#1181

Episode 1181
Why is there a coil of wire in my oscilloscope?
Be a Patron: / imsaiguy

[@johnwest7993]

All cables have a 'velocity factor', a speed noticeably slower than light, at which the electrical signal travels through a medium such as a cable. All RF cables, ladderline, windowline, coaxial, twinaxial, and triaxial have that speed specified for that type of cable, so a delay line is just cut to length for the amount of delay desired. Most RF coax's have a velocity factor of between .66 and .88 of the speed of light in vacuum. Using that knowlwdge is a great way to design antenna arrays in order to get the phasing right. . Who would have thought back when I was working at HP building scopes that 50 years latter I'd be watching KZbin videos about their delay lines?

[@robbylock1741]

The exact term is velocity of propagation, back in the 1980's I worked on a project that used a coiled semi-rigid coax cable delay line, very cutting edge at the time.

[@fredmitchel1236]

How much slower....? I heard thru coaxial cable is maybe 2/3 slower...than the speed of light in a vacuum... If speed of light in a vacuum is close to 2.998 x10e8 m/s...then that is about 1 foot in a nS... Then say in RG-58 A/U will be little less than 8 inches per nS... I wonder when the type of coaxial cable is changed like to RG159...or that little like SMA Lucky our trusty O-scope can measure the delay..... Such as if you scope is calobrited...the marking are wipe off or missing....and the cable has continuity....then measure its delay... It is kind of amazing...to just use some cable...for the delay... Probably now...the is a 16 pin solid state delay chip...you just send it some digital ...then ALE...boom...the delay performed.... Ok Fred..but you must preserve the wavewform...so maybe some sample and hold ...idk Essentially having like many different delay times seems like it could be done with a few chips And IMASI Guy approximation of 9" per nS is close.... All I had was a first google hit...to hear about the approx speed of electrons thru RG-58... I predict...but I am have been very wrong.....because you have had lots of experience... I think say the speed thru say 75 ohm coaxial cable would be close to the speed of a 50 ohm cable... Maybe the speed is just dependant on using metal wires....and the dielectric... So I busted out the ARRL antenna book...and started digging.... Here are some nominal VF of commonly used transmission lines... First a few with polypropylene..foamed...like little air bubbles..FPE VF Rg-8 -86% Rg-8x 86% When solid polypropylene 66 %... I thought Teflon might be better...69.5%... Open wire line had the best 92%...no dielectric RG-58A Why is the speed slower through coaxial cable ...compared to light traveling thru a vacuum? Another topic to enlighten myself with Which then might be 8" traveled in 1 nS... Amazing... I wonder if it's because the electron moves in a helix or spiral... Rg I have no idea but can look it up... I thought the dielectric might slow down or have a loose like in some dB per kilometers... It seem the speed of the conduction has a lot to do with the permimily

[@fredmitchel1236]

Thanks to our readers...lots to be learned...

[@robbylock1741]

@@fredmitchel1236 It varies by choice of dielectric material, I worked with some PTFE and Teflon materials, some with as high as 85% VOP

[@rjordans]

The speed difference is from the difference in dielectric constant of the insulator material. The speed of light in a material is C=1/sqrt(mu*epsilon), if you change epsilon things slow down.

[@katough]

KZbin is like, we saw you watched someone build something using a soldering iron, here's a video about 40-50x more complicated than that.

[@IMSAIGuy]

I also have some really simple and boring videos of me building a kit with a soldering iron. kzbin.info/www/bejne/aaDcfYipj7Wkd9k

[@derkeksinator17]

If you want to step it up even more, check out "The Signal path", you'll be none the wiser, yet in awe of the nice equipment.

[@hoofie2002]

There is a trading exchange in Chicago that uses large drums of fibre optic cable to put a delay into their network systems so they don't get a subtle advantage. Mandated by the SECC.

[@lmamakos]

Reminds of the DIP-14 sized delay lines on the S-100 bus DRAM memory boards I had. They were used to generate the CAS and RAS signals to latch the address into the DRAM device. Those were somewhat smaller than what you're exploring here :-)

[@IMSAIGuy]

I had forgotten about those beasts. lots of dubious timing circuits in those days. one shots and delay lines.

