Path: csiph.com!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Don Kuenz Newsgroups: sci.electronics.design Subject: Re: EMI problems Date: Wed, 21 Jun 2017 02:53:02 -0000 (UTC) Organization: A noiseless patient Spider Lines: 71 Distribution: world Message-ID: <20170620a@crcomp.net> References: <21n3kcdugfo0cf3uup7qtp333eri70pmgp@4ax.com> <1ae40009-0204-fa1e-718d-fc736fec43d1@electrooptical.net> Injection-Date: Wed, 21 Jun 2017 02:53:02 -0000 (UTC) Injection-Info: mx02.eternal-september.org; posting-host="64f003209aa45d89bce0a2743a81965c"; logging-data="28621"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/moyBDCdmNw5Q0XUllNpBC" Cancel-Lock: sha1:pb3iW6tzMzmzCITefBZ2JmNDyrU= Xref: csiph.com sci.electronics.design:465093 Phil Hobbs wrote: > On 06/15/2017 03:28 AM, o pere o wrote: >> On 15/06/17 03:01, John Larkin wrote: >>> On Wed, 14 Jun 2017 20:05:21 -0400, Martin Riddle >>> wrote: >>> >>>> On Wed, 14 Jun 2017 16:09:43 -0700, John Larkin >>>> wrote: >>>> >>>>> >>>>> >>>>> I designed this little photodiode amp and I'm trying to measure its >>>>> output noise. All we can see on a spectrum analyser is radio and TV >>>>> stations. >>>>> >>>>> https://dl.dropboxusercontent.com/u/53724080/Otis/EMI/Sutro.JPG >>>>> >>>>> The *output* of the amp needs to be around 10 nV/rootHz. >>>>> >>>>> The *output* of the amp needs to be around 10 nV/rootHz. >>>>> >>>>> The DUT output is 100 ohm differential, which makes it harder. So we >>>>> took one of our standard products, an x100 1GHz amplifier, and hacked >>>>> a wideband transformer into the front end. Then I stuffed the DUT and >>>>> the X100 amp into a custom-machined shielded enclosure. >>>>> >>>>> https://dl.dropboxusercontent.com/u/53724080/Bypassing/E2_EMI_Encllosure.JPG >>>>> >>>>> >>>>> The DUT is the smaller extruded box. There's enough gain that I can >>>>> use a scope to measure RMS noise voltage directly. >>>>> >>>>> Those are really nice shield cans, but before you can use them you >>>>> have to find a way to dispose of the filler materials that they come >>>>> with. >>>> >>>> You can still get the 'Charles Chips' 1 lb tin. It's a tad bigger if >>>> you need more room. >>>> >>>> Cheer >>> >>> A square can would be better. It's a little weird bolting connectors >>> into the round one. This needs research. >>> >>> >> >> You can get squares... even without filler material! >> >> https://es.aliexpress.com/store/product/Size-180x130x72mm-tin-box-food-tin-can-cookies-box-biscuit-metal-box-gift-container-storage-box/713943_32297655507.html >> >> >> Pere > > For smaller stuff, I have a bin full of unused 70-mm nickel-plated steel > film cans that I got from Surplus Shed. You put the connectors in the > lid. ;) > > Clean paint cans work well too--there's a tea place in Maryland that > ships their teas in them. Empty Altoids tins also work and have an iconic design language. In this case the connectors work best on the side. Altoids jelly bean mixer http://crcomp.net/ee/Altoids%20jelly%20bean%20mixer/ Thank you, -- Don, KB7RPU