The remarkable new RF-suppressing impregnated soft plastic better than ferrite

[6SN7WGTB]

Just bought some chinese shyte which came with a USB cable.

It had the characteristic 'ferrite' moulded on to it.

Sawed it off and it's just soft plastic.

Or maybe it is an innovative class-leading RF-suppressing impregnated soft composite...?

[silverback]

possibly carbonyl iron added to the plastic or silicon rubber.

[6SN7WGTB]

Looking at it through a loupe I could not see any texture suggesting it may be metallic or crystalline.

In any event such a material would be a very poor substitute for a ferrite core - and doesn't the very usefulness of ferrite depend on the density of magnetic particles?

[T3sl4co1l]

Well no need to speculate, does a magnet stick to it or nah

[mag_therm]

Soft magnetic plastics have been used for 30 years in induction heating (Fluxtrol)
Also  other providers for UHF and in food industry etc.
Permeability is low ( 20 ~ 30 or so), but effectiveness can be gained back by the formability close to the conductor.
(Fridge magnets use the hard magnetic material.)

[6SN7WGTB]

Needless to say it is not magnetic at all...

[Neganur]

Ferrite is not supposed to stick to magnets, or?

[T3sl4co1l]

(They got scammed.)

(Or got what they expected, and didn't pay much for it either, I don't know.)

But suffice it to say, yes, there are people putting those on as solid moldings just to make it look right, and customers rarely know the difference -- or have the means to test.

Tim

[6SN7WGTB]

Came free with something but since it's chinese, knew it would be shyte, sawed it open, and sure enough the chinese are scamming us at every opportunity.

[coppercone2]

jajajajank

its not just china, look at the DIY injection molding techniques they developed in the dirt streets of pakistan, powered by fire and a old drill press.

Also, high end looking black foam, made in plywood boxes.


I literarly watched a video that showed a small operation with 2-3 people making power cord moldings, they light up a small wood fire in a box, put a extruder on top of it for a bit, then they put it up in a manual press with some plastic beads and lever it. It had some clever thing to hold a soldered power cable so you get the "quality prongs". 

How do they make the hopper you ask? its a pipe filled with beads, with a sheet of material under neath. YOu simply align it and pull the sheet out and bobs your uncle. I wonder how the insulation resistance is on wood fired pakistan style power cords?

Wood fired, like high end pizza.   


You don't even need a chinese factory, its like a few guys in a dirt floor shed


oh yeah, its similar to how they make the chinese popcorn in the mini kettle cannon that you put over a wood fire


and the molded stuff too, spin it manually over... a wood fire! or tires I guess whatever that is, probobly not wood. Those are some high quality barrels, ready to spill industrial chemicals when they break because of poor temperature control during manufacture.


Here is what i would call a higher end operation



It makes me nervous though, I don't know much about PVC pipes, but for power cords, like the place should be clean, so you don't get some metal junk in the plastic. You can't do mass production in a place like that and expect results


I am suspicious that for pipe, pressure is too low in the mold, the proper machines are like 10x bigger

[6SN7WGTB]

I watched a similar video showing an Indian chap melting down old aluminium pots in his yard and scrap to cast a new gearbox shell for his scooter.

Yes, it will be poor quality, but an outstanding example of innovation and lack of waste.

Conversely from china we get brand new useless waste.

[coppercone2]

bro its totally good for some crap that can't start a electrical fire. I don't want my power cords made like that, its going to kill people

[mag_therm]

Looking at it through a loupe I could not see any texture suggesting it may be metallic or crystalline.

In any event such a material would be a very poor substitute for a ferrite core - and doesn't the very usefulness of ferrite depend on the density of magnetic particles?

Ordinary ferrites  mostly become ineffective at UHF. **

Look at data sheet for Kemet FlEx Suppressor UHF grades EFG and EFA
https://www.kemet.com/en/us/technical-resources/ready-to-flex.html
Now available from Digi Key https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/57/Noise_Suppression_Sheet.pdf
Page 14 shows some uses including cable and flat cable wrap.
The UHF suppression is by high magnetic losses ( Ur'' ) .

The DC permeability of these materials is in range 20 to 70.
I doubt that would feel magnetic by a hand held magnet test.

