How To Measure Ferrites using a NanoVNA

[@HamRadioDX]

More NanoVNA videos ⬇ Using a NanoVNA to Fix Our Repeater Coverage: kzbin.info/www/bejne/Zp61fICti7ODjsU How Long Is Your Coax? Testing with NanoVNA: kzbin.info/www/bejne/mYLOc4B6j5p0nrM

[@JamieStuff]

You are on the right track with the resonance theory about your "3 turn" coil. This is evidenced by the fact that you are showing +6 dB on 2m, so you definitely have some E/I phase games going on. All coils have a self-resonant point, due to the L of the coil, and the (parasitic) C vetween the turns of the coil. I would expect a MUCH different result if you spread the turns around the ferrite. The Smith chart should explain what's going on. I might dig out my NanoVNA and do some experimenting. (Edit: I'm an EE, though it's been a few decades since I studied this.)

[@silverXnoise]

Came here to say this exact thing. The Smith chart can be enabled simultaneously with logmag, and will almost certainly shed some light on what’s happening at that point.

[@k6usy]

I was amazed when I was able to troubleshoot a coax switch on 1296 with a NanoVNA. The alpha delta switch I am using is rated to 1300Mhz but not all ports act the same, just had to move my antennas to the better ports.

[@johnwest7993]

My NanoVNA and TinySA allowed me to finally see all the things I couldn't see for the first 30 years of my career because I couldn't afford a network analyzer and spectrum analyzer, and besides, they were big and heavy and ran on AC power. Now I have it all in my pocket.

[@amham48]

Terrific! Best demo I've seen on ferrites.

[@HamRadioDX]

Thanks!

[@craigwestlake7362]

My NanoVNA arrives next week! Another rabbit hole to explore.. Can’t wait now to experiment. Thanks Hayden.

[@HamRadioDX]

Hope you enjoy it! Have fun experimenting mate

[@williamscott8397]

I have a device inbound. I really appreciate your instructional style. Keep pumping out relevant and helpful content!

[@HamRadioDX]

Thanks, will do!

[@jerrym1183]

When you are doing an amplitude measurement like this especially at higher 144 MHz it really helps the accuracy and dynamic range of the measurement to be sure to ground the "shield" of your RF in/out coaxial test leads together at the coaxial end of where your Ferrite under test is happening, this will give greater accuracy especially for 10/6/2 meters. Good Stuff!!

[@deanhutchinson3848]

By adding more turns to the ferrite core you create a capacitor with the wire. This will then bypass the higher frequencies. Depending on the core material you also tune the core to a lower frequency by adding more turns. The normal recommended maximum number of turns is about 3max

[@jaym1301]

I think the reason the small mix 31 ferrite beads were better than the snap-ons was the smaller inside diameter of the beads. There was more of the ferrite material surrounding the wire on all sides vs, on one side for those big ones. I bet two or three snap-ons with just large enough of an inside diameter to allow two passes of cable through and still be able to snap closed would solve the real-life RFI issue.

[@laurencerilling5873]

Also the extra passes through the big one had a similar benefit

[@mike94560]

I set display scale to 3 so it is easier to find 3dB points. Nice video.

[@LifeAtTerminalVelocity]

Dude you just solved a problem for me! Testing this was on my To Do list for the northern winter. Now I'm just going to implement your solution and be done with it.

[@HamRadioDX]

Thanks Carlos. I've ordered one of the testing rigs from Halibut Electronics. That will be good for testing chokes around coax too. Do you have some RFI issues?

[@RobCanada]

Thanks for the video. I've had a NanoVNA for a while collecting dust as I have a bunch of professional antenna analysers but I am finding these videos fasinanting as to what you can do with these tiny units and it's spuring me to get mine out and play. I look forward to the next installment :)

[@johnwest7993]

Professionals use network analyzers on antennas, not hobbyist gear labeled "Antenna Analyzer." I've designed, built, and tuned numerous antennas with my network analyzer and I don't even own an 'antenna analyzer'. The NanoVNA is the perfect antenna tool, and costs next to nothing. The only thing it won't do is field strength and radiation patterns, and that's what I have a TinySA for. This is a great time for antenna work for both hobbyists and pros, when you can get all of the tools you need for under $200, including some attenuators.

[@ka6psdrbeswick709]

Awsome demonstration , very thorough.

[@HamRadioDX]

Thank you!