[@absurdengineering]

@@IMSAIGuy They had the right idea, in a fashion: asynchronous circuitry. It works better on a chip, though, since everything is on one die and the delays age similarly and similarly react to voltage changes. I guess the delay lines were cheaper than a bunch of gates in series? Especially CD4000 gates can give you lots of delay and lots of rise/fall skew quickly :) One-shots with RC timing do their own thing with temperature and age. I have had some luck just putting enough gates in series, or even a long differential pair going a couple times around the board - and back then some boards were plenty big :)

[@packratswhatif.3990]

What a sweet setup. Id be keeping that little gem as a reference test unit. Gotta love the old electronic stuff.

[@dingusnutts]

I had just read about SDL, spiral delay lines used to make traps for a multi-band antenna in a Nov 1972 QST. This stuff is fascinating. Thanks for the video.

[@alklapaxida850]

this type delay is also used to phase antenna systems, nice video thank you.. regards from VK3

[@IMSAIGuy]

It is also used on atomic bombs to detonate the high explosives all at the same time.

[@Curt_Sampson]

@@IMSAIGuy This system was also used, in a sense, in the data centre where I had a system running a high-frequency trading application back about 15 years ago. Some racks were further from the exchange system than others, but everybody was wired to the exchange with the same amount of cable so that the folks physically closer to the exchange didn't get an advantage.

[@egbertgroot2737]

Great topic! I immediately stopped al my other activities to watch this. Thx

[@DonzLockz]

Very smart dumb luck guess! :) I learnt something today.👍

[@TeslaTales59]

Very cool method of delay. Reminds me of those springs in guitar amps used for delay and echo.

[@johnwest7993]

Called reverb springs

[@applanateearth586]

I haven't got 50 nano seconds to spare...I'm busy!

[@fredmitchel1236]

Your the best...great demo... You accomplish so much Cool...and explained perfectly & guessed and measured accurately I am glad you reused & harvested some that HP & made short work of it two.I hope the beefy multiple tap power transformer was saved... This kind touched and sort of opened the door to visit to TDR land I think I am hearing...input comes in to vertical amp and or attenuators- if signal is high voltage ..that vertical signsl then split...one path delayed then amplifed for the vertical screen The pre split also goes to the trigger for needs 55 nS to create process and create the trigger sweep.. And to see a trace a little time before the rising edge ..the trigger sweep propagation must a little time faster than 55 nS I only yapped here to demo that I can learn and comprehend a tiny Ah one more comment to go...for IMASI Guy...on Test Equipment... I was in that wavelength and synced to the IMSAI Guy It was Jim Williams I was trying to remember...it seemed he has some books out...I saw he had some old KZbin teaching before passing away...I.looked at CE amp instability and how to cure ....But his KZbin desktop and workbench was uncharacteristically....immaculate.. maybe at that time...management said...sure Jim...you can use our test equipment to create some lessons...but please show a neat work bench....lol... Good old Bob P....Almost bought his book at Frys Electronics San Jose Now our Phx Frys....an empty shell...

[@jagmarc]

These DL are brilliant for triggering a scope before the event you're looking for, so you can see what was going on before the trigger point

[@derkeksinator17]

Yes, not neccesary today, but it was a really nice feature back then!

[@treelineresearch3387]

Subbed as soon as I saw the Dymo sticker on the Rigol model number, did the same thing to mine after I flashed it to the better model!

[@PsRohrbaugh]

>measures in mm >estimates in feet 😁

[@technishn]

That brought back memories. Over time they used to physically sag and affect the response.. Guess the weight of the top squeezes the bottom turns..

[@jafinch78]

As simple as they are, I thought was the neatest device to tune phases when I first learned about. Still seems neat to me and the analog world is just like that being more natural physical properties of materials (mass & energy). Working my way towards the Prius CVT 3-phase alternator/generator/welder/plasma cutter, I've acquired a few generators to study hands on the designs and recently was thinking about the easiest ways (without being huge) to phase sync two smaller like 5000W generators that are the older analog synchronous generator designs... with no solid state controls and pretty much just the carb. I figured so far... simple mechanics of setting the positions of the stator/rotor and using one engine on a pulley/sprocket/gear for each. Now, if using two separate engines... thinking will need some RPM and idle controls... or like maybe some sort of tune able delay like would be nice which I've seen in microwave devices with like a telescoping delay line design.

