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341. Re: [RFI] Fair Rite #31 Mix Material (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 12 Jan 2009 00:45:25 -0800
Before you place too much confidence in data from your network analyzer, study my measurement travails, documented in the Coaxial Chokes Power Point. Ferrite chokes are VERY difficult to measure accu
/archives//html/RFI/2009-01/msg00085.html (10,506 bytes)

342. Re: [RFI] Fair Rite #31 Mix Material (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 12 Jan 2009 09:39:28 -0800
Yes. With ferrites, the primary effect is to shift the resonance down in frequency. Because the capacitance of the DUT is so small, a rather small value of stray C is not insignificant. My estimate o
/archives//html/RFI/2009-01/msg00090.html (10,075 bytes)

343. Re: [RFI] Hum in Bose QC2 headphones (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 13 Jan 2009 20:21:09 -0800
If what you hear is HUM (pure 60 Hz) rather than BUZZ (little or no 60 Hz, but lots of 180, 360, 420, etc.) suspect a magnetic field coupling problem. If what you hear is BUZZ, suspect power-related
/archives//html/RFI/2009-01/msg00096.html (7,398 bytes)

344. Re: [RFI] Hum in Bose QC2 headphones (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 13 Jan 2009 21:54:11 -0800
You may have a magnetic field problem due to wiring errors in your AC power distro. There must be ONE, BUT ONLY ONE, bond between neutral and ground in any power system, and that bond must be at the
/archives//html/RFI/2009-01/msg00102.html (8,577 bytes)

345. Re: [RFI] Hum in Bose QC2 headphones (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Thu, 15 Jan 2009 10:31:16 -0800
As I observed much earlier in the thread, this problem has the symptoms of magnetic field coupling because Gary has described it as pure 60 Hz hum, NOT BUZZ. If power system wiring is correct, the ma
/archives//html/RFI/2009-01/msg00120.html (10,691 bytes)

346. [RFI] RFI Susceptibility of DTV? (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Wed, 21 Jan 2009 23:32:45 -0800
Can anyone point me to engineering references that discuss the relative susceptibility to RFI of DTV as compared to analog TV? That is, is DTV more or less susceptible to interference, or about the s
/archives//html/RFI/2009-01/msg00158.html (6,565 bytes)

347. Re: [RFI] RFI Susceptibility of DTV? (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 23 Jan 2009 15:18:33 -0800
That's in conflict with what I'm seeing. One piece of info that came to me in response to my initial question was a report showing DTV to be quite susceptible to interference from impulse noise and d
/archives//html/RFI/2009-01/msg00169.html (11,005 bytes)

348. Re: [RFI] RFI Susceptibility of DTV? (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 23 Jan 2009 19:12:19 -0800
Depends on what you call useful. antennaweb got my address right on a map, and told me there were NO signals at my QTH. My local TV comes from two sites, one 42 miles away and the other 45 miles, onl
/archives//html/RFI/2009-01/msg00176.html (11,136 bytes)

349. Re: [RFI] 2nd harmonic help (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Tue, 03 Feb 2009 19:58:41 -0800
What are you using for antennas? How much separation? What kind of feedlines? It's not at all surprising that you're having trouble with harmonics. Filters don't reduce out of band signals to nothing
/archives//html/RFI/2009-02/msg00030.html (8,273 bytes)

350. Re: [RFI] VLF interference Re: CFLs and LEDs (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sat, 07 Feb 2009 11:27:26 -0800
Yes. I've had at least a dozen CFLs in my home for about two years. No issues, no RFI. Most came from Costco, a few from a local hardware store. My electricity bill is a lot lower as a result, and sl
/archives//html/RFI/2009-02/msg00045.html (9,696 bytes)

351. Re: [RFI] 80/160M RFI in neighbor's oven circuitry ! (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 08 Feb 2009 00:36:01 -0800
I had this sort of problem when I lived in Chicago with a very old microwave. Fixed it with a capacitor across the AC line. Don't remember whether it was line to neutral or line to ground. Think it w
/archives//html/RFI/2009-02/msg00061.html (7,953 bytes)

352. Re: [RFI] 80/160M RFI in neighbor's oven circuitry (PART 2) (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 08 Feb 2009 09:24:26 -0800
And a complete waste of time. The earth is NOT a sink into which noise and RF is poured. You've described a microwave that is permanently installed. Many microwaves are not -- they simply plug into a
/archives//html/RFI/2009-02/msg00069.html (8,538 bytes)

353. Re: [RFI] 80/160M RFI in neighbor's oven circuitry (PART 2) (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 08 Feb 2009 21:48:30 -0800
Dave, A filter is essentially a frequency-sensitive voltage divider, so the bottom of the voltage divider has to be connected to SOMETHING to "work worth a damn." The bottom of the voltage divider is
/archives//html/RFI/2009-02/msg00074.html (9,322 bytes)

354. Re: [RFI] Alternative Power Source Questions (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Mon, 09 Feb 2009 23:11:16 -0800
Yes, they can be very nasty noise sources. The fundamental problem is that the charging currents are pulse regulated, and the circuit designer has ignored fundamental design rules to prevent RFI. The
/archives//html/RFI/2009-02/msg00082.html (8,197 bytes)

355. Re: [RFI] Zoom X6 DSL Modem loses internet connection (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 13 Feb 2009 09:38:29 -0800
You should also call your DSL vendor and tell them that their modem has RFI problems, and ask THEM to fix it. It IS their problem, not yours. W8JI had issues with his modem, and got a replacement tha
/archives//html/RFI/2009-02/msg00091.html (7,907 bytes)

356. Re: [RFI] DSL interference (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Thu, 19 Feb 2009 09:24:59 -0800
Hi Bud, Exactly which #31's are applied and exactly how are they applied to which cables? 73, Jim K9YC _______________________________________________ RFI mailing list RFI@contesting.com http://lists
/archives//html/RFI/2009-02/msg00099.html (6,823 bytes)

357. Re: [RFI] Current balun construction? (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 22 Feb 2009 11:21:02 -0800
The only thing that's slick is the guy who sold it to you for five times what it cost him. It's a LOUSY excuse for a common mode choke. Yes, it IS the fault of the so-called balun. Study http://audio
/archives//html/RFI/2009-02/msg00107.html (7,734 bytes)

358. Re: [RFI] Computer Speaker RFI (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 01 Mar 2009 10:16:47 -0800
Turn them off. :) But seriously -- I assume you're talking about speakers with built-in power amplifiers, either battery-operated or AC powered. The electronics built into powered loudspeakers are no
/archives//html/RFI/2009-03/msg00001.html (8,142 bytes)

359. [RFI] K-Com Filters (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 01 Mar 2009 10:34:38 -0800
I'm currently writing the EMC chapter for the 2010 ARRL Handbook, and wanted to be sure to include info on good products like K-Com telephone filters. The webpage is down, so I tracked down Mr. K-Com
/archives//html/RFI/2009-03/msg00002.html (7,168 bytes)

360. Re: [RFI] Computer Speaker RFI (score: 1)
Author: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Sun, 01 Mar 2009 11:17:06 -0800
Joe, There's a fair chance that a serious multi-turn ferrite choke could fix this problem. Something like 8 turns around a #43 or #31 toroid on each cable that enters the sub-woofer. AND -- if this i
/archives//html/RFI/2009-03/msg00003.html (7,715 bytes)

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