#199 

some of the best electronics videos on youtube. Really much appreciated.

Thanks again! I love your videos, they're a highlight of every day when they come out. I'm an Audio/Synth type guy, and I love that your knowledge is transferrable to audio rates as well as RF!!!

I can finally measure my FM air coils. Thanks again! Your circuits ALWAYS work! Tweaked it a bit and it runs fine in UHF. Quite accurate after accounting for the parasitic capacitance of about 10pF.

you never stop amazing me, i am just getting started as a hobbyist and i cant believe how much money it takes and now i have found something that is going to be my first project. thank you so much for sharing and being easy to understand. inductors are in almost everything. you are a hreat teacher.

Mr. Wolke, your channel is easily among the my top 5 on youtube. I love the content and the way you present it, you have a very good way of bringing information across in a clear and enjoyable way. Thank you, looking forward to nr. 200...

After searching for an accurate home-brew inductance measurement circuit, I built the circuit you described back in 2015 on RU-vid. I use my oscilloscope to measure frequencies. I am astonished at how close the measured frequencies are when compared to the calculated frequency, an average difference of only 1.14% across an inductance range up to about 3 nanoHenries. Thanks for sharing the design.

Really well explained. As a radio ham with no electronic training, this was easy for me to follow and useful. Thanks.

Very useful little tool. Great informative video, thanks w2aew. I copied your version on a bread board and it worked first time. Now to find a project box an sanitize it

I know it has been years since you posted this video but gold nuggets can be found all over and years old. I used J112s and this circuit works great. I just built the box and now I have an IF can tester (IF Transformer for those that don't like the term can). I found that oscillations are not stable on IF cans that I found to have SMD. I am going to work this as an issue and see if I can use this to spot SMD in old IF cans with reliability. As usual thanks for your postings and work.

Thank you so much. It's much easier to watch at the direct experience of an expert as you.

Fascinating video as always, on a similar vein by father built a small logic chip based oscillator into a box with a crystal socket. Was a super handy way to test crystals/filters.

I had just wound some toroids and was wanting to test for inductance.... Now I can build another "test circuit" to accomplish what I can do by breadboarding the toroid with a known resistor and check with my mulitmeter, and do the calculations by using my "brain box." I will make the test circuit later. I enjoy your channel and learning about radio electronics! Thanks for posting. 73's de KD5SMF

I built mine this morning, happy to report it sings happily at 9v, really pleased with it. cheers Alan. Paul m0bsw

As ever Alan, you deliver great tutorials!

Another excellent lesson Alan, thanks.

Nice little test circuit. Good video.

W2AEW de WU2D - great stuff Mr. Nomograph!

Nicely done. I've been trying to get the time to watch this since I received the notice of a new video.

Love it. Keep them coming.

I found the archive of the '73 magazines with an easy Google search, and finding the September, 1990 magazine and the specific article was easily done. It was worth reading, too.

Its good to see a predicted or calculated resonant frequency of a tuned circuit on the oscilloscope for confirmation if it is right.

Nice circuit. very useful. I use something similar for power electronics, mine uses a power FET, power resistor and square wave generator (555 timer) to obtain the current ramp characteristics and inductance of a inductor using a scope. This one seems to measure unknown HF coils.

Now the IBM Deep Blue just crying on the calculation speed of Your rulercalc :))))THX! Good video again!

Enjoyed, and it got me thinking. 73s de VK6BIL

For jean pierre daviau - yes, the 0.04 is in uF. The value is not critical. I think I used 39nF in my circuit, or maybe 47nF. All of the caps are ceramic, non-polarized. I added the 2.2uF cap as a power supply filter cap - not shown in the schematic. It goes from the power supply connection to ground.

As always, well done!

Again a great tutorial !

Realy great just what i was looking for Thanks

Something about coils and frequencies.... sorry I was transfixed by that glorious MDO3104 on your bench :-) Great video, as usual, Alan.

Very interesting... will refer to this when teaching radio class for acquiring amateur license.

Hi, Would a 2N3819 be a valid replacement for the end of line 2N5245 shown on the schematic? Do you have a suggestion? and thanks for your excellent videos, jpd

I love the content of your videos. However, how would it work with step response of LR when R is known? Form time constant one can easily calculate L.

New to this, this is an awesome tool!

wow, thx for the info and links! very cool.

Another great vid Alan. I sometimes come across a small transformer (eg., in a SMPS) which I want to determine if a winding is open or shorted. I've seen "ringer" testers for this purpose. Can you show us a DIY technique to this same end? Keep up the great work!