[@luminousfractal420]

Your coil maths and measures 🤣🤣🤣

[@billelkins994]

Now determine the time delay using a grid-dip meter.

[@byronwatkins2565]

1 ns/ft in vacuum. In coax it is about 1.5 ns/ft depending upon the coax.

[@goosebyte]

how does a vacuum make it faster? If this is the matrix, i wonder if each air molecule is an object that slows the simulation?

[@byronwatkins2565]

@@goosebyte A vacuum has lower index of refraction (permeability and permittivity).

[@tfrerich]

Thanks for the explanation. I knew there was a delay line--mainly because it tended to be identified in servicing photos of the inside of the 'scope--but I never really thought about what it was used for. (I don't want to give the wrong impression. I used 'scopes; I didn't service them. Contrary to a number of assertions, real engineers DO occasionally read manuals, generally because they didn't earlier and should have.) That delay line looks like a nice balanced transmission line. I wonder what its true characteristic impedance happens to be. I'll bet if you fed and terminated it correctly that the signal distortion we see would be even less.

[@johnwest7993]

RTFM Read the fine manual. :)

[@t1d100]

Interesting. Thank you.

[@HL65536]

So that's why I can see stuff a few ns before the trigger. But I did not see any coil when I opened it last time. Gotta open it again now and specifically look for it.

[@jspencerg]

What's the impedance of that unique wire arrangement? Would this wire arrangement be an improvement for antenna feed line over coaxial or ladder line? Of course it would need an insulated sheath.

[@vvdvlas8397]

Линия задержки в осциллографе произвела революцию, позволив "заглянуть в прошлое" фронта или спада наблюдаемого импульса! The delay line in the oscilloscope has revolutionized allowing you to "look into the past" of the edge or fall of the observed pulse! Если я не ошибаюсь, то это придумали инженеры TEKTRONIX ~60лет назад. If I'm not mistaken, TEKTRONIX engineers came up with this ~60 years ago.

[@matthews4159]

Look on KZbin for " The Origins of Delayed Timings on Oscilloscopes - Workbench Wednesdays " I thought THIS was what Delay lines on analog scopes was used for ZOOMING IN ON REPETITIVE WAVE FORMS,, like video for example

[@IMSAIGuy]

the delay is a circuit that triggers the scope delayed from the main trigger, then the second sweep is at at different sweep rate. the delay line allows this arrangement to 'see' before the trigger. it would still work without the delay line, just you would not a able to see before the trigger, but you could still zoom in events after the main trigger.

[@CraftMine1000]

Basically, really temporary memory in the form of a slab of copper

[@Homer19521]

I thought it was an Ugly Balun.

[@dcmoisan]

My HP1722 has one of the delay lines tucked into it. It's still my daily driver.

[@frankowalker4662]

Clever stuff.

[@terrybondy5458]

The need for them now seems obvious now that you have explained it. Thanks. I know analog TVs also had a delay line, but the one I examined looked nothing like that. More like a small slab of glass with some angular cuts and I assume a couple of transducers. I wonder for what reason they are used in those?

[@dcmoisan]

PAL TV sets had both kinds of delay lines, ultrasonic and inductive. Ultrasonic (glass) delay lines were in most VCR's--they provided duplicate TV lines in case of dropouts.

[@BD-cm7xc]

I believe delay lines were for secam only systems. PAL and NTSC didn't need delay lines. SECAM differs from the other color systems by the way the R-Y and B-Y signals are carried. First, SECAM uses frequency modulation to encode chrominance information on the sub carrier. Second, instead of transmitting the red and blue information together, it only sends one of them at a time, and uses the information about the other color from the preceding line. It uses a delay line, an analog memory device, for storing one line of color information. This justifies the "Sequential, With Memory" name.

