This channel is a real gem. Thanks for the video.

Fantastic work! And thanks for the shoutout :)

@DanielBogLab

7 ай бұрын

Yeah that Daniel guy seems cool

Them diodes

I’m sitting here in the middle of the night, suffering from paroxysmal coughing from bacterial bronchitis, and a Curious Marc video pops up and acts as a soothing balm.

@CuriousMarc

7 ай бұрын

Oh no! Our younger daughter went just through the same thing! Best wishes for a full recovery!

@TheMightyOmega-NotTheAlpha

7 ай бұрын

@@CuriousMarcmany thanks, they tell me 3-6 weeks, alas.

@CuriousMarc

7 ай бұрын

@@TheMightyOmega-NotTheAlpha Yes, same for our daughter. I shall make a few more videos to help out then!

Thanks for the explanation! I think that in addition to not having a calibrated timebase, your ad hoc sampling scope could just as well happen to have a negative timebase, i.e. the "trace" running from right to left. This reminds me of my first encounter with a very early digital scope during my thesis work. It didn't have oversampling, and I was dumbfounded for like an hour why my signal ringed _before_ the transition. Like, how could it know‽ Of course it turned out that I had the timebase set at ms instead of μs as intended...

@CuriousMarc

7 ай бұрын

Indeed, good catch! Yes, this completely lacks the trigger plus picosecondish delay control of the strobe pulse that you need to make a great sampling scope. That’s the tough bit actually. But I still found it fascinating to play with a sampler. To think that I paid $5 for that marvel of engineering!

It's interesting to see where else this sampling circuit pops up, the 8405A vector voltmeter is an obvious example (which has the added feature of phase lock sampling rate to the ref A) and then samples the B input producing two IF signals at around 20kHz for both A & B off which phase and amplitude measurements can be made (and the IF works just like a sampling scope and is available out the back - thanks HP). Then the 3406A random sampling RF voltmeter which removes the phase lock and just uses modulated sawtooths to control the sampling points and produces an IF which bears no resemblance to the original signal but which has similar statistical properties (like RMS voltage, although sadly the inbuilt voltmeter isn't true RMS, but once again the IF is available on the back). Finally in the sequence the 8410A/B/C VNA does exactly the same trick as the 8405A (albeit in two stages) producing a VNA up to 12.5GHz in the basic form and to 18GHz with selected mixer heads which is still useful today (and which isn't microprocessor controlled).

Very good video! I recently experimented with a sampler, managed to create nicely symmetric pulses that were below 100ps rise and fall time, and 2,5V in amplitude - I was so thrilled :) So interesting with circuits that are deceptively simple on a schematic, but so complex to realize in practice. Gotta love step recovery diodes and RF magic!

@CuriousMarc

7 ай бұрын

Awesome. I also enjoyed looking at this fellow’s project, he just recreates and tests all the circuits with components he has lying around. Turns out it works with fairly common diodes too, just not as fast. His blog is well worth a read: hackaday.io/project/162998-the-rise-and-fall-of-pulses/log/158851-a-toy-diode-sampler

@arrbam02

7 ай бұрын

@@CuriousMarc yes!! I read that project blog thoroughly a lot of evenings along with pulse generator research PDFs and part of my sampler experiments used ideas from that hackaday project.

This channel rocks. 👍

Schottky diodes, field effect transistors, forward voltage, pi network, source follower. The part of me that wishes I had pursued electrical engineering over industrial engineering loves these lessons in circuit design.

@W1RMD

7 ай бұрын

After 27 years of being a heavy truck mechanic, I up and quit and started training in electronics.

Very cool. I couldn't figure out the snub circuit, but your explanation was clear

Now I get how the sampling ciscuit operates, last video left me out in the cold. Thanks a lot for taking the time and explaining it.

@CuriousMarc

7 ай бұрын

Yes, I intended at first to have it all in one single video, but that became way too complicated.

