Thanks I have been trying to completely understand coils in AM circuits an this is the first video that demonstrates what happens (and I have watched alot of videos). Now I can do my own experiments.
Many thanks for making this video. You teach the WHY as well as the HOW and I learned from this better than any other on the subject. Again, thank you.
Very interesting info. I'm considering a MAG loop antenna for amateur radio and I have a lot to learn about loops, so thank you very much for this information.
You do a good job of organizing, explaining, demonstrating the subject.......you present in a logical, sensible mental sequence. I like the way you think and you're worth listening to......no condescension intended...... Greetings from Central Texas.....Rgds, fm
WOW! every once in a while someone explains something so you get it!!! Thank you so much. I was thinking just as you stated part way through... "but a coil on it's own doesn't resonate without some Cap."... bingo now I get it!
Great video, once you know the relationship between capacitance, reactive capacitance and how impedance is calculated. Based on the definition of impedance, it is easy to visualize how resisting AC would lower the resonant frequency of a loop. *A loop has to be higher frequency, so the capacitance pulls it down to a lower frequency. “... I need to understand the relationship, and get a visualization as to why. I think I could visualize how impedance and the speed of emf through a metal (which is lower than the speed of slight through air) would mean that we would need shorter lengths than that we might calculate per frequency otherwise... But I don't understand why capacitance tunes a loop, whether turns, or a capacitor, or a natural capacitor gap between the leads coming into the coil. It is interesting that the variable capacitor is put in the loop in parallel with the loop and hookup and is able to bring up or down the resonant frequency. So taking turns off, lowers the capacitance which raises the resonance of the loop. (what is puzzles me is that the circumference changes with less turns). Adding a ferrite core dramatically dropped the lower frequency. (I need to imagine why this is true. Possibly increasing the capacitance, however, I still only can visualize an impedance to frequency relationship. And am missing a mental visual puzzle piece as to why capacitance affects the frequency so much. If capacitance effects impedance, capacitive reactance.... Reactance is both inductive reactance and capacitive reactance....Impedance, denoted as ( Z ), in electrical circuits is calculated using the formula ( Z = R + jX ), where ( R ) is the resistance, ( j ) is the imaginary unit, and ( X ) is the reactance... So, changing the capacitance indirectly changes the impedance, which obviously effects the resonant frequency of a loop, because the definition of impedance is the resistance to alternating current. And I can visualize resistance lowering the resonant frequency. Important for calculation (remember that stands for Capcitance and is broken down to X_C and X_L: For capacitance, the capacitive reactance ( X_C ) is calculated using the formula ( X_C = \frac{1}{2\pi fC} ), where ( f ) is the frequency of the signal and ( C ) is the capacitance. I don't yet understand this, “As the frequency increases, the capacitive reactance decreases, meaning that capacitors tend to pass higher frequencies more easily and block lower frequencies. Therefore, capacitance affects the total impedance by contributing to the overall reactance in the circuit, particularly influencing how the circuit behaves at different frequencies.* although, I understand, “capacitance affects the total impedance by contributing to the overall reactance in the circuit, “ in light that capacitant reactivity capacitance is part of the reactance calculation, which affects impedance. Tightly bound means more capacitance. Obviously, additive, so more wire coils means more capacitance which raises impedance, which resists the ac, which lowers the resonant frequency. (if I am not confused or typing wrong.) It is important to remember that the resonate frequency is the highest frequency that the loop can receive. I don't understand this, really. And it doesn't make any sense that people talk of targeting the middle of the band rather than the highest part of the band.
not having an oscilloscope and RF generator, I'm going wing it and play with a coil to help improve reception on a mid range AM station. Thanks for the info. I picked up a lot.
Thank you. Very practical way to learn and understand how resonant frequency of antenna works. Understood more about loop antennas from this than I learnt watching and listening to 50 other videos.
The big (missing) question is how many turns do you wind to be near a specific frequency? What is the effect of having a lot of space inside a loop or coil? Give us some formulas?
How would you use a nanovna-h4 to determine the self resonance frequency of a magloop without the tuning capacitor connected. This is an Octagon 3/4" copper pipe with 24" sides and about a 4 - 6" opening in the loop where a trombone capacitor will be connected.