[@hewking]

really good video - can you or anybody else please explain why common mode travells on the outer shield and not on the inside conductor?

[@earlyadapter643]

This setup aims at measuring the S21 (with the little calibration issues, see the comments below), meaning how much attenuation you get into a 50 Ohm input, and it is also possible to convert the S21 with its phase into a complex impedance. However, the interference to your radio equipment comes from what is radiated by the piece of cable that is hanging around behind the ferrite, and for this, same as in a balun, you dont know its input impedance which in general is complex. Therefore, it is not a good approach to build just a sufficiently huge inductance for the common mode, because the impedance of the cable acting as an antenna might be capacitive and unluckily cancel the huge inductance of the ferrite coil at the frequency of interest. Therefore, the strategy used in building Baluns is to make a coil with a self resonance at the frequency of interest, making it a huge, ideally purely real, impedance. I think that for the RFI suppression, the same strategy should be used so you should look at S21 with its phase to see whether your coil is a good real open circuit at the frequency of interest. I wonder by the way to what criteria the RFI filters for example in switching power supplies are designed.

[@bitemykrank1970]

Very interesting video Hayden. I will have to make up some test leads, I have a box of ferrites of many sizes and mixes, some are a known mix, other are unknown. This is a simple method to show if they will work on a particular frequency, even if the mix is supposed to be for different frequencies. It would be nice to see a side by side of say, 43, 52, 62 and 74 mixes as they pertain to the HF end of the spectrum. These seem to be the most commonly used and recommended mixes for CMC and RFI choking. It would also be interesting to see the side by side of ferrite against iron core, as A LOT of guys seem to find 52 mix iron core toroids are the best for 20m antenna's, but I haven't seen any iron cores used for suppression chokes as yet. Problem of course is having the toroid's to test, as they can be VERY expensive items for some types. I only have one iron core toroid, I bought for a particular antenna build that Alex VK2PRC designed and has had GREAT success with, using an Iron core 52 mix toroid and some wire., he gets 40m and 20m from the same feedpoint. I know this bit is off topic, but I added it anyway.

[@rjordans]

Nice presentation, if you want some more graphs similar to what the manufacturer of ferrites provides you can use the nanovna-saver software on your computer and plot the complex impedance

[@HamRadioDX]

Yes I was playing with that last night! Seeing the R+jX is very handy

[@rjordans]

@@HamRadioDX it can also give you permittivity if you want to make inductors or transformers

[@Hank_W6IR]

Great video Hayden!

[@HamRadioDX]

Thanks Hank 👍

[@y_x2]

You should use an half wavelength of wire and move it along the cable to see the effect.

[@StreakyP]

OK if you are working on a spot frequency but if you are looking at say working across 3-30MHz then your half wave is anything between 50m & 5m so unless you have stretchy cable you wont be able to use a half wave across all the freq band you are interested in

[@acestudioscouk-Ace-G0ACE]

This is fascinating and not always what you expect! Thanks Hayden. Did you find much difference in ferrite positioning? When you had one at each end and one in the middle, if you had put two at one end and one at the other, would that affect the reading?

[@youtubeaccount931]

thiis something ive been wanting to see, thanks. I have a pile of random unknown ferrites that i'd like to profile. I had similar result watching noise supression of multiple turns of an ethernet cable, turns were better than multiple ferrites, and more turns had diminishing returns, usually two or three turns did the most work and any more than that had minimal or no benefit. Also thanks for explaining why you do the crossover when winding, i've seen everyone do it but never heard an explanation.

[@HamRadioDX]

Glad it was helpful! Thanks 👍

[@ernestb.2377]

Very useful, thanks! The question about "too many" turns on one core and less attenuation on higher frequencies, or even +dB's. Maybe you have too much capacity between the turns?

[@HamRadioDX]

Good point!

[@ernestb.2377]

@@HamRadioDX But you can test that hypothesis by increasing or reducing the distance between the turns, I suppose.

[@richardsierakowski1623]

Excellent info. Thanks.

[@michaelcarey]

Great video Hayden. I've been contemplating attacking my home Ethernet cabling with ferrite clamps to help reduce noise/birdies/whistles it creates on HF. This is something I've lived with for a while now (I've done a KZbin video about it years ago). Since upgrading to Cat6 (over Cat5E) cables through the house it is better.

