Electronics > RF, Microwave, Ham Radio

fridge magnet iron loaded flexible sheeting?

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cdev:
Can it be used as a poor mans RF absorbent material?

I am talking about the material that merchants use to make printable fridge magnets (at least here they do) that they give you. Its cuttable and may even stick to some (steel) metal cases.

I dont know, it just seems as if it may be useful to cut resonances and cheap.

coppercone2:
they also sell tape in the hardware store like that, itsvery weak but good enough for a paper

3roomlab:

--- Quote from: cdev on October 21, 2021, 08:07:25 pm ---Can it be used as a poor mans RF absorbent material?

I am talking about the material that merchants use to make printable fridge magnets (at least here they do) that they give you. Its cuttable and may even stick to some (steel) metal cases.

I dont know, it just seems as if it may be useful to cut resonances and cheap.

--- End quote ---

i have considered the same as you. i have not tried. but it seems very plausible. i tried some random femm just for magnetics and it looks ok to my untrained eye. i think the soft sheet workability is a plus as opposed to sheet metal working in certain situations. i saw online stores that sell it in large per meter rolls 1mm to 3mm

evb149:
"rf absorbent" doesn't mean much unless you get into specifics.
Is that 100 kHz, 1MHz, 10MHz, 100 MHz, 10 GHz, ?
The behavior of basically anything will change a lot vs. frequency even if the
loss is broadband, at least the sheet thickness compared to the wavelength and propagation mode will matter a lot.

If you're interested in reducing the EMI coming from inside a chassis getting to the outside you can go a long way with standard EMC design practices for the chassis design and cabling and PCBAs etc.

If you want to keep outside fields out then again chassis / PCBA design principles will help a lot, but it also depends on wavelength, 50 Hz, 5 MHz, 500 MHz, 5 GHz all have different challenges.

If you're trying to cut down EM coming from inside a chassis interfering with other circuits  also in that chassis then what you can't otherwise prevent from creating fields or isolate by geometry / distance / shielding you can try to absorb, sure, anything helps.

But you can use metal sheets, metal foils, metal loaded paints, etc.  Those will reflect though may also absorb significantly depending on the composition (e.g. copper vs. ferromagnetic etc.)

Some use carbon loaded antistatic foams for a cheap lossy material for inside of small chassis.

The ferrite loaded foams are still going to be frequency selective based on composition, density, thickness, etc. but it's worth a try, easy enough to check out with any basic setup you might cobble together.

Just think about the properties of proper RF ferrite beads or ferrite toroids vs. powdered iron etc. several very different materials / properties are available and you get several ranges of ferrite beads depending on loss curve vs. frequency etc.

coppercone2:
I think I have a roll of that tape, if you can design a experiment I can try it up to 300Mhz

putting a sheet between a signal and receiver coil (like NFC coils?) might work as a test?

I thought about it because of ferrite rod antennas, big ones, where you have the option of using ribbon cable as a shield, but I still am not fully sure how ferrite material around the coil acts like, so its possible to make a rib-cage of magnetic tape to experiment with ferrite rod antenna characteristics, if it has a different from solid conductor metal strip material, or to find out if sticking it on top of strip material might do something desirable

Something tells me a proper test is laying it on the inside of a horn antenna or TEM cell or something (waveguide?) maybe, to see how much signal gets out? My horns all have polarization layers or optics on them though

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