Finding Loop antenna resonant frequency

This video describes a simple way for the average radio experimenter to determine the resonant frequency of a loop they are building. Using just an oscilloscope and an RF generator. Simple process is described. Not a DIY antenna build but more of the theory behind what is going on so an intelligent design can be built.

[@vivekyadav]

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.

[@W1VLF]

Hi Vivek.. Thanks for taking the time to comment. I am glad you found this helpful.

[@philticehurst2401]

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.

[@W1VLF]

Hello Phil, Thank you for the kind words .. Great Fun !! Thank you to my friend in Australia

[@bradcdavis00]

I understand the concept of resonant antennas much better after watching your video. Thanks for taking the time to make it.

[@W1VLF]

Well Thank you. I appreciate it. Its make it worth while to make videos and know some folks found it useful

[@THEALBRL]

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.

[@ronbercan1000]

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.

[@W1VLF]

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

[@highwayrider66]

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.

[@davidpassey4771]

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.

[@consciousness1237]

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

[@GaryRowlands]

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

[@user-rd8tc9wz6v]

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

[@qchatgreg]

quick note .. thanks for the video, it gave me inspiration and methodology to make a loop antenna for 2.201MHz .. specific application .. for recieving a marine weather fcast (aust) on a boat using a small handheld HF rxr. got loop resonating at around 2300, and with a fixed 100pF cap, its almost spot on .. waiting now for air variable cap to arrive . enjoy your vids, informative style. thx

[@johnwilson4909]

W1VLF - I like your videos. The no nonsense approach and straight talk are great.

[@W1VLF]

Hello John, Thank you for the kind words. Its how I am, in real life. Not a fancy person by any stretch.

[@seanmangan2769]

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.

[@jimnantz2265]

I've seen those other videos. They tell how to make the antenna but they don't tell how to figure out what frequency it resonates at. Thanks to you, I know how to figure it out. Thanks a lot.

[@LJacyHenry]

I went to tech school studying electronics, studied books and watched videos with guys and whiteboards doing math. Thabks for actually showing me how these things work. I would love to see a simple guide to using marconi antennas in low frequencies. Thanks for the video.

[@OIE82]

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.

[@hokepoke3540]

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

[@manoharandass8674]

Simple and clear explaination. Loved it I learned a whole lot. Thank you.

[@W1VLF]

I thank you sir for watching

[@fredmetcalf]

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

[@W1VLF]

Thank you Fred.. No condescension taken. LOL Greetings from Connecticut

[@hmaghera7746]

Cant get over how easy and useful this trick is. Absolutely bonkers. 👍👍👍👍

[@superrodder2002]

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

[@DM-fz3ly]

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!

[@consciousness1237]

I thought the same thing but now I see how I failed years ago , he is truly a great instructor

[@ramblinred1]

Enjoyed the video! Learned a few things too. I now have a better understanding of capacitance and number of turns to frequency. Thank You! Very easy to understand.

[@W1VLF]

Thank you for the kind words.. W1VLF..

[@buddyhoover57]

I have been interested in building a broadcast band loop antenna for a couple of months, but have been unsure of how to determine the number of coil loops. Your video answered my questions. Thank you, thank you!

[@W1VLF]

Hi Buddy, Thank you ... I always encourage experimenting. W1VLF !! Go for it!

[@ralph72462]

Hey great video I am watching and very helpful simple hints for tuning antennas and testing their resonant frequencies without too much complication. I found it very helpful and practical. Thank you for sharing.

[@radioastronomy2001]

Very good video. Probably one of the best I have seen on this topic. You could actually make one more showing how to tune the loop using just ears and noise. Perhaps some easy to make generator. Not everyone has access to the equipment even for $25 dollars a piece. Also, some people may not know how to use this kind of stuff. Thank you!

[@civicbynature]

thank you for this video! I learned a ton! I finally understand why and how tuning is done and what a variable capacitor knob does to an antenna and why it is used in radios. Mind Blown!

[@dennisk5818]

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.

[@fjs1111]

Paul you have some great videos on RF -- thank you!

[@vrjb100]

Great video. Theoretical I know how it should work. Having it demonstrated is great. Practice vs ideal theory....

[@W1VLF]

Thank you !! W1VLF

[@spraynprey1044]

hi, just found your channel, you asked for comments so here is my input. Yes, we are watching, and we have loads of questions, or at least I do. For instance, what is the range of your adjustable capacitor? where can these be found? also, when you are making a video, for beginners such as myself, and you are using multiple pieces of equipment/parts, it greatly helps us if you include everything in the screen frame. no matter, how big or small its size or purpose, we like being able to see it. even if you explain what is just out of view or how insignificant it is, most of us still want that visualization. thanks, have a great day and keep making educational content for all of us enthusiast out here trying to learn.

