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31 material. At 30MHz, they’ll be similar but, 31 should be superior below that due to the higher permeability.

That'll work for ETD or EE core sets as well! The calculation for the cross sectional area and magnetic path length are a little different but, the concept is the same. One thing to be cautious of is the air gap in cores like this. If the surfaces are well finished, this can be negligible. If the surfaces are uneven or rough, this can skew the inductance value very low compared to what the material perm would otherwise be.

One trick would be to use several smaller cores stacked together or in parallel. Lower cross-section cores will typically provide lower losses over a wider range of frequencies (to a point) but, they cannot handle the same sort of flux density as a large core. The ideal core would be something like a long tube shape. Thin walls but, high length the get the cross section number back up. A stack of small cores can be used for a similar effect.

They definitely use geometric tricks to manipulate and dissipate the fields that hit the walls. The ferrites in these are generally just flat absorbers behind the e field absorber foam )typically where the fun geometries come in. In ferrites, we usually talk about dimensional resonance in the sense of standing wave generation inside the magnetic cross section. This is still an area of a lot of research to better understand but, the effect seems somewhat similar to skin effect in conductors.

In most of our engineering kits we do label the cores, or at least color code dot them with the material!

Send your request to ferrites@fair-rite.com and we can send that to you!

Can you provide an electronic copy for download?

@@amham48 Unfortunately as of now we do not distribute the poster electronically. We will make an announcement if and when that is available 🙂

@@FairRiteProductsCorp I would love to have one of those posters for our electronics lab as well, if that's possible! Also, really appreciate your podcast series, and I like that you aren't taking yourself too seriously and can joke around as well, looks like you're having fun working, and I wish more workplaces would show that! ;)

@@larspetersson7168 Thank you!! Email ferrites@fair-rite.com and we can get you a poster sent asap and a Signal Solution Kit if you do not have one already!

Typically the saturation characteristics will be slightly softer. It depends a lot on how well they are made. The tighter the tolerances and the flatter the mating surfaces, the more they will just act like a solid core.

My knee jerk answer not being a transformer designer is that they can be very similar. The difference will be in how they are wound. Toroids have the ability to be sector wound or with overlapping primary and secondary windings whereas, multi-aperture (also known as binocular or balun) cores are really only able to be wound with "stacked" windings.

I've only ever seen 6 aperture cores used in suppression though, I suppose you could make some unusual transformers out of them. A 6 aperture core could be useful for something like a matrix transformer.

52 or 61 material should be the best choices. Generally, you want to select the material that has the highest permeability at your start frequency (12MHz in this case). I mentioned 61 incase the power levels are higher. 61 won't provide as good coupling as 52 but, it will be quite a bit lower loss.

Differential-mode noise is generally not as common as common-mode noise (pun intended). Often it is as simple as there only being one conductor present to "pick up" radiated noise from something. Having just a single conductor out in the open or spread far away from others isn't usually the norm in most electronics. In the context of on a circuit board, differential mode noise will be seen more frequently. Important to note, that differential mode ferrites will suppress differential and common-mode noise. A common-mode configuration will only suppress common-mode noise.-Mike

@@FairRiteProductsCorp Thanks. True, in typical harness configuration, you have multiple wires, and maybe one wire has common mode emissions on it, but I guess that noise will couple onto the other adjacent wires in that harness bundle. How could you identify common mode on that single wire ? Use a current clamp and analyzer? You could save money buying a smaller ferrite for that one wire than buying a larger ferrite to go over the whole harness. But I've never seen that solution before.

@@brucetouzel6484 Cores used in differential mode (single wire) will suppress both common and differential mode noise. The thing with using a core in differential mode is that the primary signal "sees" it. You have to make sure the core isn't adding significant impedance to the thing you DON'T want to suppress. The other thing that needs to be considered in differential mode is the current. Too much and the core saturates and provides no impedance. Smaller diameter cores will require less current to saturate. Differential noise would be most easily measured by checking both lines independently and together. If it shows up on either line independently but, not together, That'll be differential mode noise.