Utterly GREAT video but It would have helped a bit if you had told them that the Signal Generator was THE crucial piece of gear. The scope is a great luxury but it is only playing the role of detector. Much less expensive ways are feasible. A diode circuit into a multimeter would show peaks ..a sort of Xtal set. AND some modern cheap digital meters might even respond to the signal on AC volts at such low frequencies without an external diode circuit. We are not looking to measure the signals here. We just need to display their presence and show when they get bigger or smaller. Of course, get a scope IF you can. You'll really add to your test gear, but don't despair if you can't, just yet. There's always more than one way of skinning a rabbit. GET a SIGNAL GENERATOR. the best you can afford. It's your next priority. But all is NOT lost without one! Good trick..... IMPORTANT alternative.. without a sig gen. nor a scope. If you can listen on this LF freq. and you must be able to listen or you wouldn't be building this antenna in the first place(!) , put your tuned loop in series with the rx antenna input socket and a random chunk of wire..It'll pick up SOMETHING however badly. Sweep your loop tuning capacitor about .You'll hear a deep notch in lousy noises when you hit resonance. Can't find it? Go off looking for it.. The sig gen. / scope is the luxury method but there's always more than one way of skinning a .....
I agree with above comment. Video was very straightforward and illustrated resonance very well, but acquiring the test equipment you used for $50 is very unlikely. Even at the local Hamfest here in the South of England, I've never seen such a bargain. You can obtain a function generator for up to around 24MHz fairly cheaply, but the only scopes for less than $50 would probably be too insensitive and cover little more than audio frequencies. As most people who view your channel can build simple circuits, I suggest using a Franklin Oscillator circuit, coupled to a cheap Chinese frequency counter module. There are several circuits on line, using 2 devices of the common types of FET and using common BJT transistors to buffer the output to the counter module. As there are two active devices in the oscillator and plenty of gain, only a light coupling and two-terminal connection to the inductor or tuned circuit is required. Since your video was made, your fellow RU-vidr, MIKROWAVE1 has produced a Franklin circuit and there is an excellent little Simple RF Generator Circuit by ZL2PD. Although I've found that an LCR meter gives fairly good results with loops like the 8-inch ones you used, I obtained very misleading results when winding a spiral loop, due to self-capacitance effects and wound twice as many turns as needed.
I noticed Tesla has this massive spiral coil he used for high-frequency experiments (pre-dating Tesla coil). In the photo, it looks like the radius is 4 ft, around 100 turns, inner radius is about 4 inches. This might work out to around 15mH, similar to the 15mH coil you used for 60Khz. Would there be an advantage to having an air-coil for 60Khz reception? Basketweave to have high Q? 60Khz was high frequency for his day.
Hi Paul, Love the videos. I'm interested in purchasing a pair of your 60 kHz antennas for a WWVB project I'm working on. Are they available for sale? Keep the videos coming! 73 Tyler N1QQ
I've been watching...! This is also a good method for tuning IF cans that someone else has screw-drivered... As in mess up the tuning... It will allow you to bring the IF transformer back to it's 455kc spec...
I found it very informative and at the moment the only question i have is what the heck is Moxie?, I never heard of that drink. I recently got into scanning the air waves using a SDR and even built 1 antenna to capture the NOAA sat passes. and now I've been checking out the SW bands, have been amazed at how many signals there are out there and from how far away I'm getting them, but some of the bands are very quite and I suspect its my receive antenna not doing a good job at the lower frequency's.
