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Groups > sci.electronics.design > #464857
| From | Tauno Voipio <tauno.voipio@notused.fi.invalid> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: EMI problems |
| Date | 2017-06-17 21:30 +0300 |
| Organization | A noiseless patient Spider |
| Message-ID | <oi3s8s$jsb$2@dont-email.me> (permalink) |
| References | (3 earlier) <5v88kc569lfa2fb9tj1m0p0ionmj47q7gl@4ax.com> <58c8kctdj2n4ekdv7fhdfbt3q7jg05d4s6@4ax.com> <oehakc58lu3p7c5rtklm73d9kfvvsrm4de@4ax.com> <tvnakcpv7pond0o420kvkh1va44946p9v8@4ax.com> <3trakcdj033er9i9tpaaqc39s5uqrv7pta@4ax.com> |
On 17.6.17 21:07, John Larkin wrote: > On Sat, 17 Jun 2017 10:08:39 -0700, John Larkin > <jjlarkin@highlandtechnology.com> wrote: > >> On Sat, 17 Jun 2017 09:22:20 -0700, Jeff Liebermann <jeffl@cruzio.com> >> wrote: >> >>> On Fri, 16 Jun 2017 12:34:02 -0700, John Larkin >>> <jjlarkin@highland_snip_technology.com> wrote: >>> >>>> There's also a huge amount of lower-frequency noise here, probably >>> >from AC-line powered things in the neighborhood. >>> >>> I see the same thing even in a residential neighborhood in the middle >>> of nowhere. If I unplug various AC powered gadgets around the house, >>> the noise level goes down a little. I can see some of it with a scope >>> connected to the power line through an LISN (Line Impedance >>> Stabilization Network). The really nasty stuff disappears when the >>> sun goes down, which suggests a grid connected solar power system. The >>> problem is that I live in the deep dark forest where such systems are >>> rare. Nothing within a mile radius but I'll keep looking. A line >>> filter usually gets rid of most such noise. If you're located in an >>> industrial area, you might want to investigate what the local PV >>> systems are putting back into the power lines. >>> >>>> This motor controller was making 20 volt spikes in the lab, until we >>>> hacked it. >>>> https://dl.dropboxusercontent.com/u/53724080/Otis/EMI/VFD.JPG >>> >>> Neatly done. No capacitors to form a low pass filter? >> >> The box on the right is a commercial filter, on the input to the >> controller. That helped some. I hacked the toroids in series with the >> outputs, running to the blower on the roof, and that got us down to >> the local noise floor. It's all in metal boxes and conduit! >> >> >>> >>>> Here's the general spectrum: >>>> https://dl.dropboxusercontent.com/u/53724080/Otis/EMI/300MHz.JPG >>>> -28 dBm with just a Pomona lead antenna. >>> >>> 30 MHz/div. TV Ch 2 on the left. FM broadcast band 88-108MHz seems >>> quite strong. One aircraft beacon. Starting at 150Mhz, quite a bit >>> of VHF commercial and public safety signals which quit at about 190MHz >>> with TV channel 7. Methinks if you check the UHF TV and commercial >>> spectrum, the signal levels will higher. >> >> I still want to light an LED from the ambient RF. >> >>> >>> -28dBm is 9mv rms or 25mv p-p into 50 ohms. You should see a 25mv >>> "noise" level on any long wires that can act as an antenna. If you're >>> working with low impedances, not a problem. If you have bandwidth in >>> the FM/VHF region at high impedances, I suggest a screen room, screen >>> box, or differential designs. >> >> We're moving soon, about the same distance from the tower, and we have >> considered some sort of screen room in the basement. But the EMI does >> automagically test our breadboards and products for us. >> >>> >>> BTW, nice Marconi/IFR/Aeroflex/Cobham 2399c spectrum analyzer. I'm >>> jealous. >> >> It's horrible and buggy. It has +-120 Hz spurs, which is like finding >> a roach in your salad. >> >> >> >> >>> >>>>> You might want to calculate the resonant frequency of the Royal Dansk >>>>> cookie can: >>>>> <http://www.rfwireless-world.com/calculators/circular-cavity-resonator-calculator.html> >>>>> If you see a noise peak in that area, it could be something >>>>> oscillating or filtering using the can as a resonator. >>> >>>> I'm OK at 100 MHz. It might make a resonant cavity filter or something >>>> at some higher frequency. >>> >>> Maybe. I've built and seen VHF (150MHz) cavity filters in much >>> smaller cans. Fruit juice cans, paint cans, beer cans, etc all can be >>> made to work. >>> <http://vk4zxi.blogspot.com/2014/08/homebrew-cavity-resonatorduplexer-for.html> >>> All it takes is a center rod between the two ends with a tuning >>> capacitor at one end. A length of insulated wire, soldered to one end >>> of the can, and leaning against the top, forming a capacitor, is all >>> it takes. Small cavities have much less Q, but they still will >>> resonate. I don't have any cookie cans available. I'll get some >>> dimensions at the market and see what happens. >>> >>> Or, you could just frequency sweep the cookie can and see what you >>> get. Just sacrifice some more Danish butter cookies to a worthy >>> cause. >> >> Do I have to? >> >> The SA has a tracking generator; that might be fun. > > Hmmm, how does one do a tracking generator on an FFT-based spectrum > analyzer? Inverse FFT? -- -TV