[@HamRadioDX]

I did forget to mention in the video I bought a common mode choke test rig from Halibut Electronics in the US on Friday… so looking forward to getting that to use - electronics.halibut.com/product/common-mode-current-choke-test-rig/ I put some clamps on my (new) router and WiFi AP after I suspected they were causing some noise on HF. Coincidentally the noise level has dropped - but time will tell if it has made a permanent improvement, even 6m is quieter! Thanks Michael 👍

[@jez4491]

Fascinating video. How many turns have you been able to do on coax cables? considering they're quite 'thick', I wouldn't have thought you'd be able to get many turns into a ferrite core.

[@HamRadioDX]

RG-58 fits through a couple of times (I think maybe 3) in a 13mm clamp. The ring ferrites are much better suited for making common mode chokes :)

[@LeeMcc_KI5YPR]

I will make loops with a larger radius through the ferrite, and not pull them tight.

[@chasri8358]

thanks for the share very informative. but we cant coil a rg53 or a rg213 around a ferrite for testing. we have to settle for as is! any suggestions!

[@kevin_wb0poh]

Thanks for the demo - and it may explain an issue I'm having with RFI. I use the clamp ons on the DC lines and Data lines of my HF radio, and they work well. That being said, I was continuing with having issues when I run my FT2800 2m mobile run at 70W using the same clamp-on ferrites on the 2800 DC lines. I suspect I will need to do your measurement on their DC lines. Thanks again.

[@HamRadioDX]

Cheers! Yeah see what happens when you test at 2m, might be a bit different perhaps

[@njjensentube]

Like László HA7DN is arguing, I am afraid the celebration has issues, Especially S21, it is radiating, I would take a big ground plane (like 10x10 cm CU) and solder the 2 coax cables shield onto that ground plane, also i would connect the 2 inner cores without the wire for the S21, shorter is better, it would eliminate radiation from the core when you do the S21 CAL. Thanks Niels OZ1CGQ

[@earlyadapter643]

Exactly, the apparently positive gain of the multi-turn coil comes from the wrong calibration by using the long wire. For the cal the aligator clips should be connected together without anything, or even better, the two coax cladding should go to a base plate and the cores connected together the shortest way.

[@trombabaroque]

Thanks a lot for this great video. I often wondered about the specs of different unknown ferrites, but didnt have the idea to use the vna. This helps to work efficiently and not only by endless try and error, without knowing whats going on exactly. Very interesting the setup with 3 cores at different positions of the wire. I think its worth exploring this a little bit more, to find "hotspots" where the cores are most effective. 73, Stefan/OE6ISP

[@DavidWitkowski]

Nice video. I strongly suggest you stop spinning the center pin of those calibration standards. You want to protect the center pin. Hold the standard in place and rotate only the shield ring.

[@ozvary]

Nice vid! Maybe need a test, 1,2,3 turns without ferrite.

[@Jay2904]

Great video, Hayden. Just wondering, what firmware version do you have loaded on your SAA-2N?

[@HamRadioDX]

Hey mate, I have version v1.3.31

[@arnoldgrubbs2005]

A timely vid Hayden! Thank you. I just got a Common Mode Current Choke Test rig (kit) from Halibut Electronics, and will be starting to play around with some "toe-roids" and un-un's and bal-un transformers. Thanks for the vid!

[@HamRadioDX]

Thanks Arnold, I literally just bought the same test rig! I’m looking forward to getting it and playing some more 👍

[@KU8RLY]

So, for the newbie, can you explain what it is you are trying to suppress.

[@HamRadioDX]

Noise generated by a source at a specific or set of frequencies that radiates down the cable from the source (acting like an antenna)

[@sonarmb]

Eggcellent video young fella😅

[@HamRadioDX]

Thanks!

[@Chris_KI4WCO]

Sooo would it have anything to do with the plastic on the square one? For example on the round one it touches inside and outside . The square only touches the inside. Trying to learn

[@HamRadioDX]

Perhaps 🤔 I do wonder about the distance between coils in the clamp, so do bigger coils make a difference or smaller etc

[@LeeMcc_KI5YPR]

For multiple turns through clamps, I try not to cross the wires. Sometimes not possible. Regardless, there is capactive coupling between the looped wires inside the clamp to create a resonance. How much? 🤷‍♂️

[@HamRadioDX]

Yeah especially Ethernet which is maybe 2 turns before you have to cross over the top?

[@LeeMcc_KI5YPR]

@@HamRadioDX Yes? Although Ethernet is twisted pairs which helps.