The principle of the shorted stub is explained in more detail in the manual of the hp8551 spectrum analyzer. (Impulse forming for the PLL, sharpening the output of step recovery diodes) I repaired on many of these instruments more than 30 years ago.

I think the same idea is used to down-shift frequencies in digital frequency counters. In 80s, the digital circuits couldn't go faster than 100MHz. I learn this in my sophomore year and i couldn't quite understand how it works. Thanks for explaining it.

@KallePihlajasaari

7 ай бұрын

When the shape is not important often easier is to square up the input and then use digital dividers/pre-scalers or mixing/heterodyning to measure frequency which is what the Nixie frequency counter is doing with most of the other plug-ins.

A lightbulb moment! thanks

So that's what a sampling scope does! I read about it in the manual and always wondered how it may work. Now I know aliasing can actually be used in a constructive fashion and learned that the most entertaining way. 🙂 That is invaluable, thanks a lot!

Thanks for the video now I understand my sampling scope better.

Thanks for a blast from the past. One my early summer jobs was debugging part of a high speed circuit for a high energy physics group. I'm a bit vague on the details after so much time has passed, but I recall tunnel diodes and a short (about 30mm) piece of coax shorted at one end to get a delayed and inverted pulse. I used a Tektronix 661 scope with (probably) a 4S1 plugin. I recall always having to be wary of aliasing. Ordinary analog scopes in those days weren't even close to being able to show a real-time trace for such fast signals.

@paulcarboneNY

7 ай бұрын

I picked up a working 661 & 4S1 a few years back, it really is an amazing instrument, as specially considering when it came out. The construction & documentation of those 60s era Tek scopes is like nothing else.

Another great video! Thanks Marc!

It would awesome to see a simple-as-possible diode sampling circuit built Manhattan style.

@CuriousMarc

7 ай бұрын

Your wish has been granted: hackaday.io/project/162998-the-rise-and-fall-of-pulses/log/158851-a-toy-diode-sampler . That's the simplest working implementation I have seen.

RF dark arts, nice lesson & explanation

Just when i thought i knew a lot. Someone shows me i know very little. That was a great lesson.

Don't ask what your scope can do for you, ask what you can do for your scope. For instance increase it's resolution by a factor of 50. 🙂

I do love watching your videos. I'm a truck driver so I probably only understand peko bit of what your saying but I do find it fascinating. If you get time could you explain why counting frequency and sampling is so important?

@CuriousMarc

7 ай бұрын

I'd be happy to oblige. So many uses for frequency counting, but the primary one is for radio signals, radars, and cell phones. All that radio technology is based on stacking frequencies and modulation, and the more stable and precise, the better. Perhaps the most ubiquitous use of super high precision time counting is in your GPS receiver. The GPS transmitters are actual atomic clocks flying above our heads, and you triangulate your position by measuring the time difference from clock signals that you receive from different satellites. Sampling has also many uses. First for its original application, which is sampling scopes that I demonstrate in this video: to measure signals that are faster than you can measure them by normal means. It allows you to slow them down. There are also radio applications, as mixers to shift your received frequency down (same idea, slow radio signals down on the receive end so you can amplify them easily). But the most important use now is digital communications, wired or wireless. Within your computer, in the internet, in your cell phone. To receive a bit, you continuously sample the received signal, and adjust your decision point ("is it a 1 or a 0") based on centering the sampled signal. In essence, the latest computer chip high-speed bus pin or Ethernet receiver have what amounts to a mini-sampling scope built-in that continuously monitors the signal and adjusts the receiver. Your phone data demodulator does that too.

@direstraits05

7 ай бұрын

@CuriousMarc Thank you. That's outstanding.

@glennmayall5461

7 ай бұрын

Sampling is also used in the reverse direction to convert analogue signals into digital signals i.e. speech and music. For speech in telephony systems, the analogue signals, say from a microphone, are sampled at 8khz. The resulting sample is converted to a 8 bit digital value via an analogue to digital converter, thus creating a 64kb/s bit stream. For CD quality music, it is the same principal, however it is sampled at 44.1khz and converted to a 16 bit digital value. This results in a 44.1khz x 16 x 2 (for stereo) = 1441.2kb/s bit stream.