[@ovalwingnut]

Like my great nephew use to say... "That there is some good stuff, sonny." i.e. though provoking. Seriously, I didn't fully grasp - from end to end the fundamentals of DL's. I wonder if that's another overlooked (secret) component to be utilized, Like Mu Metal. Very COoL. Thank you! p.s. Like the "fade away" close.. Not sure why :O)

[@samuellourenco1050]

It is a good analog memory. :)

[@atlanticx100]

There used to be delay lines in old TV's.

[@ernestb.2377]

I am just reading in the AoE (Art of Electronics), the part about scopes, and read "all good analog scopes have a signal delay line". Ok, interesting. I know analog scopes often have A and B sweep, and B sweep can be triggered again (delayed), but that is not the same I think... As everybody always say, 'you can not see before the trigger' you actually can. If we use the external trigger input and feed it with the actual signal, then delay that signal and feed it into one of the regular channels we can actually see the part before the trigger. There should be a more compact delay components? Were they not used in the old TV's? Maybe they are not applicable, but in any way interesting topic for the vintage equipment users 😀 I will get tomorrow and old blown up Tek 2445 that I will try to resurrect back to life. I have 2 more analog scopes 20 and 60 MHz, just for fun. Enhancing those would also be fun thing to do. One idea is to use CH1 output (of the back of the scope) and connect to a self made counter, to automatic display the frequency, as a way of automatic measurement.

[@benrasmussen9878]

very cool, old school method of phase shift?

[@BOT_0x76DE45AB]

Don't try to follow that maths in the first couple of minutes. Somehow two wrongs made a right, but probably thanks to back-annotation.

[@bborkzilla]

Looks like the one that's in my HP 1710B

[@csimet]

Not unlike what we in the optical world call a launch cable. An optical launch cable is used in OTDR testing so the meter can properly register tests on shorter runs of single mode fiber (9 or 10µm typical) and is usually a few hundred meters in length. Short cable runs may not have enough length to allow the test meter to measure properly and within its parameters, as well as test the first connection of that cable. You can enter the known launch cable length into the meter so it knows where the actual test starts on the cable you are measuring.

[@IMSAIGuy]

I used to wrap a fiber around a pencil for a mode scrambler

[@csimet]

@@IMSAIGuy Attenuator. ;)

[@ejonesss]

would it work for sound? could you emulate stereo by feeding one channel through the coil of wire and get enough to emulate stereo?

[@IMSAIGuy]

should be usable. you will need to build and good circuit to drive the cable (and capacitance).

[@ejonesss]

@@IMSAIGuy i thought wiring the coil in series like you do with a resistor to limit current or an inductor to act as balast in some light bulbs

[@MadScientist267]

It's a good thing I have decent intuition... This was 🤦‍♂️

[@GrafRucola]

Veritasium wants to know your location xD

[@osvaldimar132]

Time Scall

[@shanieboi86]

Lol show this to veritasium

[@ahbushnell1]

1.5 ns/ft

[@tissuepaper9962]

Depends on the cable.

[@MichaelKingsfordGray]

Too many "umm"s for my liking. Less than 30 seconds in, and already five perseverations.

[@IMSAIGuy]

you had better run now, it doesn't get better

[@paulgrodkowski3412]

Are you guys nuts? How can this be fun? i heard that big companies, that make all of that technology, are vicious organizations! Is it good or healthy to do that stuff?

[@IMSAIGuy]

As with all organizations, there are good ones and bad ones. I've worked with great ones and have quit not so great ones. I'm retired now but lots of my friends still working are still having fun.

[@paulgrodkowski3412]

@@IMSAIGuy thanks for getting back to me so quickly! I stumbled on your KZbin video here on the internet and saw the different equipment. I find electronics interesting and started reading the Radio Handbook when I was a teenager. I liked reading about radio electronics when I was in Florida, in the U.S. Then I maved to Toronto in Canada and went took some courses in electronics at a commnity college. Always interesting ! I wonder if there are community colleges in Forida where I could learn electronics. I still think the approach to learning electroincs in America could be different and better in America than in Canada.😊

[@IMSAIGuy]

@@paulgrodkowski3412 learning is up to you... kzbin.info/www/bejne/eJjVppWta6eSq9U kzbin.info/www/bejne/hXOxnWBso6usgpI

[@paulgrodkowski3412]

@@IMSAIGuy thank you!😊