As always great job on the video . I have been wanting to build antennas fo MW - and lower also the 160m and 80m but thought I would need a ton of wire and an acre of land or more. Now you have given us the answer with ferrite antennas. Also coupling it to possibly a youloop or other loop to feed into my Sdrplay RSP-DX low band A port HDR port. My thoughts are it should be amazing. My goal is to build an all band monitoring system that actually works. I'm a medically retired USMC vet and this is all I basically do now. Thanks again AA4CP Chuck Patterson Port Salerno FL USA
Hi Chuck, Thanks very much for your service, I'm also interested in medium wave dxing and have splashed out on a new RSP-DX, I'm expecting great things from it, I've got a Wellbrook loop but I'm also interested in that you loop as I have just seen an interesting article on it somewhere, something about mobious loops and mysterious things along those lines. regards, Gary GW7TED
Дружище привет из Сибири, я не ветеран войн, но служил в 77-79гг в Арктике, в радиотехвойсках и знаком с прохождениями радио волн, плохо что незнаю englishc, обучался в школе немецкому языку. Но, думаю ферритовые стержни прекрасны на приём, ни коем случае на передачу. Вот как это оформить на НЧ-диапазонах, на передачу-это уже большой вопрос, может подскажете, буду благодарен особо. SK73!!! op. Haris, 3000kgc
I think this was an extremely informative tutorial/demonstration of how to measure the resonance of a coil that many amatuers would definetly benifit from . Thank you for taking the time to make this video so that others may benefit from your knowledge.
Am I missing something here .... according to my understanding of coils .. they do NOT have any resonant frequency.... unless they are coupled to a capacitor to form a resonant tank circuit
Watch @9:21 You will get the answer.... All inductors have some capacitance, so it is resonating. You generally bring down the resonance frequency by using a variable capacitor with is coil to a desired frequency.
@@rrangana11 ok ... I see what you mean here... all coils do have interwinding capacitance ... but I assumed in the case of a medium wave antenna coil, this capacitance would be well short of forming any resonance with the coil ...
Now i have to repair my old scope that has sat for probably 20 years. I think i knew this but had forgotten my basics. Thank you for a nice video and great ideas. I am building a couple of loops now for HF and 6 meters. Tom N5UEB
I like this video. You got directly to the information that I was hopping to get from this video. Simple explanations but they where correct and simple to understand. I could see the effects on the oscilloscope of what you where saying. Thank you very much. I hope you get more viewers. Keep up the good work. We need youtubers like you.
Hi Ron, Thank you. I will be doing an open frame loop video soon. roughly 3 feet on a side. This is the platform on which I built some of my first loops. I will build it, then test to see where it resonates. Using a general coverage RX It is easy to then "tune: the loop to your area of interest. Stay tuned.... Please subscribe if you have not already.. and thank you for the kind words
Thank you for the wonderful video!! Could you give the values of capacitances you used and/or the range of the variable capacitor? We are making one for SID Monitoring
What would happen if you made a series vs. parallel LC circuit for these passive receiving antennas? I know that for the WWVB-spoofing antenna I built, I used a series LC circuit since the transmit antenna is powered by an ESP32 GPIO output and by using a series circuit, I could assure that the reactance was minimum at the resonant frequency so there would be little chance of drawing too much current on power-up or power-down since the reactance out of resonance would be higher. But for a passive receiving antenna where one is not pumping current into the antenna, does it make a difference whether parallel or series?
Nice demonstration Paul ! I have a 20cm/10mm ferrite bar, and I need to use it for VLF (20-150kHz). from your experience is better to put on it multiple layers (to say 3000 winds on 3 layers for example ) for a better Q factor or just one layer ? On the other hand, coupling coil to receiver, ie better to be over the layers or separate in a side of ferrite ? I wait your advice - my best 73 and thank you in advance !
That's a really instructive video. Thanks. What's the smallest diameter and how many subsequent turns would you advise that would work for direct connection to a sound card for a SIDD detector? I only have a balcony, so space is very limited.
All I need is an oscilloscope and an RF generator? Oh, and clip leads. Well...I have none of those things. But I'm going to watch this again once I do.
thats the whole point here, a coil has no resonance on its own, so the measurement is worthless , not telling enything, the inner capacitance of the scope mostly 20pF depending of the quality is making the coil act as a resonant circuit
Awesome video. I wasn't even looking for this info, it just looked interesting. It really makes me miss my scope which my current house is too small for! Super informative, and really well conveyed - you're a great teacher. Thank you.
To test loop antennas using a function generator and a signal analyzer, can I just connected the function generator to the antenna and the signal analyzer probe to the antenna to analyze the received signals? Can this method be used for testing loop antennas?
