interesting through hole filter - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: January 09, 2025, 06:29:04 am
content: I found this guy, it looks like a three terminal capacitor that is combined with ferrite beads into a single componenthttps://www.amazon.com/HELZCDNL-Electronic-Accessories-Capacitors-Three-Terminal/dp/B0CX56G5N7Is that what those tubes are?

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: January 09, 2025, 07:56:25 am
content: It's a T filter.They are quite common in RF equipment (at least in the SMD form)https://www.mouser.com/ProductDetail/Murata-Electronics/NFE61HT181C2A9L?qs=Q2Rsuhc0qGv2qQlzESy0hw%3D%3D

author: coppercone2
author_rank: Super Contributor
timestamp: January 09, 2025, 10:07:29 pm
content: I know of those but I never saw it combined in through hole like that, I think it looks like a jet packa real one I mean, not helicopter men, or turbine man, but a rocket man

author: TimFox
author_rank: Super Contributor
timestamp: January 09, 2025, 10:18:55 pm
content: Feed-through capacitors that go through holes in panels or chassis are quite common for RF filtering.For example:https://www.ctscorp.com/Files/Brochures/EMC/CTS-Tusonix-Feedthrough-Filters-Catalog.pdfIn the same packages (either threaded or solder-in), there are more complex filters with inductors as well as capacitors.Also, that packaging can be obtained for insertion into Dsub and similar connectors.Cylindrical feed-through and "button" capacitors have less parasitic series inductance than normal two-terminal capacitors.The first time I saw a four-terminal surface mount capacitor during a design review at work, I mistook it for the cylindrical type (due to the symbol used on the schematic) and wondered how it fit onto the PCB.That style has the current path down the long dimension of the 0805 or other rectangle, with two ground pads on the centers of the long sides, which also reduces the inductance.For example:https://www.mouser.com/datasheet/2/281/1/NFMJMPC226D0E3_0_370-3158700.pdf

author: coppercone2
author_rank: Super Contributor
timestamp: January 09, 2025, 10:22:19 pm
content: Oh yeah I have seen the feedthroughs too. But the only three terminal capacitor I ever heard of was just a three terminal disk capacitor that used the wire for inductance.I saw the feedthroguh DSUB and I thought its scary, they always rip out of the plastic. I feel like a part seated there can break. Ferrite plate seems OK though, they have them with just ferrite plates. Maybe its a better structure then just soldering a 0402 in there though, I never saw the insides.It makes me think of something, that is what if you used a binocular core on a through hole part? Possibly nonsensical but it would fit in there. It seems like this filter would also possible work as some kind of notch circuit in the 2 bead form. For a binocular bead I don't know what it could be used for. Some kind of common mode notch ? Almost makes me want to turn on a simulator to see what happens there

author: coppercone2
author_rank: Super Contributor
timestamp: April 24, 2025, 02:44:10 am
content: what is thishttps://www.mouser.com/ProductDetail/Tusonix-CTS/4100-053LF?qs=MAKYsf4oimlerDQ2xGGQhA%3D%3DIs that a 2 part distributed capacitor that is the 'shield' over a axial inductor (wire)?Or is it some how really lumped?

author: TimFox
author_rank: Super Contributor
timestamp: April 24, 2025, 02:51:00 am
content: Quote from: coppercone2 on April 24, 2025, 02:44:10 amNo: it should be two discrete capacitors with an inductor (coil) between them.Note the largish capacitance values: 5 and 10 nF.The shield is because this unit is designed to mount above a PCB with three through-holes, while the "feedthrough" type capacitor or filter is designed to penetrate a conductive panel or layer.

author: coppercone2
author_rank: Super Contributor
timestamp: April 24, 2025, 02:53:30 am
content: The one in the beginning of the thread is a feed through too (PCB Mount), they are not advertised for common modehttps://www.digikey.com/en/products/detail/murata-electronics/DSS1NB32A103Q91A/5018211I don't understand the tubular construction, but it the weird one is a CLC and the other ones that look like jet packs are LCL

author: coppercone2
author_rank: Super Contributor
timestamp: April 24, 2025, 02:57:28 am
content: Is the red part the capacitor, the tube in middle is a shield for the inductor and a short for the ground and the other terminal of the of the capacitors then?So the capacitor material looks like a red tube shape (slid over the wire like a ferrite bead, but its a capacitor

author: coppercone2
author_rank: Super Contributor
timestamp: April 24, 2025, 03:09:18 am
content: Is it this? The two ceramic capacitor beads have metalized edges, one of which is bonded to the wire going through them, and the other one is bonded in the middle to the grounded tube ?That makes a C L C circuit throughOr instead of a metal tube, it could be a outer surface surface metalized ferrite tube, so you have a inductor bead between two capacitor beads, that also functions as a path for the capacitors to ground (on the ends and outside surface)??

