shorting wire, right? and across a wire, even a shorting wire, the voltage should be basically the same everywhere, it doesn't behave like a voltage divider) so i was thinking - is it the resistance of the wire that makes up the actual coils of the centertapped transformer? so we could think of it as having two invisible, internal resistances equal in size, and THEY act like the voltage divider? cause if we replace the transformer with an ideal symmetric voltage source: -Vlo and +Vlo; and the diodes with ideal diodes with 0 resistivity after threshold, then i don't think this would work. so it must be the things _not shown_ in the diagram doing the work...

[@w2aew]

Remember that this diode string is being driven by the secondary of a transformer that has a grounded center-tap. The RF voltage is symmetrical (but inverted) at either end of the transformer secondary, thus the mid-point at the diode junction will appear basically at ground potential because the midpoint (center tap) is grounded.

[@pneptun]

@@w2aew thank you for the response! why would it be? it being center-tapped only means nothing from the point of view of the diodes. let's say the end voltages on the transformer are +2V and -2V. the diodes only see input voltages whose difference is 4V. they are not aware of any ground. as far as they're concerned it could be 0V and +4V. voltages are strictly relative, and they don't have any reference to the center tap. if you replace the diodes with a wire (because they are forward-biased) you wouldn't expect "the middle of the wire" to be at at 0V (or any midpoint voltage, between the voltages applied to the ends of the wire), would you? so why are you expecting the diodes to be? they're not a divider either. if you try it - take 2 diodes apply voltage to them and measure voltage between them you won't see them divide it. 🤔 so - i believe/know that the midpoints are at 0V, but the reasoning seems strange to me. (or maybe i'm misunderstanding it)

[@w2aew]

@@pneptun The fact that the diodes are driven from a winding which has a grounded center-tap *does* mean something. Using your example, the +2V and -2V at the ends of the winding *are* with respect to ground. Given a matched set of diodes, the voltage at the junction will be at 0V potential with respect to ground. The voltages at far ends will be the +2 and -2V when the diodes are reverse biased, and will be at clamped at +Vd and -Vd (with respect to ground) when forward biased, with forward current determined by the source impedance on the primary and the turns ratio.

[@pneptun]

@@w2aew i believe that. but _why_? before the first diode the voltage is +2V - coming right off one end of the transformer, after the first diode it should be 2-0.7=1.3V, not 0V. or is it that because the diodes are basically "shorting" the transformer they pull the voltage down? but that's basically what i said - the "pull down" is usually interpreted as realizing all of the voltage on the hidden internal impedancies. i think that's it - it's the internal impedancies. i'm convinced now.

[@robertfranks5376]

Hi Alan. I had a question about your directional coupler video. You used the outside conductor of a piece of coax as a Faraday shield by grounding one side. Why doesn't this allow signal current to flow in the shield, and wouldn't this cancel out the EM energy from the inner conductor so that the toroid current- sensing xfmr would sense zero current since the toroid surrounds both conductors. Thanks.

[@w2aew]

The faraday shield does not block the magnetic field (only the electric field), so there is still magnetic coupling to the toroid transformer.

[@robertfranks5376]

@@w2aew Hi Alan. Thank you so much for your response. I was thinking that the magnetic field from the electric current returning through the shield in the opposite direction to the current in the inner conductor would cancel out the magnetic field from the current flowing through the center conductor. Thanks again.

[@markussteinbacher8807]

very informative video. Thank you Alan. Did the amperage in this system rising when reducing the frequency ? aka mix 100khz with 1 vpp and 50 khz 1 vpp equals 150 khz and 50 khz with twice ampere ?

[@ebear1ca]

I have re designed the front end board in my old Yaesu FT-101 by Replacing the RF amplifier FET with a 3N211 or a 40673 which I have and using a MC1495 as a 1st recieve mixer as well as the 2nd recieve mixer to get rid of some of the birdies found in the rigs pass band. After what you tell me about dynamic range and higher intercept points I am now concidering using either a shottkey diode DBM or DDBM if I have enough LO drive. Ted VE6AMR

[@СтаніславЄрмоленко]

Thank you very much for detal video about diode ring mixer!

[@dustinl5372]

Where did you get your inductors from? Do you have a part number? If hand-made, what is the gauge of wire and numbers of turns?

[@w2aew]

I wound the transformers myself. 10 turns, tri-filar wound on a T37-6 core.

[@arimateiaalves3349]

Congratulations great video, wanted to know if when you were measuring the signals used some component that is not described in the list I could not reach the measured results

[@w2aew]

The parts I used are listed on the first page of the notes. www.qsl.net/w/w2aew//youtube/Diode_ring_mixer_operation.pdf

[@arimateiaalves3349]

thanks

[@Falican1]

Hey! do you have a video where you explain about the harmonic terminations to avoid reflections? thanks!

[@w2aew]

I'm sorry, I don't...