@W1RMD

7 ай бұрын

We didn't have these signal sources flying over head back in 1968.@@CuriousMarc

This is gorgeous!! A few weeks ago I bought a cheap USB Oscilloscope, and have been wondering how to give it a speed boost. Even got far enough to see diode sampler circuits but I had no idea how they'd work - your explanation is the first that made it crystal clear, thank you so much! FYI, the 'scope is an Analog Discovery 3, with 30MHz bandwidth and a lot of decent I/O ports. Shouldn't be impossible to use modern components to create triggers on the HF signal. You can even get configurable delay line components in the ns delay range for barely more than 10€!! Beautiful stuff :D

Woot new video!

Wow, this was like top notch voodoo in the 60ies, still holds up today. It's slowly getting accessible to the average crowd - with average I mean the guys who do RF stuff, still a minority of population. But you don't need a governmental organization for example to do x-band nowadays. Exciting stuff!! I got a 6GHz 120MHz BW SDR, but they made a hack that uses harmonics to give you a max. RX frq. of 30GHz as an option, for bargain, really almost free. It's not super calibrated in this mode, but it freakin works. No ad here, I'm just amazed of that thing, it's from Aaronia.Spectran V6.

RF Electronics is alien magic. 🙂 Great video Marc, thanks for posting!

Very impressive

I love this so much

Woah, I had no idea those counters used the same sampling techniques as the equivalent time sampling scopes. I've been on a 1960's Tektronix sampling scope tear lately, and have fixed a bunch of plug-ins and sampling heads. cool stuff!

非常清晰明了，谢谢❤

amazing

"The one weird trick Nyquists hate!" haha

Ohh now I need one for my 5248L!

Great demonstration, very satisfying. Your explanation of this method, again with elevator music, is nothing less than prestigieux. You should become a university professor due to your intelligible lectures.

This is fantastic thanks! The electronic equivalent on an autocorrelator (more or less)! Is it possible to measure rise time and pulse width of a sub 100hz repetitive signal with subnanosecond duration with it?

It seems simple when you explain it. But I marvel at the people that originally came up with the math to create these things. The difference between magic and technology is knowledge.

@CuriousMarc

7 ай бұрын

No kidding. I marvel at them too.

So we'll explained.

The trick only works for periodic signals with limited frequency bandwidth in baseband.

Wow

Aren't Keysight direct descendants of the HP?

@DrFrank-xj9bc

7 ай бұрын

Nope. HP => Agilent => Keysight. Always the T&M stuff got transferred.

@deepblueskyshine

7 ай бұрын

@@DrFrank-xj9bc Aren't you direct descendant of your two grandmothers and grandfathers?

@DrFrank-xj9bc

7 ай бұрын

@@deepblueskyshine Not directly. Grandfather => Father => Son. So, are you? There's a logic riddle, that results into that you are your own grandfather: Stay tuned for the next episode. 🤔 I can't fully judge that case, but I may ask my daughter, what she thinks about her 99 y/o grandfather.

@CuriousMarc

7 ай бұрын

Yes they are! They are the true heirs of the original HP. They should get their HP name back! If you go visit them, the engineers’ labs and cubicles are filled with old HP instruments, just like my lab!

@deepblueskyshine

7 ай бұрын

@@DrFrank-xj9bc Yes, it's a matter of culture and judgement without written law. It reminds me of a vague analogy: in web textual markup standards language is defined by duplets i.e. en-gb, en-us which developers call culture which in terms isn't exactly the regular notion of the term culture. Or, yet another riddle: your family name is of a famous historical person and indeed you belong to the same family, and you together with your second or third couisin are descendants of that family, but your grandfather is that famous historical person, and your cousin's grandfather is that person's brother. Who of you is a direct descendant of that famous historical person?

