FYI, aluminum flashing is lacquered! And maybe anodized too. Be prepared to clean connections before taping the stuff!
Also use conductive adhesive, not the common hardware store stuff -- you won't get a reliable connection otherwise.
Reference: I set up a quick EFT test plane this way. Sanding the edges was an unfortunate loss of time, but still better than taking the EUT into a testing lab.
If you want to do this with hardware store parts and minimum effort, I recommend the 0.025" (or so) squares of aluminum they usually stock. Although they don't usually stock enough of them to do more than a little testing, not at all a whole room. HVAC sources may be attractive in that case (galvanized steel is somewhat solderable, and will block a bit of magnetic field too).
Tim
I measured 260 pF per square inch for the thin adhesive aluminum foil HVAC tape. So that's 12.5 nF along an 8 ft seam using 2" tape. At 1 MHz that's 12.7 ohms. With a 4 x 8 ft wide sheet of aluminum taped all around it's about 4 ohms. 3M makes 6" wide tape which would be about 1.3 ohms. That's not as good as soldered copper sheet, but it's a *lot* cheaper.
Galvanized steel with an overlay of aluminum would address both low frequency H field shielding and high frequency E field shielding. In my case the electronics bench will probably move into a windowless metal building. So before I build anything, I'll be testing various constructions with a spectrum analyzer.
I measured 260 pF per square inch for the thin adhesive aluminum foil HVAC tape. So that's 12.5 nF along an 8 ft seam using 2" tape. At 1 MHz that's 12.7 ohms. With a 4 x 8 ft wide sheet of aluminum taped all around it's about 4 ohms. 3M makes 6" wide tape which would be about 1.3 ohms. That's not as good as soldered copper sheet, but it's a *lot* cheaper.
Galvanized steel with an overlay of aluminum would address both low frequency H field shielding and high frequency E field shielding. In my case the electronics bench will probably move into a windowless metal building. So before I build anything, I'll be testing various constructions with a spectrum analyzer.
Aha, numbers! Which now invites discussion of attenuation: how much is required? Enough to just take the edge off, or regulatory test chamber levels? Or nuclear EMP for that matter!
Mind that, that ~10 ohm impedance is distributed along the seam, so at wavelengths on par with the seam length, the effective impedance is higher. It becomes a thin slot rather than a parallel plate capacitor. At still higher frequencies, it becomes a thin waveguide, and transmission will peak at 1/2 wave multiples of the overlap length (or half tape width, if tape is applied evenly over the joints), so, up in the GHz.
Impedance of free space is 377 ohms, so -- very roughly ballparkly speaking -- ~10 ohm impedances will have a ~37x attenuation, or ~32dB. Maybe not much for the effort required -- but definitely noticeable!
Speaking of GHz, I wonder what the dielectric loss tangent of that adhesive is. Probably not great, in which case the attenuation would still be okay. (It looks like acrylic adhesive in flex circuits is actually slightly better than epoxy. If it's a rubber based adhesive, I have no idea.)
Tim
I'm a 65 year old nerd who was tormented by high RF fields while pursuing the PhD I did not get in Austin. So it's more an exercise in "because I can" than anything else. I will actually measure what I need before I do it. My goal is to be able to make low level measurements with confidence that they are not corrupted by QRM.
I built a 120 dB gain 3 transistor DC amplifier when I was in Austin. After I squelched the oscillations at 150-300 KHz by bypassing the electrolytics with small ceramics I could listen to the FM station a few miles away by holding my finger near the unterminated inputs. Trying to measure things accurately was maddening.
I decided to stop at 3 GHz for most of my gear. That covers the 2.4 GHz ISM/WiFi band. I'm in rural Arkansas (population of town 7500, county 27,000) so I think it unlikely that I have significant problems except the the 1 kw AM station about 2 miles away. That clobbers my SDRplay RSP2 but it's daytime only so I do get some reprieve. So I don't really expect I need much, if anything. I rather suspect I'm generating most of the noise myself. I bought two of Henry Ott's books, and Ralph Morrison's latest ed. I recently discovered I already had Morrison's 1st ed.
I've known that RF was *interesting* for many years. I used to taunt EE undergrads with big egos. One of them told me I could not pass 2nd semester physics (E&M) because "this was where they weeded out the engineers" and I had an undergraduate degree in English lit. I had the high score on the final, an 89. The class average was 45. I *so* wished I could have put a PostIt that said "English major" next to my score. Only grade I ever actually cared about. Not because i was trying for it, but because I did it. I joked to my TA when I turned in my exam, did he get the license number of the truck that hit me. I solved a capacitor problem on the exam from first principle. But I always thought grades were largely irrelevant. What I learned was what mattered. That outlook has stood the test of many years.
I filed, scraped and lapped a 0.75" x 1" x 3.125" block of 6061 aluminum flat to 6-8 tenths and parallel to about half that just because I'd never done that and had not done that type of bench work in many years. It was also easier than setting up to use my milling machine which would only have gotten me through the file stage anyway. Having learned to flat file a work piece, it's amazing how quickly I can do that on a small piece.
I got "Electromagnetic Compatibility Engineering" by Henry Ott based on someone's suggestion. I'm quite pleased with it. Ott has been in the business for many years and presents lots of data from tests his consulting firm made. For example the effectiveness of various shielding materials for a pair of solenoidal coils. I've not read a lot of it yet, but it looks to me like a good investment, The older book by Ott grew into this one and the name was changed. I bought Ralph Morrison's book, but it's a little disappointing at $70.
Just so you understand my perspective in saying that. I have a 5000+ volume personal technical library. If I *thought* a book might be useful in my job I bought it so I'd have it on hand if the need arose. I got a lot of work that way because if there was a rumor of something I would know more than most after a few evenings reading. I spent most of my career as a contract employee. If I could buy a book for $150 and by doing so knock a half day off of what I had to bill my client I considered it great bargain. I saved the client several times the cost of the book. I typically billed 35-37 hours per week. The perception of management was that I worked much more than that. So even at a high hourly rate, I was a bargain.
My library covers a lot more than merely subjects related to oil exploration. But that willingness to invest in my own abilities made me a brand name. Contracts found me. My last one was a 2 year gig with the acquiring company following the takeover of the company where I'd worked for 6 years. That job found me when a former boss when we were at another oil company left a message on a friend's answering machine saying he "was looking for a Reg type".