[@ColeDedhand]

Coils will also resonate when pumped with a harmonic so be careful that you don't fool yourself about the resonant frequency.

[@LadiboiJoy]

Will they resonate with earths natural fre harmonics.?would gravity shadow occur..like a. R.f. shadow? Creating weightlessness anti gravity?

[@khancious7720]

Thank you for these in depth videos. Valuable source of information

[@W1VLF]

Glad you like them! Thank you W1VLF

[@steveratzlaff]

Enjoyed the video, have seen your stuff for sale for years, nice to see you in person. Steve AA7U

[@W1VLF]

Hi Steve Thank you for watching. I apprecite your comment

[@TerryLawrence001]

Very good vid. Inspired me to get back into antenna making. Thanks!!

[@W1VLF]

Glad to hear it Terry.... Its easy and its fun and a great learning experience... W1VLF

[@189625]

I have a whole bunch of loops that I've made over the years. Now I have a way to figurate out why they don't work. Thankx!!

[@W1VLF]

Hi Robert.. Thanks for taking the time to comment. I am glad this helped

[@availablenowonwards]

Can't be simpler than this.. really great job..!!

[@davesradiorepairs6344]

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...

[@weslewis8748]

Great video, Paul...thank you. What formula can I use to calculate resonant freq. Based on wire diameter, loop diameter, etc?

[@luismirandakunert3475]

Nice, very interesting video. Optimun method because for lower frequencies.than 50KHz it is impossible to measure the resonance frq with a Vector Network Analyzer or utilizing a Tracking generator with a RF bridge. That usually work upper to 100 KHz Learning new things today Thanks!!

[@kirknelson156]

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.

[@bobpotter895]

Very straight forward information that I will be able to use. Thanks

[@unklewink]

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.

[@arome83]

I enjoyed your video but more importantly, I'm learning. Thank you! By the way... I'm interested in building a very low frequency antenna. Any ideas?

[@dennisgarber]

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.

[@K6TJO]

Great video to help me better understand antennas. Where can I buy such inexpensive used equipment? So far have not seen such at those prices

[@jogiemka]

Great information, well presented! Keep up the videos. 73!!

[@de_w8tam]

Hey Paul, you inspired me to make an antenna. That's not exactly the absolute peak of performance, pretty much any time I see an antenna I want to make a copy of it. :D I am thinking about getting on the 472khz band, and a tuned receiving loop seems like a decent place to start. I built one of those PA0RDT mini-whip antennas, but it didn't blow me away enough to inspire me to keep it in the air. Thanks for the video. 73 de w8tam

[@W1VLF]

Thomas.. I have a couple of home brew "active" E probe type antenna as well. I will be doing a video about those in the future

[@YO2LDK]

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 !

[@Tump2010]

Just found this video, I found it extremely interesting.

[@TheSemtexCow]

Thanks, very informative. Learnt quite a bit there.

[@r.johnson5077]

Thanks for another informative video.

[@kennymanchester]

Excellent demonstration and definitely worth the time. Now I need to go hit my junk boxes to measure up some coils!

[@W1VLF]

Thank you Kenny appreciate the comments

[@elmofeneken4364]

Very very interesting. Enjoyed it.

[@mikemoore3639]

Awesome content. I learned something quite useful. Thank you for doing this video.

[@W1VLF]

Thank you Mike 73's W1VLF

[@smyrtgyz]

Thank you for your time INTERESTED!!!

[@wifi404]

I learned something today!! Good video, thanks!

[@W1VLF]

Hi ,,That is the best compliment I could be given,,, Thank you

[@SupernovaSpence]

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

[@jhallo7740]

Great video. I made a loop antenna for medium wave band, and coupled that to a old tube radio. It works perfect, and reception is with the loop, much better than the ferrite antenne inside the radio. The radio has also long wave band, and i am thinking of building a second loop for lw reception. Or is it possible to use the medium wave loop, for longwave reception, and ad some capacitance accros the air tuning capacitor? I'm not sure, but i think the gain losses will be to high with that sollution?

[@theDaftman]

Old video i know but very interesting. Thank you for your work and uploading.

[@W1VLF]

Thank you Sir... I am glad you enjoyed it. W1VLF

[@ratmadness4858]

thanks! this cleared up so many things I didn't understand.

[@W1VLF]

Hey Alright!! Thanks for letting me know. Glad it helped.!! W1VLF

[@bharatshetty9560]

Very interesting and informative, thanks for sharing.

[@gilbertmawera5319]

Very clear and informative.