Nice work, is there a way to determine what guage wire, total length and how many turns one would need to obtain 50 amps and 24 volts from a single coil if the magnets are 60mm by 200mm rotating at 6000 rpm?

well done, good audio and video..

Great Videos!! I've watched many over and over. Can you give me an idea where I can get those Silo sockets for the Inductors and capacitors your using? Your Keeping the Electronics Hobby Alive!!

Very informative thanks for posting

August 1962 Popular Electronics "One Arm Theremin"...Beats two RF signals together via two oscillators. One fixed and the other variable via body capacitance. Can/will the circuit in this video help determine the inductor value to make the instrument function, because it's been nearly impossible to locate the two specified JW Miller RF coils?

w2aew, how do you connect a sweep frequency generator 20hz to 20Khz to an inductor to plot the frequency response on a spectrum analyzer or what else can you use to plot the frequency response besides a spectrum analyzer. The Inductor only has 2 wires so if you connect the Lab Sweep Generator across the inductor how do you connect the spectrum analyzer to plot the frequency response of the inductor?

great video wich explain how to measure the coils. I like your ARRL sliding rulers !!!! How to get it? Is there a way to print the ruler in a bunch of paper foils and to assembly them? thanks.

Hi, Excuse my questions, I guess that 0.04 on the schematic is .04 uF. I guess the electrolytic kind of capacitor on schematic are not + or minus except for the 0.04 Tantalum. Did I miss the explanation for the 2.2 uF capacitor? It goes from the ground to the drain of the JFET? The red clamp from the LC meter is grounded or it is not by the square hook? Nice video . JPD

Great video. Thanks

Could you use something else instead of if cans? I am trying to make a superhet receiver and I can't get my hands on any 455khz if can.

Great video. Can you give a list of JFETs to use. I have a few on hand. Thanks

very nice video. how can i build a 455Khz ift ? You hve place a 2.2uF ?

Hey, folks, the BF246A works as well. Just replace the 470R by 1K as well.

Could this help make a coil frequency that the tone resonate at C-528 hz or A-444 hz at all?

Thanks for the great content! Does the parasitic capacitance of the transistors not influence the resonant frequency of the tank circuit? If not how so?

Relay coils and Solenoids coils are considered LCR networks so they are considered reactive loads? If a relay coil or solenoid coil needs 12vdc at 1amp of current to energized turned on. When you set the lab power supply to 12vdc at 1amp since the relay coil or solenoid coil is an reactive load/LCR network its going to need more current because its an inductive capacitive load?

Is it possible to use a spectrum analyzer with a tracking generator to measure impedance vs frequency when a toroid is put over a coax line? I wanted to explore common mode choke performance.

Very helpful circuit indeed...Thank You! Can this circuit be used in reverse? meaning...If you had an earlier vintage known/marked value IF can (with internal capacitors) and these capacitors needed to be replaced, could this rig be used via substitution method to determine the correct capacitance value to obtain resonance?

Hello. Thanks for all of your videos. I have built this circuit and have used it to test several unknown inductors. it is also useful to determine the self resonant frequency of components. I have a question for you about inductors in general. For a given inductance value and all other factors equal, does an air coil inductor have a higher Q factor than a coil wound with a tunable ferrite slug? Also, how does the Q compare between toroids and air core? Is there some advantage for using pi wound (3 sections on a core) in series for larger inductances like 1 mH as opposed to a single winding? Thanks again. I enjoy your videos especially the Back To Basics videos because your demonstrations really help clarify these topics.

Hey Alan, enjoying your channel! Getting seriously back into electronics after an absence of a few years... Trying to find the 2n5245 (obsolete) or the J310 (also obsolete) don't have a sub guide (yet), do you have any idea what I could use instead? Even the trusty MPF102 is gone... Lot of catching up to do. ;) Slowly working my way through your vids.

When using an LCR meter to measure the inductors winding inductance and capacitance. The LCR meters has two different modes In series LCR and in parallel LCR to measure but then you can calculate the resonance frequency, but how would you know at what frequency is the resonance frequency? When winding wire around a magnet what determines the winding inductance and winding capacitance?

k6olg has a similar circuit in winter 1993 of communication quarterly.but uses a big t-80-2 tank coil of 25uh...and said the mpf102,s should work in place of the 2n5245 jfets..and has a computer program for the calculations..I have this in pdf if anyone needs it...Love your video's...