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EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-14 16:09 -0700
Re: EMI problems Martin Riddle <martin_ridd@verizon.net> - 2017-06-14 20:05 -0400
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-14 18:01 -0700
Re: EMI problems o pere o <me@somewhere.net> - 2017-06-15 09:28 +0200
Re: EMI problems Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-06-15 10:59 -0400
Re: EMI problems Don Kuenz <g@crcomp.net> - 2017-06-21 02:53 +0000
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-15 07:59 -0700
Re: EMI problems George Herold <gherold@teachspin.com> - 2017-06-15 08:07 -0700
Re: EMI problems Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-06-15 11:12 -0400
Re: EMI problems George Herold <gherold@teachspin.com> - 2017-06-15 08:42 -0700
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-15 09:38 -0700
Re: EMI problems Robert Baer <robertbaer@localnet.com> - 2017-06-16 22:06 -0800
Re: EMI problems Jon Elson <jmelson@wustl.edu> - 2017-06-15 14:14 -0500
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-15 13:55 -0700
Re: EMI problems Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-06-15 14:02 -0700
Re: EMI problems Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-06-16 12:43 -0400
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-16 10:11 -0700
Re: EMI problems Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-06-16 13:24 -0400
Re: EMI problems Jeff Liebermann <jeffl@cruzio.com> - 2017-06-16 10:37 -0700
Re: EMI problems Jon Elson <jmelson@wustl.edu> - 2017-06-16 13:31 -0500
Re: EMI problems Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-06-16 14:46 -0400
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-16 12:25 -0700
Re: EMI problems George Herold <gherold@teachspin.com> - 2017-06-16 13:07 -0700
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-16 12:22 -0700
Re: EMI problems upsidedown@downunder.com - 2017-06-16 09:35 +0300
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-16 06:40 -0700
Re: EMI problems Joerg <news@analogconsultants.com> - 2017-06-15 12:27 -0700
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-15 12:47 -0700
Re: EMI problems Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-06-15 12:57 -0700
Re: EMI problems Joerg <news@analogconsultants.com> - 2017-06-15 13:12 -0700
Re: EMI problems Joerg <news@analogconsultants.com> - 2017-06-15 13:03 -0700
Re: EMI problems "Lund-Nielsen, Jorgen" <jorgen.lund-nielsen@xyz123desy.de> - 2017-06-16 08:58 +0200
Re: EMI problems Jeff Liebermann <jeffl@cruzio.com> - 2017-06-16 10:03 -0700
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-16 11:09 -0700
Re: EMI problems Jeff Liebermann <jeffl@cruzio.com> - 2017-06-16 12:06 -0700
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-16 12:34 -0700
Re: EMI problems Jeff Liebermann <jeffl@cruzio.com> - 2017-06-17 09:22 -0700
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-17 10:08 -0700
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-17 11:07 -0700
Re: EMI problems Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-06-17 21:30 +0300
Re: EMI problems pcdhobbs@gmail.com - 2017-06-17 16:34 -0700
Re: EMI problems krw@notreal.com - 2017-06-17 20:44 -0400
Re: EMI problems George Herold <gherold@teachspin.com> - 2017-06-19 06:03 -0700
Re: EMI problems Jeff Liebermann <jeffl@cruzio.com> - 2017-06-18 12:49 -0700
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-18 13:42 -0700
Re: EMI problems Jeff Liebermann <jeffl@cruzio.com> - 2017-06-18 15:50 -0700
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-18 17:15 -0700
Re: EMI problems upsidedown@downunder.com - 2017-06-19 09:39 +0300
Re: EMI problems upsidedown@downunder.com - 2017-06-19 09:48 +0300
Re: EMI problems Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-06-19 12:45 -0400
Re: EMI problems "John Miles, KE5FX" <jmiles@gmail.com> - 2017-06-16 15:30 -0700
Re: EMI problems John Larkin <jjlarkin@highland_snip_technology.com> - 2017-06-16 18:10 -0700
Re: EMI problems Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-06-17 11:08 -0400
Re: EMI problems upsidedown@downunder.com - 2017-06-17 14:25 +0300
Re: EMI problems Jeff Liebermann <jeffl@cruzio.com> - 2017-06-17 09:35 -0700
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-17 10:42 -0700
Re: EMI problems upsidedown@downunder.com - 2017-06-17 14:45 +0300
Re: EMI problems John Larkin <jjlarkin@highlandtechnology.com> - 2017-06-17 08:28 -0700
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