[@W1VLF]

Thank you.. Look for a another video on determining 'Q" factor coming soon

[@gonebamboo4116]

Very worthwhile. Thanks much

[@SevenFortyOne]

Great Info - thanks Paul!

[@W1VLF]

Thank you Sir!!

[@karlD1963]

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.

[@chronobot2001]

Great video. Very practical.

[@W1VLF]

Thank you Electroman!! W1VLF

[@paulschmolke188]

Nice demo! Tempted to hit the surplus store and grab that scope and generator. Loop antennas are fascinating. KE5TJ. 73

[@W1VLF]

Go for it! W1VLF

[@chuck0837]

You’re awesome ! Thank you for your videos

[@ArnavRanjekar]

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

[@sincerelyyours7538]

Good video, but how did you design your loops to begin with? Measuring them after they've been built is, as you described, easy. But I'd like to get at least ballpark close to a particular frequency on paper before I buy the materials to make one. How is that done?

[@nicholashamblin3600]

Excellent video i learned allot. Thanks

[@marcoperez3189]

Thanks for your video. It really is very interesting and educational.

[@W1VLF]

Hi Marco.. Thanks for taking the time to say so. It gives me encouragement to make more videos.73's W1VLF

[@johnmorris9711]

thanks, I am about to make a large loop, tunable to a m broadcast, to experiment around co channel interference,, I recently noticed 1 of my table radios performs nearly as well as my communication receivers, not too well, trying to get KNX in LA, the loop coupling is what I was looking for, - john in glenns ferry- CET since 1969

[@diego.alienigena]

really interesting video, I was looking for this information, thanks! and 73's from LU7HDM

[@jeff-73]

What do you think of the VNA mini devices in place of your big scope? (i have never seen those big scopes at flea markets for $25)

[@GaryRowlands]

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

[@glk001]

Interesting and well done video...I've caught a few of your experiments or tutorials and live just down the road and would enjoy seeing and learning...I'll have to become a neighbor...lol...

[@W1VLF]

Hi I would nice to have another radio friend.. where is just down the road?

[@kaifunderud6101]

Thank You. I found it interesting and entertaining.

[@Ilhaanize]

Sir thank you for this great explanation!

[@W1VLF]

Thank you .. I appreciate you taking the time to comment.

[@viswesh713]

great information sir, thank you so much

[@Muggs828]

"The group W bench"! LMAO!!! This was really helpful to a (not yet) new ham. Thank you!

[@untraditional6235]

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$, sadly at my location the cheapest oscilloscope and signal generator starting from 200$.

[@AdamEbelgccengineering]

What is the right oscillioscope and RF generator that I need to do this? All I have is a digital L/C meter on my work bench.

[@catalinalb1722]

Hello Sir, great video. The coupling loop should have a specific length?

[@W1VLF]

Nope.. not at all.. It just needs to be big enough to couple energy into the main loop so you can see it on the scope.

[@poseypapusdiazfamily4630]

I guess you can make loops for 80 meters etc too? Would they be ok for tx too?

[@jaxxx66]

great stuff 👍

[@ivanp3880]

Great video very informative thank u

[@jacoubejarul5017]

Thank you very much ,very important video👍🏽

[@W1VLF]

Thank you Sir.. Very glad t was helpful W1VLF

[@jacoubejarul5017]

@@W1VLF yes is very helpful thank you again

[@poseypapusdiazfamily4630]

Great knowledge

[@morpher44]

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.

[@coialruis1747]

Thanks Sir, How we find resonant frequency for a line ? ( Antenna)

[@davidfuzatto]

Ótimo vídeo! Parabéns pela maneira clara e objetiva de ensinar. Grato. Aqui de Coronel Xavier Chaves, MG brasil.

[@W1VLF]

Obrigado Coronel. Agradeço você assistir o vídeo e comentar. Espero que esta tradução esteja ok para você ler.

[@davidfuzatto]

@@W1VLF Coronel, é o nome da cidade onde vivo. Coronel Xavier Chaves-MG- Brasil. A tradução ficou perfeita!

[@W1VLF]

@@davidfuzatto Obrigado !!

[@tylerpattison2560]

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

[@RogierYou]

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?

[@fredmoore1197]

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.

[@kevinwingfield2007]

Enjoyed video. Question: Could someone put a capacitor in series to reduce the coil's effective self capacitance and raise its resonant frequency?

[@W1VLF]

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

[@JohnDoe-mg7ht]

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?

[@robblerouser5657]

I like the "Bite Me!" sign in the background.

[@W1VLF]

I forgot I had that up there!!!!! LOL ....

[@timmack2415]

So, for the AM bcb, what frequency do you aim for?

[@khemrajramsamooj9334]

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?

[@ko2fjb]

Is there any way to determine what ferrite rod value is if you didn't buy it.