#199
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- เผยแพร่เมื่อ 4 เม.ย. 2015
- This video shows a simple circuit that was shared by N4TMI in 73 magazine (no defunct, and archives freely available online). It shows a simple 2-transistor oscillator that can be used to test the resonant frequency of an unknown coil / inductor when paired with a known capacitor, as well as the resonant frequency of parallel tuned circuits like IF transformers. This is especially handy for folks that work on old radios and need to identify IF transformers, or want to figure out what value of capacitance to use to resonate with an inductor at a chosen frequency. I show a very handy "slide calculator" that can be used to quickly calculate LC resonant circuit values and frequencies. I made a small modification to the values in the circuit because I used a different N-channel JFET than was used in the article. Here is a link to the original article in 73 magazine from September 1990:
archive.org/stream/73-magazine...
And, here is a link to where you can find the handy L/C/F slide calculator:
www.arrl.org/shop/L-C-F-and-Si... - วิทยาศาสตร์และเทคโนโลยี
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.
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.
After searching for an accurate home-brew inductance measurement circuit, I built the circuit you described back in 2015 on TH-cam. 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.
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.
Really well explained. As a radio ham with no electronic training, this was easy for me to follow and useful. Thanks.
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...
paxmowa Well, I hope #200 won't disappoint! I had an idea in mind, but found that I don't have the parts I thought I did to do it. So, I'm going to have to think of a "plan B" video...
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
As ever Alan, you deliver great tutorials!
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
Another excellent lesson Alan, thanks.
Thank you so much. It's much easier to watch at the direct experience of an expert as you.
Nice little test circuit. Good video.
Love it. Keep them coming.
Nicely done. I've been trying to get the time to watch this since I received the notice of a new video.
I built mine this morning, happy to report it sings happily at 9v, really pleased with it. cheers Alan.
Paul m0bsw
Excellent!
W2AEW de WU2D - great stuff Mr. Nomograph!
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.
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.
As always, well done!
Again a great tutorial !
wow, thx for the info and links! very cool.
New to this, this is an awesome tool!
Now the IBM Deep Blue just crying on the calculation speed of Your rulercalc :))))THX! Good video again!
Realy great just what i was looking for Thanks
Enjoyed, and it got me thinking. 73s de VK6BIL
well done, good audio and video..
Very informative thanks for posting
Very interesting... will refer to this when teaching radio class for acquiring amateur license.
Great video. Thanks
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.
*****i I build it with two 2N3819. I tried to test a brand new 100uH coil. I have about 2.4 MtHzw . Whith wich cap does the oscillator works , 33, 150 pF ? Or the addition of 1/33+1/150+1/150?
Do you have any good sources on the tektronix mdo 3104? (USED)Sam
Unfortunately no, I don't have a good source for used equipment.
I know a few places that sell used test gear, but their prices are not what I consider fair let alone good. MHz Electronics sells on eBay now. Them, and another local seller have absurd prices listed, but usually if I hang around for an hour or two then haggle the price comes down. You can't do that with eBay at all, and MHz has amassed so much stuff the fire marshal took away MHz's certificate of occupancy, so no more retail sales from their warehouse. He has stuff stacked up way above the sprinkler heads, so the fire department finally made him close to the public. I hear of people talking their way in, one at a time. I only see the guy at auctions now. He pays way too much for stuff to begin with, and he is addicted to bringing home junk by the semi truck load. Who wants 18 1960s hard drives the size of dining tables? Aside from MHz, of course.
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.
Something about coils and frequencies.... sorry I was transfixed by that glorious MDO3104 on your bench :-) Great video, as usual, Alan.
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?
very nice video.
how can i build a 455Khz ift ?
You hve place a 2.2uF ?
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!!
The sockets are made by Mill Max - I purchased them from Mouser.com.
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!
You can use this circuit to check the suspect transformer's winding inductance, or even the ring technique in this video:
th-cam.com/video/74fz9iwZ_sM/w-d-xo.html
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...
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?
Nice demo walt K2CXP
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
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?
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 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.
There is a link in the video notes where the slide ruler/calculator can be purchased fron the ARRL.
Could this help make a coil frequency that the tone resonate at C-528 hz or A-444 hz at all?
Great video. Can you give a list of JFETs to use. I have a few on hand. Thanks
Just about any general purpose jfet intended for small signal / oscillator use should work. You might need to adjust the source resistor as I described.
Great 👍
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?
It can certainly be used to get you close! Parasitic capacitance of the circuit will alter things a little, but you should be able to get close enough to dial them in.
***** Thank you for the reply!
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?
Yes, it certainly can - more so at higher frequencies, not so much as lower frequencies.
Are there different choices then for FETs with lower parasitic capacitances that can reduce this effect or is it possible to add resistors to swamp the parasitic effects in some way? Was the choke in the original design significant?
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.
The J310 is still available from Mouser and Digikey.
@@w2aew Thanks Alan!
Hope to chat with you on the air sometime!