It's quite like a mixer circuit.

Marc, don't be sensitive about your English pronunciations. In Inland Northern we have a way of pronouncing words differently than anyone else, especially place names like Milan (long i), Toledo (long e), Gratiot (rhymes with sh☆t), Bolivar (sounds like balliver), and many other Midwestern toponyms large and small. If you attempted to conform to one English dialect you are liable to offend all the others.

Is this similar to aliasing on the input side?

Couldn't you use the trigger output of the pulse generator as the external trigger for the scope to improve inter-sample jitter?

👏👏👏👏👏👍

Would’nt the “cheap” 100 mhz scope aliases by itself a higher frequency signal beyond it’s sampling rate?

@stargazer7644

7 ай бұрын

No, because the signal won't make it past the scope's front end. The amplitude steadily decreases to nothing as you exceed the scope's bandwidth.

kool

Hi what is the main difference between 2diode 4diode or six diode samplers???

Hi Mark I have got such a transfer oszillator but unfortunately these Shottky diodes are toast in my case. Do you know closest replacement of current available diodes?. Could not find a data sheet as there is only a HP type number given in the service doc. Do you know if the attenuator should also handle DC as the drawing suggests? Probably mine is also defective as it shows infinity resistance. Thank you and congratulation to your outstanding and amazing channel

@CuriousMarc

4 ай бұрын

Although any modern Shottky that can do 20 GHz should work, the big problem is to find one with the right diameter and length tubular package, not sure if they make these anymore! HP made most of their microwave diodes available commercially, but under a different HP commercial number (5082-xxxx) or plain JEDEC number (1Nxxxx). I have not looked for an equivalent, but maybe take a look at a vintage HP microwave semiconductor catalog (the 1980 RF Diode and Transistor Designer's Catalog is online). Then maybe see if you can find one on eBay. Or get a modern Shottky and jury rig a mount that fits. The input should measure 50 Ohms at DC.

@jps-ib8vh

4 ай бұрын

I looked through available historic documents but could not find a JEDEC number. I think I will try a 1N5712 which has a low capacity of just 1.2pF. Interestingly they used rather long ( 10cm +) wires to R1 and R2. Maybe this works as an inductance ? I would rather suggest to have R1 and R2 more close to the diodes/ 2pF capacitors. I will report further progress here but this will take some time until I have got the spare parts@@CuriousMarc

@jps-ib8vh

4 ай бұрын

It turned out now that the sampling diodes are ok. I tested them falsely defective because the diodes have a 2k2 resistor in series. So diode testing gave a wrong reading However the attenuator has high impedance in all branches and the 50 ohms resistor R1 seems to be also gone. The attenuator showed destruction from high voltages, I could not locate R1 physically as I do not want to disassemble all the RF part. to be continued,,,,

@CuriousMarc

4 ай бұрын

@@jps-ib8vh Well that's good news. 50 Ohms surface mount resistors are far easier to find and change than weird RF diodes! I'd try to disassemble the RF part and get to it...

@jps-ib8vh

4 ай бұрын

@@CuriousMarc Hi Mark, I found a detailed description of the sampler in the hp journal 1966-10.pdf pages 12 - 15 ( could not post the link unfortunately) It is a true masterpiece of microwave engineering. There is also a name and a picture of this amazing true genius: Wayne M. Grove. Now it is very clear that it is impossible to replace such sampling diodes by modern types. They used a very special three terminal design that includes the sampling capacitor. Before I found this article, I tried to get the sampler out for repair as there was no 50 Ohms resistor detectable. But by opening the golden union nuts on the sampler block the inner conductors starts turning and immediately destroyed the tiny golden spring that is micro soldered to the two cones of the inner conductor. So NEVER EVER open these nuts. You get the sampler out by removing all pcb´s and the bigger golden union nut connecting the attenuator. This nut is hold in place by a circlip that is very difficult to remove. The broken 50 Ohms I found under the chrome plated terminal cap. It looks like the attenuator and consists of an aluminium oxide subtrate with thin film metalization . It was also fused. I replaced it by soldering 2 times ten 1k 0603 resistors in parallel that I soldered on a self- adhesive copper foil. Currently I am struggling to replace the destroyed tiny golden spring. Unfortunately, I do not know exactly how it should look as I could retrieve only some fragments. To be continued…

Is there a link to an online version of the article show at ~3:20?

