RF shield boxes, where to get them? - Page 1
Forum section: electronics / rf-microwave

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 14, 2018, 03:50:54 pm
content: So I've been browsing some blogs and forum posts and often see these small metal boxes used for RF projects. I was wondering where to get them, or if there is a nice source of these things?A general project box isOften to large. I'm talking about boxes on the order of 5 cm x 5 cm x 2.5 cm (for you imperial folk, that is 2 inch x 2 inch x 1 inch, give or take).Open from the front. By this I mean if we were to take a box of cereal as standin, the side that opens on the project box is the "lid" of the cereal box. I want the "big" side to open, ie, where on the cereal box it would have all the pretty branding and pictures as it's the part that faces you.In case you want an example, although this one is already quite tall compared to what I had in mind (from hackaday):Is there any store I can get them for reasonable prices? They would be nice to make some projects in that are noise sensitive.On a related note: I prefer not to make resonant cavities. What is a good source of RF absorbing foam?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 14, 2018, 04:03:40 pm
content: I'm going to reply to myself here in case others wonder the same at a later point:A good first source seems to be searching for stuff like "guitar stomp box enclosure" or "guitar effects pedal box" or similar. They are similar to what I am looking for. Ideally I would like them squarer so they look more like a "real" box used by minicircuits and the lot, but it is a start.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: January 14, 2018, 05:09:44 pm
content: http://www.pomonaelectronics.com/index.php?i=prodsub&parent=BOX&cat=BOXCVR&getDetails=0

author: David Hess
author_rank: Super Contributor
timestamp: January 14, 2018, 06:27:49 pm
content: I prefer to build them out of doubled sided copper clad board as shown below. If the edges overlap, then the seams may be soldered on both sides making them very strong and the continuous copper surface on the inside and outside allows for easy connections to ground unlike if zinc or aluminum is used. The extended overlap as shown can be used to protect bulkhead parts as shown.

author: jpanhalt
author_rank: Super Contributor
timestamp: January 14, 2018, 06:40:05 pm
content: http://g3nyk.ham-radio-op.net/componen.htmhttp://www.tekoenclosures.com/en/products/family/RF(I like the ones with lots of tiny friction fingers)http://www.schubert-gehaeuse.de/And last but not least:http://hammondmfg.com/John

author: yl3akb
author_rank: Regular Contributor
timestamp: January 14, 2018, 06:47:35 pm
content: I can recommend this shop:https://www.rf-microwave.com/en/metallic-boxes-with-two-covers/368/They also sell RF absorbing materials:https://www.rf-microwave.com/en/microwave-absorbing-materials/377/

author: xygor
author_rank: Regular Contributor
timestamp: January 14, 2018, 07:15:06 pm
content: Another option: Nickel conductive paint can turn (almost) any box into a shielded box.

author: cdev
author_rank: Super Contributor
timestamp: January 14, 2018, 07:31:06 pm
content: Copper tape is good in a pinch also. And works pretty well. Even under or over cardboard (under is often best /better from a grounding point of view, you can also make a little square under where the connector exits) You can coat cardboard with copper tape, then cut it to size, then put the box together and add small dabs of solder (this is when the copper is on the inside of the box so the outside looks ugly) to get it to hold its basic shape, see if the PCB fits, if it does then add more solder and the RF connectors. Ive recently used the type of RF connectors that combine both edge mount PCB and a longer SMA (they look odd because the SMA is so long) so there is both a PCB connection and an around the egress type connection. This kind of design is not particularly good looking (unless you could find good looking cardboard) but it is functionally fine, as long as the equipment stays indoors. Ive tried using foam core and foam core is great for antenna prototyping (its dielectric constant is "1") but for obvious reasons foam core is not good for boxes that need more than just the tiniest amount of actual soldering. So - no good for RF boxes you want to solder to give them better connectivity. The foam melts. Use cardboard.The big plus is that doing this you can make your box the perfect size for your PCB, so it fits snugly. This may improve some devices performance.Adding a box thats too big conversely may degrade performance.