Alan is there a practical frequency limit for the circuit shown ?

I am having trouble replacing a 455khz coil used to align my MW radio...I dont have any drawing or diagram so Im at a lost...my question are the red painted coils (usually) the 455khz coil...thanks..

Just letting people know that The Art of Electronics by Paul Horowitz is now in stock. THUMBS up on you video. THANKS AGAIN

Nice demo walt K2CXP

Can you do a video on your copper clad board and solder islands? I've never seen it before. Do you use this because you are working with high frequencies?

I wonder if this could be used to test the resonant frequency of a loopstick antenna I want to build?

It it normal for an IF transformer to resonate on one frequency for the primary and another, significantly different frequency for the secondary? For example, I have an alleged 455KHz IF can that the primary resonates at 455 but the secondary will not resonate at that frequency. The slug is turned all the way out and it still won't make 455. This is a miss by about 100KHz too low.

Sir how did you just put the component to board without any soldering ?Do you have any video that lead me about this topic ? please

I always thought resonant frequency means maximum and AC wave output when you match the correct capacitor/inductor and frequency?

HI w2aew I like the videos, would this circuit work with crystal ?

Do you purchase your solder islands? I usually just make mine from strips of PCB but yours look much nicer. :)

isnt this just pretty much the same as your other video with this little bnc mounted "fast" pulse generator ? or does it make sense to have both oscilators around for some reason ?

If you don't mind, I have one more question about the solder islands. From my calculations, the capacitance of the islands is minimal using standard FR4, but what I wonder about is impedance? The squares I make are usually around .25"x.25" FR4. From my math the impedance is on the order of 25 ohms. Has anyone tested this? Perhaps the Z only becomes an issue at GHz and beyond. Just curious... As always, thanks for the videos and keep up the good work:)

If you follow the link to the 73 magazine article, you will find there is a listing for a program in basic to do some nice calculations for you. Unfortunately, the listing is unreadable. I tracked the listing down from another, higher resolution source and entered it. It checks out with the test calculations given. Today, basic is an obsolete language and hard to find on Windows. I think better in C anyway, so I translated it. /* Coiltest.bas translated to 'C' */ /* G.L.Peterson - 7/1/2019 */ #include #include double F1; // Freq without capacitor double F2; // Freq with capacitor double PI = 3.141592654; // 2 guesses what this is double LS = 0; // Stray inductance in H, if known // double LS = .0000002; // Est 0.2 uh double CS = 0; // Stray capacitance in F, if known // double CS = .000000000001; // Est 1 pf double CT = 150e-12; // Switchable capacitor = 150 pf double L = 0; // Calculated inductance double C = 0; // Calculated capacitance double CD = 0; // Distributed capacitance double FREQ = 0; // Table frequency double TEMP = 0; // Working storage main() { printf("Coiltest.c -- Derived from M. Covington 1989 - N4TMI "); opinput(); // Get resonant frequencies from operator calc(); // Calculate inductance table(); // Display table of possible usage freq's return 0; } // Get 2 frequencies from operator opinput() { printf("/nF2, frequency with 150 pf Capacitor (Mhz): "; scanf("%lf, &F2); F2 = F2 * 1000000; // Convert Mhz to Hz printf("/nF1, frequency without Capacitor (Mhz, 0 if no oscillations): "; scanf("%lf", &F1); F1 = F1 * 1000000; // Convert Mhz to Hz return; } // Calculate inductance of coil calc() { if (F1 == 0) // Can't calc CD if no self oscillation CD = 0; else { TEMP = F1 / F2; CD = CT / ((TEMP * TEMP) - 1); // Distributed capacitance } TEMP = 2 * PI * F2 * sqrt(CD + CT); // L = (1 / (2 * PI * F2 * sqrt(CD + CT)e2 - LS)); L = 1 / (TEMP * TEMP - LS); L *= 1000000; printf(" Inductance: %4.51f uH ", L); if (CD != 0) { CD = (CD - CS) * 1e12; printf("Distributed Capacitance: %4.51f pF ", CD); } return; } // Print table of usable combinations table() { int I, J; printf(" Resonant Frequencies with this coil: "); printf("C in pF\tFreq in Mhz "); printf("-------\t-------------- "); for(I=0, J=2; I

ive been trying to get me one of those electronic inductance coil calculator. anybody knows where to purchase??

w2aew, when you have two coils that measure 6K DCR and wire them "in series". The formula is 6K + 6K = 12K DRC? when you wire them " in series" with only one coil reversed out of phase the formula is 6K + (-) 6K = 3K DRC?