[@AKsizzle47]

If my understanding is accurate, mixing the two frequencies by multiplying them is essentially amplitude modulating them. However, in mind mind when I think AM, I envision a signal that is symmetrical about t = 0 axis. What are the differences in generating these types of AM signals and what kind of circuit modulates symmetrically?

[@w2aew]

+AKsizzle47 There are lots of ways to mix signals. Combining the signals through any non-linear process will create the mixing products. In this case, the multiplication is bipolar, that's why you don't see the symmetry you expected. In a balanced mixer like this, the original carrier is suppressed, and the sum and difference frequencies are most dominant.

[@christopherwells4768]

Even though only one half of the RF transformer is used at a time, do the coils used by the opposing polarity not resist the conducting of current in that direction, since they are all mechanically connected?

[@w2aew]

The "unused" half sees a high impedance, so no current flows.

[@danedewaard8215]

You explained very well how the LO changes the polarity of the IF output, but there is a more complicated interaction of that polarity change on the RF input which is changing at a different rate than LO (if the frequencies of LO and RF are different), that is when the IF output becomes the sum and difference of the LO and RF frequencies. Am I correct or am I in the dark corner???

[@scottp1100]

The LO is really biasing the top and the bottom of the RF port's transformer to ground. He drew current coming from the ring diode, but that's misleading (I think) because you don't really want current coming from the ring diode (it's really current on the RF side of the transformer coming from ground over there). Any current coming from the diode-side is likely LO leakage (The current from the RF should flow to RF, but a lot of LO leaks into the IF port - you can see it when you measure the IF port output on a spectrum analyzer. Mixers have bad isolation.). As the ground bias from the ring switches when each half of the ring diode turns on/off, that's where the RF port's polarity gets switched back a forth and adds/subtracts the LO to the RF frequency or the equivalent of a multiply (If you wanted to just add the RF and LO you could use a combiner, but that wouldn't get you 1/2(IF+LO) and 1/2(IF-LO). It would just get you RF and LO on top of each other). You need a strong LO stimulus power to turn on/off the diodes. The goal of the ring diode is to just grounding the top half or bottom half of the RF port's transformer - that's why other mixer designs sometimes use MOSFETs instead of diodes to turn on/off. Correct me if I'm wrong...

[@aero_pilot923]

I have a variable speed circuit board which has a Triac on the circuit board. The circuit board varies the AC ( 120 VAC line voltage) to control a carpenter's router. The motor blew. I need to check the circuit board if it too did not fail . Can a voltmeter ( which has no load) directly measure voltage ( or varied voltage ) directly out of a known working or non- working circuit board ( like that of a dimmer switch for a ceiling light) or does it need a load to measure - to see if a voltage ( or a varying voltage) is at its output of the dimmer ( or varying speed of a motor such as a router) ?? Thank you ... Maybe do a video on it

[@w2aew]

It depends on the meter. Only a meter that is specified for "true RMS" readings will read correctly. It also depends on the nature of the speed control circuit, whether it needs a load to work properly (most likely not, but worth mentioning).

[@researchandbuild1751]

What do you need to drive this mixer? How much voltage, and what kind of impedance does it expose to the driver side?

[@w2aew]

Typically about +7dBm drive when built with schottkey diodes. Impedance looking in will depend on impedances on the other ports.

[@thomasoffenbecher2196]

Excellent explanation, thank you very much.

[@gardoomforge8273]

An amazing explanation! Than you very much and keep up the good work!

[@andrewferg8737]

Question: I've built a diode mixer for AM modulation and compared it with the Gilbert Cell modulator. Does the diode version always suppress the carrier? or can it be adjusted produce a traditional AM signal like the Gilbert Cell?

[@w2aew]

You can sort-of do this by adding a DC offset to the baseband signal applied to the IF input.

[@peterfitzpatrick7032]

That 'scope is thirteen & a half grand (€) here in Ireland 😔☹ But at least I am blessed to have your teaching & demonstrations for free here on the Tube... for that I sincerely thank you !! 😎👍☘🍺

[@w2aew]

I am very lucky to work for Tektronix - so that helps!

[@cozycactus]

hello..can you do video about antiparallel diodes mixer? that works on half frequency of local oscillator

[@rsim22]

Fantastic video! - Any chance you can do a similar video on the JFET ring mixer?

[@tim46767]

Thank you for this great tutorial. But I have another question: How works a Polyakov mixer?

[@marcisberzins]

Polyakov mixer in his DC receivers works with large signal from LO (with frequency two times lower than the signal frequency), which turns on the diodes twice each cycle (one diode for +, other diode for -) and the RF signal, which is small, is sent to the output at these times. We have at the output the difference frequency between 2 times LO frequency and RF frequency.

[@Yureka-ox5jn]

You say that the point between two diode acts as ground. For the transformer (RF side) both ends can be connected directly to ground and no need to connect between two diodes. This should also work isn't? But then how does RF gets multiplied if the LO signal is not affecting the induction of second transfer? I think there will be a back emf from the first transformer and that will allow some charge to flow from point (between two diodes) towards second transformer and affect the induction level at that moment i.e. gets mix with induction generated by RF signal?

