I just googled "EMP frequency spectrum". A quick look suggests that amplitude is down significantly in the vhf range, so given the size of an ammo can, it would probably be ok even if the lid is connected at only one point. However, it seems that there is significant spectral content up into the GHz range, and I would feel safer with contact all around the edge. Anyway, an ammo can is rather heavy. It would be nice to be able to bring the shielding container along on a camping trip without re-packing in a lighter container. If one accepts the need to re-pack, one might as well use a bigger container such as a full size trash can, and use it to shield a variety of electronic devices. In my mind I see some kind of camping food container made of aluminum that was used in my childhood. I guess that product has been displaced by plastic containers long ago. OTOH there are now companies that specialize in selling mesh or conductive fabric for turning your whole bedroom into a Faraday cage. Could there be a market for custom radio cases that incorporate a layer of such shielding material?
73, Erik K7TV -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Clay Autery Sent: Wednesday, September 06, 2017 11:42 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Radio storage cases Yes, all true milspec cans have gaskets for water-tight fit... However... 1) Note that all cans I have seen have a metal lip that overlaps on 2-3 sides, plus the latch, PLUS the pinned hinge. 2) IF you see to it that there is a conductive path via the top to the can body via the hinge and/or latch(es), AND/OR add a bonding wire between the lid and can, ...you have an effective electrical faraday cage up to the frequency whose wave-length is smaller than the larges continuous gap between adjacent metal surfaces at worst... AND because the on most cans the pulse would have to turn corners or a 180 even then, still a pretty effective shield. You could always test it yourself. <smile> ______________________ Clay Autery, KY5G On 9/6/2017 1:31 PM, Dale Chayes wrote: > The true military (metal) ammo cans are (supposed to) have a rubber gasket between the top and the body. (Just checked one, it does.) Perhaps that would allow some EM leakage? > > It would not be hard to scrape a bit of paint off and solder or silver solder a ground strap (or foil) bridge between the lid and the body (perhaps on the inside for durability) but Im not sure if that solves the (potential non?) problem? > > -Dale/KB1ZKD > > > > On Sep 6, 2017, at 14:00 , Walter Underwood <wun...@wunderwood.org> wrote: > >> A military ammo box should work. They are pretty cheap, too. You could buff off the paint to get good contact around the lid. >> >> http://www.cabelas.com/product/shooting/ammunition/ammunition-boxes|/ >> pc/104792580/c/104691780/sc/522363780/cabelas-mil-spec-ammo-can/16112 >> 84.uts?slotId=0<http://www.cabelas.com/product/shooting/ammunition/am >> munition-boxes%7C/pc/104792580/c/104691780/sc/522363780/cabelas-mil-s >> pec-ammo-can/1611284.uts?slotId=0> >> >> wunder > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net Please help support this email > list: http://www.qsl.net/donate.html Message delivered to > k...@montac.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to ebasil...@cox.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