We will be covering this in a video coming soon!

We will be covering this in a video coming soon!

From an electrical standpoint, there is no difference between using a toroid and a multi-aperture core. In some cases, especially when operating QRP, the smaller form factor of a multi-ap core is desirable from a convenience standpoint.

So, if the toroid and the snap-it (the ferrite bit inside) are the same size, the impedance would be almost the same. Toroid would be very slightly higher due to not having a gap. Multiple turns through either would have the same effect of Ω*N^2 at lower frequencies

For adhesives, cyanoacrylate works very well on ferrite cores. Gluing a broken core back can work with a few caveats. If the fracture or break is running across the magnetic path (O.D.-I.D. on a toroid for example), there is going to be some loss of effective permeability. This loss will be proportionately larger on higher permeability materials than lower ones. Whether or not the core remains functional really depends on what it's being used for and how sensitive the application is to values like inductance, coupling coefficient, impedance, etc... As far as larger than needed cores, it again will depend on what it is being used for. Large cores will have higher inductance values typically and produce lower core losses due to the reduction in flux density from the greater cross sectional area. Windings can be spaced apart further leading to lower interwinding capacitance (can be good or bad). A negative is that ferrites (all ferrites) are prone to dimensional resonance beyond some frequency when the cross section gets too massive leading to higher relative losses and reduced bandwidth than a smaller toroid of the same material. That last one isn't yet well quantified and it's significance will vary a lot by size, material, and frequency.

A combination of materials would be the most helpful but, it is difficult to truly assess how effective they will be at suppressing an EMP. 75 material covers from around 200kHz into the low MHz range, 44 material covers several MHz to several hundred MHz and 61 goes from several MHz to several GHz. That combination would likely be most effective. How well they work is going to depend on just how high the induced currents are. If they are too great, the cores can saturate and won't provide much attenuation.

43 material would cover that range with relatively low core losses. At the lower frequencies (say 400kHz and below), a higher permeability MnZn core like 78 material would likely perform better. This would come at the expense of higher frequency performance however.- Mike

​@@FairRiteProductsCorpthank you guys.. The whole science behind this is something of a 'dark art' for me at the mo. I do have some toroidals at home that i think are type 77 as i can measure surface resistance across them, as opposed to type 43s which are labelled and measure open circuit. I had used these 43's for matching my flag antennas which measure anything from 200ohm to 1000ohms across the BCband, but decide to replace them with the other unknown ones. I have a nanoVNA and i think this will enable me to identify the characteristics of the unidentified toroidals. Bottom line is, do u think type 77 will offer a noticeable improvement over a type 43 of similar size and turns ratios?

If the 43 cores are already working at low frequency without getting excessively hot, I wouldn't expect a massive improvement. At low power levels, the 77 should provide lower insertion loss due to the higher permeability. At high power, low frequency, the 77 should have lower core losses. Higher frequencies at higher power levels, the 77 may see excessive core heating due to the losses. @@vincentstevens5048

@@FairRiteProductsCorp thank you guys for making an effort to answer my questions. I neglected to mention I'm not transmitting. Its purely for my receive antennas. Im mainly interested in long distance MW reception, but i have the problem of being very close to a BC transmitter, so i am trying various solutions involving different antennas, but matching these to 50ohm is a priority. Thus the use of baluns/ununs etc etc

As a general statement, 67 material has the most stable permeability over temperature. Depending on the exact temperature range, there could be other materials that are more stable at particular temperature ranges.

@@FairRiteProductsCorp thank you for your response!

Hi Michael, feel free to apply at fair-rite.com and have a wonderful new year 🙂

The effective perm formula for toroids won’t be too helpful due to the difficulty in calculating the magnetic path length on something like a rod. What’s the total rod length and inductance? Do you have an approximate size for the gaps? Feel free to send your answers to ferrites@fair-rite.com and Mike will walk you through the best he can 🙂

@@FairRiteProductsCorp Thank you -- will do!