author: cdev
author_rank: Super Contributor
timestamp: January 14, 2018, 07:39:09 pm
content: Where can one get the perforated, highly bendable - very light tin sheeting used for solder on RF shielding around tuners, etc. on a PCB? Say if I want to have a small shielded box around a portion of my PCB, say to isolate different parts of it?Its a 1970s kind of building style but it is helpful.

author: cdev
author_rank: Super Contributor
timestamp: January 14, 2018, 07:49:43 pm
content: Very nice but also expensive for what they are, IMHO.Quote from: ahbushnell on January 14, 2018, 05:09:44 pm

author: cdev
author_rank: Super Contributor
timestamp: January 14, 2018, 07:58:54 pm
content: Get a big used activated charcoal filter (BRITA water filters after they are used up work well and contain a lot of material) use as much as you can stir/squeeze into the rapidly hardening foam but don't spend too much time or it will harden before its done..get "great stuff" spray foam. and a small container you have absolutely no use for afterward because it will be permanently ruined. get a cheap spatula and also put on rubber gloves (nitrile work well and are cheap) wear clothes you wouldn't mind ruining because this is messy.. Spread out newspapers. The charcoal should be dry but the weather can be humid, it helps the foam set. Ideally you should do this outdoors.. Not when its windy, either, you have to work fast.. basically you spray out the foam, mix in as much activated charcoal as it can hold, stir it well and then put it into your enclosure with the spatula doing your best not to get it on yourself. Try to make it as dense as possible before it goes into the enclosure and then make it flat. Also your holes etc should already be drilled. Then let it set. Then clean it.Another alternative, use the foam that they sell for ESD protection, as much of it as will fit, squeezing it so it makes contact with the enclosures walls.Quote from: TheUnnamedNewbie on January 14, 2018, 03:50:54 pm

author: xaxaxa
author_rank: Regular Contributor
timestamp: January 15, 2018, 05:48:09 am
content: there are shitloads of these on aliexpress, in various dimensions; just search "aluminum enclosure"

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 15, 2018, 08:01:09 am
content: Quote from: xaxaxa on January 15, 2018, 05:48:09 amWhen you look for aluminium enclosure on aliexpress. most of what you get is the clasical project box where the "front" opens, and not the "top". The thing is that if you want to put a board in with connectors and such, you need the "top" to open up so you can get to the connectors for soldering etc.The diy approach is nice for prototyping but I would like my end product to be in a nicer box. I'm gonna have a look around for of the options listed here.Thanks all for the tips.

author: medical-nerd
author_rank: Regular Contributor
timestamp: January 15, 2018, 11:56:50 am
content: HiyaHave you considered diecast boxes such as :https://www.canford.co.uk/EDDYSTONE-DIECAST-BOXESI have found the smaller ones to be very useful, you can also then add rf fingers to the case.Note - I have not bought from this seller, just using as an example.Cheers

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 15, 2018, 03:45:37 pm
content: Quote from: medical-nerd on January 15, 2018, 11:56:50 amDiecast boxes were on the list. I found that on Aliexpress search keys like "Guitar effects box" or such show up a lot of similar results. Will look at getting a few from various sellers to see if they are any good.

author: rhb
author_rank: Super Contributor
timestamp: January 15, 2018, 09:15:19 pm
content: Most HVAC shops have little scraps of galvanized duct metal they will give you for free. Make or buy a small bending brake and you have cheap, easy to solder custom boxes. Not a substitute for a Hammond or Pomona die cast box, but if what you want is internal shielding compartments it will work just fine. Otherwise scrap food tins, though those are often coated in addition to the tin plate. Danish cookie tins are convenient stock for small shields.If you find a good source for feed thru capacitors I'd love to know. China requires buying 500 of one capacitance and Mouser et al are $5-6 each :-(