You made it big enough loop frame and wrapped it and and crazy cool foot sick and foot tall round the frame the frame is actually 6 ft tall could you turn that up with it machine to create a doorway and sit the other one up with twin somewhere else and instead of passing the street in the doorway so the energy door will open up create a link to one another miles and miles and miles apart with a door you see is the other side of the tunnel that's not a tunnel exactly energy films that's connected to the other energy things you know they're separate within that energy family where you walk from one building to another through the door once you get the doors soon the link to one another and open a energy door that will transport you to the other door you walk out of it like walk through the doorway of the clean room but you're not in another building some distance away from the other building and the other door would this work or just great imagination work that way what if you could find a way to open the doorway into other dimensions with travel to another dimension through a coolld door
How to build one that I can connect with a coax cable so I can place the loop in the attic and turn the antenna and variable capacitor with a stepper motor?
Thank you very much. I understood the concept of adding and subtracting turns to get resonance but your neat demonstration of self resonance (combined self capacitance and inductance) being the highest frequency that the coil can be used for was just brilliant and gave me some satisfying aha moments. I have made these for over 50 years and still get a kick out of them. I use remote tuning with varicaps so that the antenna can be in a relatively noise free environment. Spare old test gear is much more expensive in Australia.
Excelente, sólo faltó un diagrama/dibujo para construirla. 😉 Slds TKS desde Argentina 🇦🇷👋 PDT: Ya mismo procedo a buscar en su próximo video que trata de la misma temática 👍
How would you recommend making an omni directional VLF antenna? Would you use 3 different antenna's in series but offset by plane? Or 2 that are offset on the x/y axis and exclude the vertical axis? I want to listen to anything between 1kHz to 30kHz :) Surprisingly, there isn't a whole lot on the amateur side of VLF for building antennas
Kevin.. that is a very interesting question. The self capacitance is distributed throughout the coil, between turns. So.... I guess what we have is a bunch of little inductors( each turn) in parallel with small amounts of capacitance(space between turns) and the whole mess is in series to give one larger inductance and associated capacitance. One way to change that fixed capacitance between turns is to space the turns out a little, farther apart, less C and less L as well. In some of my loop designs, I actually has 2 windings and a switch to put them in parallel, and then in series, dramatically increasing the frequency coverage. W1VLF
a coil cant be resonant without a capacitance, this is useless, it resonates withe the capacitance of the scope , what you measure is in fact the error of the scope and says nothing about the coil,
No that is not correct The resonant frequency is set primarily set by the inductance (number of turns) and the interturn capacitance which is in parallel with the inductor. 2 parallel conductors exhibit both inductance and capacitance. W1VLF
I've done this when I was still working in electronics and had access to my bench. I would put some resistive isolation between the generator and loop.
Overall, building your own loop antenna, Resonant is yours "Ideal" working antenna frequency? Great video. Thanks for sharing with us. You said yours equipment is worth 50$, sadly at my location the cheapest oscilloscope and signal generator starting from 200$.
excellent video. I was going to start building a crystal radio but every video has different info on winding coils. This will help me refine my coil to resonate at the top of the MW band and be able to tune across the whole band with the variable cap. It will also be easier to find resonance for coils on HF bands. Thanks
not quite sure who this video and the explanations would be good for - except for experts - but then again, why would experts watch *this*... bottom line: the (logic of the/thought train) explanations are hard to follow for your audience, the beginners
@@bradleyleben7785 Hey Brad... I think you right the first time !!! LOL... I understood what you meant when and figured the spell corrector to be at fault... Still I think "Looniest" applies!! LOL
Hi Great video, I was looking for something to use my new Nano Vna-F on and found this video thinking it would give me some ideas about the nano then I discovered my old function generator that's been kicking around for years and by strapping it to my scope I was able to quickly find the resonant and usable freqs of a couple of loops I had made years ago and then forget about because it was like working in the dark, do I go up in freq do I go down? shall I add more loops? should I add or remove more capacitance, it makes it all a lot easier to understand when you can actually see the effect of your adjustments so thanks for this, also I wish my shack was as tidy as yours ha ha thanks again. Gary GW7TED