@@number6of1 I found the J310 jFET on eBay - a set of 10 for $8.68 including shipping. They work great. (See my reply to the video dated 10/8/19).
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.
Good questions. I think in general that air-core have higher Q because there are no core losses. Of course, for very large value inductors, there would be a lot of turns, thus increasing the wire resistance which lowers Q. Toroid and straight core inductors should be similar in terms of Q for similar core material and inductance. I really am not sure about pi wound advantages, so I can't offer any insight.
+w2aew Thanks.
Do You have an good source on an used tektronix mdo 3104?Sam
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?
Phillip S Phillip check out Alan's video #122: Electronic Circuit Construction Techniques
Thanks Bob Marston
Hey, folks, the BF246A works as well. Just replace the 470R by 1K as well.
any other component values stay the same? thanks!
HI w2aew I like the videos, would this circuit work with crystal ?
No. But I do have a video showing how to build a simple crystal test oscillator:
th-cam.com/video/blalAktxFoI/w-d-xo.html
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
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.
mike94560 Not easily. To test a common-mode choke, you need to test with a common mode signal. Sending a signal down the coax the "normal" way with a SA+TG is not a common mode signal.
ive been trying to get me one of those electronic inductance coil calculator. anybody knows where to purchase??
I wonder if this could be used to test the resonant frequency of a loopstick antenna I want to build?
+Patrick Briggs No, probably not. a tuned IF transformer looks like a high impedance at resonance, while a loop antenna looks like a low impedance at resonance. Better off using one of my vids showing how to tune an antenna or measure complex impedance with a simple bridge and scope. Other videos like the ones on directional couplers might also provide some good ideas.
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?
Just letting people know that The Art of Electronics by Paul Horowitz is now in stock. THUMBS up on you video. THANKS AGAIN
Yep, my copy is on order!
ElectronicWizzard
Fed Ex should be delivering mine today!
ElectronicWizzard I have a 1st edition, bought years ago at 1/2 Price Books for 3 bucks, I think. It is a great reference, and not bad reading. I wonder if the updates will be worth the(gulp), price tag?!?
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.
Do you purchase your solder islands? I usually just make mine from strips of PCB but yours look much nicer. :)
I"ve done both. For the times I purchase them, I use qrpme.com
MeSquares, Perfect. Thanks
Alan is there a practical frequency limit for the circuit shown ?
Bob Marston Yes, I'm certain there is. I found that it worked from below 200kHz to above30MHz. For high-Q devices, it will likely work higher than that. With some component changes, it would work into VHF.
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.
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?
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 ?
The application using the fast edge circuit wouldn't be useful to determine the resonant frequency of IF transformers.
I think there is a way that the application using the fast edge circuit could be used to measure the resonant frequency of IF transformers and even measure transformer inductance and parallel capacitance.
Let us assume that we have an LC circuit with unknown Lx and Cx connected to the fast edge circuit. We will use two measurements 1) only oscilloscope probe with known capacitance Cp is connected and 2) we add additional capacitor in parallel to the probe with known capacitance C2. In these two cases resonant frequencies will be f1 = 1/(2*pi*sqrt(Lx*(Cx+Cp)) and f2 = 1/(2*pi*sqrt(Lx*(Cx+Cp+C2)). We can solve these two equations to obtain Cx and Lx. The result is Cx = f2^2*C2/(f1^2-f2^2) - Cp and Lx = 1/((2*pi*f1)^2*(Cx+Cp)). Finally the resonant frequency is fx = 1/(2*pi*sqrt(Lx*Cx)).
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..
I don’t think there is a standard color. I’ve seen 455 cans with red, yellow, black and more.
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:)
I've measured my homemade lands and they're typically about 1pF. The MePads are about 1.6-1.7pF due to thinner substrate. Even the MePads present about 100ohms capacitive reactance at 1GHz.
Thanks
Question: What are the component collet sockets used ? Need to get some for this project.
They are called Pin Receptacles, made by Mill-Max. They have dozens and dozens of varieties.
@@w2aew Wow ! Gazillions of them. Could you clue me in on which ones I need ? Never seen these before.
@@jameshall5835 Here's an example of one of the ones I use: 0314-0-15-01-34-01-100
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
The components for the test oscillator *are* soldered to the board - I just didn't show the construction part of it. I soldered pin-sockets for the leads of the parts being tested. I did a video on breadboard construction techniques, which can be found here:
th-cam.com/video/kH110yjYZ2g/w-d-xo.html
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!
If it is a simple (albeit large) coil - you can measure its resistance easily (to confirm continuity), and you can measure its inductance. Do you know that the expected inductance value is supposed to be. You may be able to measure this with the LCR meter, or you can measure using a series L-R circuit with your function generator (square wave) and scope.
Thank you for quick reply! I do have a scope and function generator, but I never done this. I was looking here and other places, but I could not find step by step that would help me to figure this out. I'm not the brightest light bulb under the sky in this case - sorry. Bu if you give me few pointers, I'll try to do it, but I do not have any experience with coils at all. I learn the best with guidance and or video/person/hands on .