[@larslindgren3846]

I really don't understand why most ferrite cores aren't marked with material type, brand and part number. It makes it easy to get them mixed up.

[@phredyh]

Hayden…. That was really helpful…thanx 😁👍

[@HamRadioDX]

Thanks!

[@HamRadioKS-k7j]

Great video Hayden! Thanks for that! 73

[@HamRadioDX]

Thank you too!

[@JayN4GO]

Which mix did you end up using on your Ethernet cable?

[@HamRadioDX]

I ended up ordering a combination of Mix 43 and 31 clamps - still waiting on them arriving

[@akiddoo8113]

Excellent! Thank you

[@mrtechie6810]

You should identify the ferrites and provide links.

[@RixtronixLAB]

Nice video, thank you :)

[@mrtechie6810]

Nice job! Thanks. ❤

[@HA7DN]

Good ideas, but I have a few things to point out. Your setup measures a single inductor as a 2 port device, but you left the GND unconnected, thus you have a very big loop of return current, and I highly doubth that the calibration can compensate for that. I suggest connecting the shields of the 2 probes together, and repeating the experiments to check if anything chantges. At around 12:00 you say and show it measures +6dB transmission, that is clearly wrong, as it would suggest you getting more power out than goes in, and thus indicative of a bad measurement setup. I'm not 100% sure, but maybe it goes away if you fix the probing. At around 19:30, you have unconneccted cables, but the VNA shows nonzero and not flat transmission - also signs of bad probing. You do not measure the ferrites nonlinearity, but that is also a very important effect. The effect of it decreases as power increases, that can cause very strange effects. This might or might not be the reason why increasing the turns does not always help - I would suggest setting the VNA on CW, and checking using a scope how the voltages look.

[@clems6989]

Constantly increasing "Q". Equals constant reduction in bandwidth.....?

[@MauricevdfHermsen]

12:32 that is 1 turn. 73 DE PD4TZ

[@peterderidder6549]

I am not sure if measuring S21 along a 30cm wire on anything higher in frequency than 50Mhz will be correct.

[@HamRadioDX]

Why are you unsure?

[@mrtechie6810]

Doesn't attenuating RF on the network cables interfere with the data flow? Unless you use shielded cable. Or better yet, use fiber! YES! Ferrites attenuate signals on unshielded cable. There is a whole post about this in r/networking: "Ferrite choke on cat5/network cables"....

[@spareiChan]

It will likely reduce the max distance of the cable, Ethernet uses a balanced transmission method via twisted pair so it shouldn't cause an issue beyond just some attenuation.

[@cthoadmin7458]

Hayden's done an entire video on just this subject.

[@mrtechie6810]

@@cthoadmin7458 nice, how do I find it?

[@mrtechie6810]

@@cthoadmin7458 Turns out yes, ferrites attenuate signals on unshielded cable. There is a whole post about this in r/networking: "Ferrite choke on cat5/network cables"....

[@ariebomba]

Nice try. But not accurate, sorry to say. The calibration is the culprit here. Half way your video you start getting positive (!) dB values. That should have alarmed you. It is beter to calibrate the short on S21 with the clips connected to each other, so without the wire. Also would it be a good thing to short the shield of the small coaxes near the clips during calibration and measurement. 73, Arie PA3A

[@lambdaprog]

What you call 1 turn iq actually half a turn. Two turns is 1.5 turn. etc. If you don't complete the turn on the ferrite with the two ends meeting at the same point, it's not a complete turn.

[@briansauk6837]

The overall circuit completes all loops to integers. With that said, the exact geometry of the loops come into play, so the effective “n” may be slightly off from being an integer. If you have a current clamp meter you can see that a single wire through reads almost exactly half of the reading with an additional “full” turn. If it was .5 compared to 1.5 you’d see a 3 x difference.

[@StreakyP]

sorry lambda brian is right. The first wire through IS "one turn" (even though it may look like just a half) as the rest of the circuitry external to it completes the turn. To count the number of turns you ALWAYS just count the number of wires through the centre (& NOT the number of "tight wraps" on the outside as this misses the first turn).

[@danielesteban7897]

A eso le llama medir un ferrite???? Medir un ferrite significa medir la permeabilidad compleja es decir sus componentes real mu prima y su componente imaginaria mu segunda: u = u´ + j u ´´

[@RobBob555]

🎉