For example austenitic stainless 18/8 or 304 etc start out at 1.002 but ends up at 20 to 50 after cold work
That doesn't exhibit  feel force by hand held magnet. Compare low carbon steel which may have an effective DC permeability in the 1000's +.

An LCR meter with an empty test coil might show whether your part is ferromagnetic or not when slid into inside an empty coil.

** I have type 61 Ferrite cores on ham radio USB and antenna cables and aluminum case , but the RFI from the Netgear NightHawk 2.4, 5GHz comes blasting through into one of the SDR.

[ejeffrey]

It had the characteristic 'ferrite' moulded on to it.

Sawed it off and it's just soft plastic.

This sort of thing has me wonder why exactly they bother.  It's not like the vast majority of end users carry about the presence or absence of a ferrite.  While the plastic over molding is cheap, presumably it's cheaper to do nothing?  Was it the factory trying to trick the distributor?  Was the product EMI tested and failed without the ferrite and they need to ship it looking the same as tested?  It might be overstock from another product, but then why did they do it for another product?

[T3sl4co1l]

The DC permeability of these materials is in range 20 to 70.
I doubt that would feel magnetic by a hand held magnet test.

What is there to doubt? The magnetic path length of a typical thing-stuck-to-magnet is maybe 1/2 to 1/10 the air gap length of the bare magnet, i.e., mu_eff is 2-10 even if \$\mu_r \rightarrow \infty\$.  Materials of comparable permeability are absolutely "sticky" in feel.

It's when it's very low, under 2 maybe, that it becomes quite slight.

Tim

[mag_therm]

What is there to doubt? The magnetic path length of a typical thing-stuck-to-magnet is maybe 1/2 to 1/10 the air gap length of the bare magnet, i.e., mu_eff is 2-10 even if \$\mu_r \rightarrow \infty\$.  Materials of comparable permeability are absolutely "sticky" in feel.

It's when it's very low, under 2 maybe, that it becomes quite slight.

Tim

This morning I hung a string of ~ 20 small neo magnets on a  1 metre long thread hanging from vice to near floor.
I tested with a aus_stainless plate that has been bent through 90 degrees. The plate attracted the magnet most strongly at the bend.
It would gently start to pull the magnets from about 25mm.
I read that aus_ss work hardens to form a low level of martensite giving permeabilities around 20.
The UTS of cold worked ss is almost a linear relation to Ur.

I have ordered a sheet of Kemet Flex Suppressor type EFA to see if some cable wraps of it augment the existing type 61 toroids around the cables
to a troublesome (at 144, 432 MHz)  SDR here.

[T3sl4co1l]

Well now I'm curious.  Because, I gave a concise, physically relevant, realistic explanation.  It seems I have failed to land that point; but I do not understand how it has failed.

How convincing did you find my argument?  Perhaps it wasn't understood; should more background be given?  Perhaps it's too technical; should it be simplified?

Perhaps your recollection is more authoritative to you; any argument to the contrary, faces a steep uphill battle in that case -- we all give priority to what we've internalized.  Do you remember where it came from?  Are you sure you remember it clearly--?

Perhaps you aren't recalling at all, but have a source to hand; could you provide a citation?

If a matter of authoritativeness, do you have any particular reason to doubt my knowledge on magnetism -- whether in general terms, or relative to someone you might've discussed this topic with (or an author you've read) before?  Or perhaps not in terms of academic authority, but social -- did you hear it from someone you took to be a peer? Or who was in a leadership/managerial role?

I am something of an authority on magnetism on this forum -- by several users' admission, I mean; I don't say this to stroke ego, honestly I don't care, but I do wish to communicate clearly -- if not, and if I'm not being taken authoritatively, that means I'm reaching fewer people, and I should probably change my strategy -- or failing that, just spend my time on more productive endeavors. Hey, teaching's not for everyone.

But also, I digress; I ask many questions because I want to be precise; and, in case you don't have ready answers for most of them, perhaps a few will land.  This carries the downside of making the whole thing seem much more important than it really is (again... just curious).  It also carries the risk of coming off as hypercritical, accusatory, "Just Asking Questions(TM)", for which I'll apologize in advance: that wasn't the point.  Well maybe a little, maybe asking just one or two of these would be enough to jog the mind, question assumptions, and change your conclusion--that's fine; but I still wonder if I should've said something different.