This video, that test circuit, and an Amidon 1-10MHz shielded IF core, magnet wire, and some small caps should make for home winding a rendition of the 8.8307 MHz Kenwood intermediate frequency transformer. I suppose I could even change the reference crystal value(s), and make (an)other IF(s) to match that (those). There is no law that says a Band Scope adapter cannot run at another frequency, is there? Hamfest/Swap meet season is upon us here in the desert, so, I'll see what Kenwood bits can be had.

Question: What are the component collet sockets used ? Need to get some for this project.

Allan, where do you find such sockets? What are they called, e.g. what would I order from DigiKey? Thank you, sir!

EMF means the "time constant LR" of the inductor? because 1 amp of current going through an inductor will have a time constant so the 1 amp is have slope ramp over time which is from the EMF? and the Counter EMF is current backfeeding backwards at 1 amp?

Great 👍

Hi there, I tried to build this circuit with some J310s I bought from Amazon, but I can't get the circuit to oscillate, even after replacing the 470ohm resistor with a 1kohm one as you suggest in your video. Is maybe the 10k resistor too large? I have tried inductors in the uH range (39uH) as well as in the mH range (1.2mH). Can't get it to oscillate. I have built the circuit on a breadboard as well as on a PCB. Same result. Please advise.

r regarding tubes or valves in my case running on 3 volts i've had a superhet front end working with 3 volts such as an ech81 and russian pencil tubes and acorns.

Why was it necessary to add the 2.2uf electrolytic capacitor which was not on the original schematic?

I love your videos and they are done very well! I have a question, I'm assembling OneTesla Coil and I would like to test the coil that I assembled, but I do not know how to measure it - making sure it is working, before connection it to the rest of the kit. One can't just use a multimeter, I don't think, unless there is a way to do so - I'm all ears! I do have few "toys" like: 100Mgz Oscilloscope and 50Mhz Function Generator, few other meters, including the same LC Meter you have on your desk! (I love it, but one can't buy them anymore!) I do not know much about frequency coils and how to properly measure them, but if I get enough info I can make it to work, I think. I can't find someone in Lincoln, Nebraska that would teach me and most of my friends use Arduino for projects (I also do that) and do not know much about this unfortunately! It seems to me you are the perfect person to ask! Anyone else is welcome to help me also! Thanks again in advance!

Right here goes a question and hopefully you maybe able to help me out. I have a Technics Tuner ST-GT650 and T101 which is the Discriminator coil in the FM IF circuit drifted away from its 0V so I managed to get it back to 0v but broke the ferrite core which was totally my fault but was wondering can you take out the broken ferrite stub screw and replace with a new one. I would change the complete tuning coil if I could find one. Now the markings on the side is B005 S4N3 can you help me out please with what value it is and where I can get one. I can send you the service manual by email no problem.

W2AEW, I see a 2.2uF electrolytic on your board there... Am I missing something because I don't see that in the Schematic and my rudimentary understanding of this circuit gives me little clue as to its purpose! Thanks in advance for any comment. 73 KE4CDR

Great video, clearly presented as ever. Could anybody please point me to a simple oscillator circuit that produces a sine wave within audible frequency. I was delighted to get a Colpitts oscillator working, gave me a nice sine wave but it was coming in at 260MHz.

Is a 0.04 uf capacitor?

where do you get those nifty single sockets??

Thanks

What are those white squares around the solder islands on the board?

The more I look at this circuit the more it looks to me like JFET implementation of Peltz oscillator.

Hello ,very good video as tutorial videos How to measure or tune 10.7mhz FM IF transformer on board, instead of offline measuring , thanks

tnx for share. 73 DE PU2SRZ

Why do inductors or coils operate at a colder temperature when using DC voltage/current compared to using AC voltage/current the temperature is hotter and lifespan is lower? The AC and DC voltage and current are the same amount but the temperature of the inductor or coil is a major difference

make a video using nanovna to do this.

Thank you for great videos. I have problem to get the oscillator working. I have tried several ways but no. Was able to get the circuit work with a cristal 7MHz insted of C2 and 680k to ground. Is there other who has same problem as me. 73 de SM5LTG / Ulf

I looked at the archived article and I saw it was blurry and unreadable. You can download the .PDF of the whole 73 magazine (and many others) on americanradiohistory.com.