author: ftg
author_rank: Frequent Contributor
timestamp: April 28, 2025, 04:32:37 pm
content: Quote from: coppercone2 on April 24, 2025, 02:44:10 amThat's a feed through cap being used as a THT component.If you ignore the center pin, it looks like a normal solder-in feed feedthrough meant for metal tin plate boxes.I have seen these used to isolate RF stages from each oer in old VHF radios.

author: coppercone2
author_rank: Super Contributor
timestamp: April 28, 2025, 08:18:04 pm
content: I thought feed through only had distributed cap, this is cap and inductor and cap

author: TimFox
author_rank: Super Contributor
timestamp: April 28, 2025, 08:34:53 pm
content: Quote from: coppercone2 on April 28, 2025, 08:18:04 pmA feed-through capacitor has a tubular dielectric capacitor between the center wire and the cylindrical sleeve.Because of the radial field lines, it has a usefully high self-resonant frequency, besides being useful for penetrating metal walls (power connections to box interiors, etc.)However, the same overall package is often built with a series inductor (coil) to form a "pi" filter, packaged in the useful threaded or solder-in shell, for better RF isolation on power connections, etc.https://www.engineering.com/the-engineers-guide-to-feedthrough-capacitors/Another useful style of rotationally-symmetric capacitor that seems to have disappeared is the "button mica", which can be packaged for either stand-off or feed-through purposes, also with high self-resonant frequency.Typically, the outer (ground) surface of the disc-shaped object is soldered to a surface with a suitable hole drilled for it.Now found only on eBay and surplus dealers:https://www.surplussales.com/items/90-laser-optics/2926-alumina-ceramics/124968-250-pf-silver-mica-button-capacitor/

author: vk6zgo
author_rank: Super Contributor
timestamp: April 28, 2025, 11:55:52 pm
content: Quote from: coppercone2 on April 24, 2025, 02:44:10 amMouser's AI lies---the one in this picture is just a plain old feed through capacitor, with the centre connection being (at normal frequencies), a "piece of wire", which is connected to one side of the capacitor, with the outer tube/ring being the other connection.I have seen equipment where such feed throughs were used as ordinary capacitors, with only one end of the centre conductor connected. (They must have had a lot of them in stock).The OP one could be just about anything, including a ceramic resonator.

author: coppercone2
author_rank: Super Contributor
timestamp: April 29, 2025, 12:31:03 am
content: what AI?https://www.mouser.com/datasheet/2/96/4100-053-1132911.pdfit has a data sheet drawingp TYPE LOW PASS FILTE

author: TimFox
author_rank: Super Contributor
timestamp: April 29, 2025, 03:34:44 am
content: Quote from: vk6zgo on April 28, 2025, 11:55:52 pmThe Tusonix datasheet linked from the Mouser page is definitely a C-L-C filter, not merely a capacitor.https://www.mouser.com/datasheet/2/96/4100-053-1132911.pdf

author: coppercone2
author_rank: Super Contributor
timestamp: April 29, 2025, 03:57:44 am
content: Having the middle part be metalized ceramic ferrite would IMO be brilliant because then its a shield, ground point and bead. There could even be a coil inside with its own tiny ferrite rod to make it even more inductive (magnetically shielded inductor)for 37 dollars.......Maybe its meant to be a feed through for a shield that is attached to the PCB. That way you can have the board soldered together, and then put the shield on with a cutout for the part. If you tried to use a bulkhead fitting for that, you would have a very tricky solder joint to make on the inside (lead from feedthrough in shield)I wondered about how to this before, I thought maybe to just make a notch in the shield, so you can put it over a ferrite bead (in the middle). This would be better though, because you could even solder it to the shield can, especially if you form some notches on it that mate with the flange of the CLC filter. Having a part just sit in a shield notch seems like a low cost solution.I mean, unless you use a shield with a spring finger lid.But I think it still has benefits over compression bolt or spring finger shields, since its soldered you don't need 50 bolts, gold plating, leakage through spring fingers, torque concerns, contact integrity concerns, vias getting crushed, etc.Shields really seem like an area of design where it can get really janky/creative quick if you don't have special parts.... and that is a place where you can quickly get solutions that do work but have severe mechanical/durability/assembly problems. And tons of undefined construction methods get used in situations like this.