[@uygarglk]

Thank you for great explanation.

[@Arijit_VU3ICT]

Great.. sir please make a video on working of bfo. Also a video on total working of bitx20 by OM ashar farhan with tx and rx procedure. Thank you.

[@CH_Pechiar]

Alan, can you show us more in detail the mixer, ie, the hardware you buit? Which diods, etc. Thanks, CH

[@w2aew]

The details are on the schematic. Diodes are 1N5711 Schottky diodes. Transformers are trifiler wound on T37-6 cores. The previous video posted on my channel shows in detail how I made the transformers.

[@CH_Pechiar]

***** thank you.

[@Koolandonymous]

very helpful video ....alan. can u please simulate the same using any software.

[@RatedA4Aliens]

7:56 you mean IF output, not LO, right? Slightly confused as to what exactly is getting mixed and in what practical application this is useful. I thought the AM modulation is a result of mixing a carrier wave with an audio signal to produce the RF but here you are mixing an RF out with a carrier frequency, doesn't the RF already have some kind of modulation?

[@w2aew]

Yes, I meant IF output - sorry about that, I misspoke. AM is one application for mixers, but certainly not the only one. A *VERY* common application is for frequency translation - to adjust/move and RF signal from one frequency to another. This is the principle used in super-heterodyne radios. See my videos that are linked in the video description.

[@RatedA4Aliens]

@@w2aew Thanks

[@RatedA4Aliens]

@@w2aew 5:42 In the diagram on the right, shouldn't it be LO in the primary coil? Looks like a typo.

[@w2aew]

@@RatedA4Aliens Yes, you are correct, this is a typo.

[@MyWorld-sx2tq]

Do the undesired harmonics generate because of the diodes' nonlinear response?

[@sameersiddiqui7139]

Can someone explain what is the exact purpose of the two transformers used in the circuit?

[@w2aew]

The two transformers create a balanced differential drive to the diode ring. This is why it's called a double-balanced mixer, and why the carrier and LO are suppressed in the output.

[@dirkpeters9611]

very good explained. Thank you !!!

[@adilmalik7066]

is the leakage you pointed out in the spectrum the same reason we see "LO feedthrough" on spectrum analysers? excellent video!

[@w2aew]

Similar, yes.

[@khalidtarawneh2289]

that should give u harmonics at 3Mhz and 17Mhz not 13Mhz as mentioned at 2:07 73s

[@nevmarr]

Hi Alan. You comment that the IF output should have a good termination / a nice broad band termination, to prevent reflections. I’m all good with that. There is plenty of similar discussion on the web etc that agrees but “everyone” talks about a 50R IF termination. Is there something special about 50R or is it just a convention? Reading the comments I see the transformers XL need to be 4 or 5 times greater than RL … maybe 50R IF translates to a “practical” number of windings for homebrew transformers? Further, I assume the more XL the more attenuation on the ports, desensitising the mixer?? Thank you for letting me think out loud as I don’t have any Elmers etc to discuss with.

[@w2aew]

50R is commonplace, but not set in stone. Note that when making RF transformers, it is common to have the winding inductance be at least 4x the impedance used by the signals going through the transformer so that the inductance isn't really seen, but the impedance is then given by the impedance present at the transformer's input/output. More XL on the transformer windings helps to make the transformer more ideal - to a point. If you put too many windings, the interwinding capacitance will bite you. So 4x is the generally accepted minimum, and probably no more than 10-15x the system impedance on the high end. You can get away with a bit more - it all depends on when the parasitics start being a problem.

[@nevmarr]

@@w2aew Thank you for your helpful comments. You say the transformer inductance needs to be at least 4X so that the inductance isn't really seen … that initially confused me but after much thought I’ve concluded the RF transformer winding “being used” is in parallel with RL, AC wise, hence the total inductance is close to RL. Am I on the right track?

[@w2aew]

@@nevmarr Yes!

[@nevmarr]

@@w2aew Whoo-hoo!!! Once again, thank you sooooo much for taking the time to help me.

[@1bizjets]

Good refresher. Thank you.

[@charlieb.4273]

Why did you choose T 36-6 torroids as opposed to a type 2? I plan on building this and will use the T-36-6s but I am curious as to the choice. The permeability of the materials are close. How did you decide on the number of windings?

[@w2aew]

Quite simply - I had more of the type-6 on hand. As for the number of turns - I simply followed an example that was in one of my many books - probably Experimental Methods for the Radio Amateur, or maybe even the ARRL Handbook (sorry, I don't remember what book I borrowed the design from).

[@roylt21]

are mixers in general bi-directional? Meaning can I have my two inputs be both IF and LO ports, and look at the mixing products at the RF port? Or can you only apply the inputs to RF and LO, and have IF be the output?

[@w2aew]

In general, yes. Most often the IF and RF ports can be interchanged.

[@danmoos3635]

Is the first transformer's only purpose creating the phase split?

[@mrjohhhnnnyyy5797]

2:15 Dave's ruler, that's nice!