fridge magnet iron loaded flexible sheeting? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: October 21, 2021, 08:07:25 pm
content: 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.

author: coppercone2
author_rank: Super Contributor
timestamp: October 21, 2021, 09:26:02 pm
content: they also sell tape in the hardware store like that, itsvery weak but good enough for a paper

author: 3roomlab
author_rank: Frequent Contributor
timestamp: October 22, 2021, 01:23:34 am
content: Quote from: cdev on October 21, 2021, 08:07:25 pmi 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

author: coppercone2
author_rank: Super Contributor
timestamp: October 23, 2021, 04:15:49 am
content: I think I have a roll of that tape, if you can design a experiment I can try it up to 300Mhzputting 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 desirableSomething 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

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 23, 2021, 07:47:18 am
content: I doubt it. The material is magnetically hard, it should have little permeability. Likely losses are dominated by dielectric (what's the carrier, rubber? PVC? And the ferrite should still have (di)electric losses).Tim

author: coppercone2
author_rank: Super Contributor
timestamp: October 23, 2021, 05:29:37 pm
content: how about just rolling it up into a swiss roll and then winding wire around it to measure it like a normal rod inductor of the same size with a known core (film canister big ones) from a good manufacturer. it should be geometrically close to a cylinder. Or winding it into a swiss roll and sticking a insulated wire through the middle like its a big ass ferrite bead and measuring that in a RLC meter or impedance analyzer. That should give you power performance and RF performance, after all, it is some kind of ferrite bead I think, since its just a strait pass of wire through it, it should be fairly RF friendlier.Can those parameters be used to select a screening/antireflection material?Otherwise how about the normal test, two horns aimed at each other through a reflector, then coat the reflector with the material (its just a 45 degree plate) to see how much the signal propagation changes.Building your own inductor core at custom sizes by wrapping tape together like a wasp hive is interesting also. Particularly if its wrapped with epoxy (possibly thermoset) so you can get a good quality part afterwards. I guess it would be the closest thing you can get to nanocrystaline tape from the HW store.

author: cdev
author_rank: Super Contributor
timestamp: October 23, 2021, 05:42:54 pm
content: Quote from: 3roomlab on October 22, 2021, 01:23:34 amI was thinking about damping resonances in instruments where they become problematic. For example, in the nanoVNA2 discussion threads it emerged that using a metal case for a nanovna2 introduced resonances between 3-4.5 GHz, that were caused by the presence and size of the case. Without a metal case, no problem. The metal cased units would likely benefit greatly from a damper, but the costs of these materials is significant.I have had similar problems with low noise amplifiers.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 01, 2021, 09:23:59 am
content: Someone had a problem with a 10 Meter mobile amp oscillating. Multiple attempts to assure the integrity of all the coax, antenna, grounding, power cables and connections did not helpHe wrapped it in sticky padded aluminum tape from the hardware store, that solved the problem We were surprised at the success of this endeavour but did see it work. The tape itself was not grounded, Apparently it changed the resonance of the case. The foam padding created a gap between the metal cans and the outside aluminum.Again,we did not think it would work and were surprised at the result.