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: January 15, 2018, 10:04:02 pm
content: Real RF enclosures?<http://www.fischerelektronik.de/web_fischer/de_DE/Geh%C3%A4use/M1.11/Geh%C3%A4use%20f%C3%BCr%20die%20HF-Technik/PG/GHFN_E/search.xhtml><http://www.schott.com/german/news/press.html?NID=com4541><https://telemeter.info/de/hf-mikrowellentechnik/gehause-und-frasteile/frasgehause>cheers, Gerhard

author: Bud
author_rank: Super Contributor
timestamp: January 15, 2018, 10:42:52 pm
content: Quote from: rhb on January 15, 2018, 09:15:19 pmTry the abovementioned link to rf-microwave.com, they have a section with feedthru caps at different price ranges.

author: cdev
author_rank: Super Contributor
timestamp: January 16, 2018, 12:52:43 am
content: danssmallpartsandkits.com has feed through caps,but they are old stock,but now there are better feed throughs out there that integrate an series inductor and a capacitor.

author: cdev
author_rank: Super Contributor
timestamp: January 16, 2018, 02:22:00 am
content: What's the best way to handle if it your PCB contains a gain stage, like an LNA and your LNA is too small to fit snugly in the case, avoiding resonances? I try to create a sort of enlargement of the PCB to the box's walls with copper flashing.

author: whalphen
author_rank: Regular Contributor
timestamp: January 27, 2018, 02:10:24 am
content: As others have mentioned, they are available on AliExpress. For a long time I wondered why I couldn't find any there. Then I discovered they are all called 'stomp boxes' by the vendors there. Search on that and you can find some very good prices. I ordered a few from different suppliers and found them all to be good quality diecast aluminum boxes that match the dimensions of the Hammond boxes with similar part numbers.However, if you work with very small components, such as surface mount, and often need shielded enclosures I suggest trying copper pipe. I often design PCBs to fit in copper pipe. The pipe is easy to cut to length, and is readily available in a range of diameters and thicknesses. I order copper pipe 'test caps' from large plumbing suppliers. These are pipe caps that are thin, flat on the end, and easy to drill and solder. I typically use SMA connectors and they are easy to fit onto a test cap. I've also used the test caps as RF shields mounted on PCBs. They are a lot cheaper than commercially available RF shields.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: January 29, 2018, 05:09:27 pm
content: Quote from: whalphen on January 27, 2018, 02:10:24 amI love this idea, and it seems so simple and obvious! Thanks a lot for sharing!

author: djsb
author_rank: Super Contributor
timestamp: February 02, 2019, 04:01:46 pm
content: Quote from: whalphen on January 27, 2018, 02:10:24 amWhat do you use to pass the connections through the copper end cap? Is it a feed through of some kind? Any details would be appreciated. Thanks.David.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: February 03, 2019, 02:56:56 am
content: Boxes from Digikey.

author: cdev
author_rank: Super Contributor
timestamp: February 03, 2019, 04:25:38 pm
content: It very much depends on what signal needs to pass through. A feed through capacitor is basically a bypass capacitor that shunts AC above a certain frequency to ground more effectively than a single bypass cap because its designed to stop RF. I use them for DC, like a power line. Now I have some slightly better ones that also contain an inductor. So they are a low pass filter, they are designed to eliminate RF.Some other methods are used to filter wires coming in and out. Ferrite materials, Use coaxial connectors for RF. Also devices may use simple soldering posts to provide a good place to attach a ground for say the negative lead.Quote from: djsb on February 02, 2019, 04:01:46 pmWhat are you trying to do?

author: bd139
author_rank: Super Contributor
timestamp: February 03, 2019, 04:40:06 pm
content: I snap up any Pomona boxes I find on ebay or I use hammond boxes and build the circuit in the lid:Either that or PCB boxes which are fine for HF. This return loss bridge is good to about 200MHz (or is it the terminators that suck?) according to my MFJ-259B which was a surprise.Pomona wins though if I can find enough of the damn things