@CuriousMarc

7 ай бұрын

It’s not available for free, but you can purchase it at semi reasonable cost from the IEEE Xplore library. It’s an extraordinarily good article, and its reference section is encyclopedic. Here is the link ieeexplore.ieee.org/document/1201815/

@NathanGibbs3

7 ай бұрын

@@CuriousMarc Thank You. 🙂

@CuriousMarc

7 ай бұрын

@@NathanGibbs3 Edited my response to include the link.

@NathanGibbs3

7 ай бұрын

@@CuriousMarcThank you again, links to IEEE documents may be a good thing to put "down in the doodle-lee-doo" when referencing them in your videos. 🙂

@CuriousMarc

7 ай бұрын

@@NathanGibbs3 Not this one. It's not freely accessible, and not cheap either mind you, it would make people very angry. But believe me, it's worth all the money.

I came to this video because I want to make some circuit for showing a signal up to 10 Mhz on a PC-based oscilloscope. There are several free oscilloscopes that run under Windows and even under Linux, but they require a digital interface that some people have made with Arduino. However it is possible to view low frequency audio signals directly through the microphone connector. The problem is that these signals can rarely exceed 2 or 3 Khz if you want to observe them correctly. A rectangular signal of only 10 Khz is impossible to observe on a Windows based oscilloscope, entering through the microphone connector. I have already done it and the signal, far from looking rectangular, looks totally deformed. That is why I came to this video. I want to develop a small interface that is able to take samples of a signal higher than 1 Mhz and transform them into an exact copy of the original signal but with a frequency 1000 times lower, in order to display it on a Windows based oscilloscope. I hope to achieve something....

@CuriousMarc

Ай бұрын

Interesting idea. At these frequencies, what you need is called a sample and hold circuit.

HF engineering is completely bonkers. I mean, shorting your circuit to ground to make the signal even better... 😲

If the Vfs are just cancelled out anyway may I have one for being the 4th comment?

@CuriousMarc

7 ай бұрын

What a nice way to ask! You are awarded two canceling Vfs, and while we are at it we’ll throw in the canceling strobe kickouts.

@kaitlyn__L

7 ай бұрын

Aw man, Whiskey Tuesday always gets the kickouts

@whiskeytuesday

7 ай бұрын

@@CuriousMarc It must really be my lucky day!

@whiskeytuesday

7 ай бұрын

@@kaitlyn__L Destructive interference so annoying that it gets a special name is meant for sharing, free kickouts for everyone!

Tsk, tsk, tsk! Elevator muzak is usuallly Girl from Ipanema... ;)

I'm the operator of a transfer osilator

@user-sd3ik9rt6d

7 ай бұрын

By holding down a special key it outputs microwave frequency

I seem to recall that the old Tek 465 'scopes have tunnel diodes in the front-end. They use quantum tunneling to effectively achieve negative resistance, apparently. The things that happen up in the gHz range are strange indeed, it really is like magic.

@CuriousMarc

7 ай бұрын

Yet another kind of weird diode, different from the Shottky and the Step Recovery diode. The tunnel diode is a fast bistable element, used in trigger circuits usually. Also to make microwave oscillators. It does use quantum tunneling indeed!

@poofygoof

7 ай бұрын

@@CuriousMarc My father-in-law worked on sampling heads for the 4S2(A), S-4, and others at Tektronix in the 60s. He has stories about how expensive and small the tunneling diodes were and how the engineers were paranoid of losing them on their benches. :)

Wow