Anyway, that's enough 'tism for one day...

----

At risk of tainting the response to the above (honestly-- I am curious!), and because I'll probably forget about it if I defer it until the next reply -- I have found a reference that looks current and authoritative:
https://www.matweb.com/search/DataSheet.aspx?MatGUID=60afb49104a9421ab23f7dfc2767d62e
(or even better, from the source: https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/austenitic/ati_302_304_304l_305_tds_en2_v1.pdf )
which is quite low as I expected.

Also, for my part, I took a 35µ powder core (#8) here, and it feels as strong as steel against a hard drive magnet.  Maybe even stronger, but that's probably just because it has larger diameter (less curvature, less air gap, more area "in contact") and thicker section than the steel pipe I'm comparing to.  (Though there's not much field inside the pipe, so I think section thickness isn't the issue here.)  Considering the flat vs. cylinder geometry, I would guess this is on the low side (like ~1/10th magnetic path length), but 35 > 10 so it's still strong.  Likewise, a 10µ powder core (#2) feels decidedly weak, *maybe* about half the force, maybe less, but I'm just holding things in my hands here.  It is a somewhat smaller core, but not small enough to make that big a difference; it's definitely less "sticky", and if it's about 10µ out of 10µ_eff = 5µ total, that would definitely be in the right ballpark.

Tim

[coppercone2]

I took my RF ferrite sample box and all of the beads are strongly attracted to a big magnet including ones that have curve in GHz, but they are SMD, I don't know if its nickel. I imagine they would all be attracted to magnets though

[fourfathom]

I took one of my clamp-on mix-43 ferrite cores and it was quite attracted to a ceramic refrigerator magnet.  The molded plastic cylinder on an unknown-origin USB cable was also noticeably attracted.  FWIW.

[thm_w]

Product?
Photo?

The only use case would be helping something pass EMC testing thats kind of on the edge of passing. So, that would only matter if they compliance tested the cheap product you bought for NA standards, which they may or may not have.

So, even though its fake, you can't really prove its a problem without proving this thing will fail EMC compliance.

[G0HZU]

If it helps, I've got various sheets of adhesive backed RF absorber material here. This stuff is grey in colour and it looks and feels a bit like a bendy plastic sheet. It can be anything from 0.2mm thick to over 1mm thick and can be purchased in A4 sized sheets. It is similar to a bendy cheese slice except it is grey in colour, it feels like soft plastic and it doesn't taste as nice.

If a magnet is held near it then it does get attracted to the magnet. It's mainly used as an absorbing material that can be cut into shape with scissors and stuck (like a tile) to the underside of a screened lid for example. It works over a very wide frequency range.

However, I doubt this stuff would be used on consumer cables because it is extremely expensive. There are thin versions of it that can be wrapped around cables like adhesive tape although I don't have stuff this thin.

[coppercone2]

i have a piece of rf foam from RF chamber construction trimmings, I don't know what it is, the spec was 3GHz chamber, its flat not pyramids

It is not attracted to magnets, but I suspect its just carbon. I tried using the 100lb magnet from a magnetic welding clamp (one broke, one was saved)

[coppercone2]

If it helps, I've got various sheets of adhesive backed RF absorber material here. This stuff is grey in colour and it looks and feels a bit like a bendy plastic sheet. It can be anything from 0.2mm thick to over 1mm thick and can be purchased in A4 sized sheets. It is similar to a bendy cheese slice except it is grey in colour, it feels like soft plastic and it doesn't taste as nice.

If a magnet is held near it then it does get attracted to the magnet. It's mainly used as an absorbing material that can be cut into shape with scissors and stuck (like a tile) to the underside of a screened lid for example. It works over a very wide frequency range.

However, I doubt this stuff would be used on consumer cables because it is extremely expensive. There are thin versions of it that can be wrapped around cables like adhesive tape although I don't have stuff this thin.

it sounds like you can shield a ribbon cable with this