I used the LCR meter, like you have in the video, to your write hand... I measured 45 mHy, ; I had to relearn how to re-calibrate it, since I don't use it very often. But I don't know what I should set up in my Frequency Generator when connecting it to my Oscilloscope. I think the probe from the Oscilloscope isn't connected directly, I think.... during the test (this is based on the oneTesla instruction, that is incomplete to me: onetesla.com/tutorials/tesla-coil-tuning ) but I never done this before, so I have 0 experience doing this. When I was looking on this place and on the Internet, I didn't find details how to do this. I assume the distance from the coil would also need to be somewhat close, but I don't even know how close. How many volts and Peek-to-Peek should I send into the coil and what about all the other criteria that I can set in the FG? Sorry, I just don't know anything about that kind of setup and how and where to connect the leads. I wish there is a video for simple guy like me! My direct email is: czecht@gmail.com and I also have Skype under the same name and email. I'm here until late evening hours most days, but also during the day I try to play with all my hobbies here....Thanks again for your help! (Sorry I do not know your name)
Allan, where do you find such sockets? What are they called, e.g. what would I order from DigiKey? Thank you, sir!
I use pin sockets from Mill-Max. Similar to these:
www.mouser.com/ProductDetail/Mill-Max/0552-2-15-01-21-27-10-0?qs=sGAEpiMZZMs%2fSh%2fkjph1trRw3Iqu89Lv9TGKSdMTRvY%3d
Not sure the exact part number I've used in this video, but the above link shows a good example.
w2aew Thank you, sir! Just what I needed ;)
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.
Have you measured the drain voltage on Q2 to make sure it is in the saturation region?
@@w2aew Finally got this to work. I had to increase the 30pF capacitor on the input to 1nF. Probably because my resonance frequency was pretty low (like 25kHz). I actually ran a LTSpice simulation of the circuit to see why it was not working and found this out that way.
I can’t get my circuit to oscillate. The Q2 drain voltage is 11.5 V with an 18.5 V input. Any ideas would be appreciated!
I always thought resonant frequency means maximum and AC wave output when you match the correct capacitor/inductor and frequency?
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?
The DC Resistance is unchanged - it doesn't matter if it's reversed or not.
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.
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?
No, EMF is the Electromotive Force, which is essentially the voltage. See en.wikipedia.org/wiki/Electromotive_force
@@w2aew If the voltage is +12vdc the EMF is 12? That doesn't make sense that the EMF is the same as voltage because C-EMF is following the opposite direction. The impedance of an inductor/coil is based on the EMF value?
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.
You certainly can get a Colpitts oscillator to run at audio frequencies by adjusting the L and C components appropriately. Another simple oscillator (if you don't mind a little distortion) is a simple phase shift oscillator as shown at about 7:22 in this video:
th-cam.com/video/81C4IfONt3o/w-d-xo.html
Thanks very much. I did try larger values of L and C but it looks like I need to persevere down that route. I've just checked my notes and the frequency I quoted above should read KHz not MHz. I'll certainly look into the phase shift oscillator. Thanks again for the response and for all your excellent work.
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.
If the part number for the coil isn't listed in the service manual, then it may be hard to find a replacement other than from a similar unit. You may be able to replace the core from a coil from another tuner - they should all be similar enough if used in the same IF frequency.
@@w2aew I have the service manual and the part listed is RL14B005-Z and just states Coil but the marking on the side is B005 S4N3 could you recommend what I could use as the ferrite screw is broke but sort of still functioning as a discriminator.
@@johnny1408 RL14 is likely the manufacturer's model number for the series, and B005 is the specific part in the series. I'm sorry, but I don't recognize this manufacturer's code, so I really can't help. It is possible that a core from another inductor from a different tuner/receiver may work, nothing to lose to try it.
Is a 0.04 uf capacitor?
tnx for share.
73 DE PU2SRZ
where do you get those nifty single sockets??
They are called "pin receptacles", made by a company called Mill Max. Available through distributers like Digikey, Mouser, etc. Lots of different sizes available.
@@w2aew Awesome! I went ahead and made these with two J113s. Other than mixing up the pins (On Semi and Fairchild versions have different layouts!) things went smoothly. I also used 1k for the long tail. Worked as described. Your videos are really helping with my adventures into RF circuits! 73 de VA3GPJ
What are those white squares around the solder islands on the board?
It's just a bit of white silk screened ink that is included on the little solder pads offered by QRPme.com.
Why was it necessary to add the 2.2uf electrolytic capacitor which was not on the original schematic?
Always a good idea to add some bulk power supply decoupling.
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
That is just a power supply filter cap, sitting between VCC and GND.
@@w2aew Ahh. Got it. Thanks.
Hello ,very good video as tutorial videos
How to measure or tune 10.7mhz FM IF transformer on board, instead of offline measuring , thanks
The more I look at this circuit the more it looks to me like JFET implementation of Peltz oscillator.
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.