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321. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sat, 24 Sep 2011 14:04:39 -0700
The one of whom you speak reminds me of the observation that a certain guy had "a mind like a steel trap -- rusted shut." I long ago stopped wasting my time with folks like that. It's like arguing wi
/archives//html/Amps/2011-09/msg00172.html (9,679 bytes)

322. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sat, 24 Sep 2011 16:55:32 -0700
Common mode current results from imbalance at either end of the feedline. Most ham antennas are unbalanced to at least some extent by their surroundings -- trees, buildings, sloping earth, sloping an
/archives//html/Amps/2011-09/msg00175.html (9,422 bytes)

323. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sat, 24 Sep 2011 21:07:04 -0700
Ah, but it DOES, because the feedline is part of a complete circuit. If the rest of the circuit is unbalanced, it causes current in the feedline to be unbalanced. That's why I do not use the words "b
/archives//html/Amps/2011-09/msg00181.html (8,845 bytes)

324. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sun, 25 Sep 2011 00:10:47 -0700
Exactly. There is an excellent AES paper from 1994, published in the June 1995 Journal of the AES (Audio Engineering Society) by Bill Whitlock analyzing a balanced interface as a Wheatstone Bridge. T
/archives//html/Amps/2011-09/msg00188.html (10,803 bytes)

325. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sun, 25 Sep 2011 00:12:24 -0700
Yes, that's the rub. :) Jim _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
/archives//html/Amps/2011-09/msg00189.html (9,074 bytes)

326. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sun, 25 Sep 2011 00:51:59 -0700
It was a TEST -- i wanted to know the extent of heating by a differential field, which turned out to be small. I don't use open wire line. Not bad, but BETTER would be a string two-turn chokes throug
/archives//html/Amps/2011-09/msg00190.html (13,071 bytes)

327. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sun, 25 Sep 2011 00:55:19 -0700
I completely agree. When someone tells me they're using a G5RV (or a 43 ft vertical), I catalog them as "I'm a sucker who hasn't bothered to learn how antennas work, and fell for a good sales pitch."
/archives//html/Amps/2011-09/msg00191.html (8,109 bytes)

328. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sun, 25 Sep 2011 21:22:28 -0700
Not necessarily. See my measured data. YES! That's another reason for 5,000 ohms, and why more is better. As I said before, I don't have an application for OWL. All my antennas (about 15 at least cou
/archives//html/Amps/2011-09/msg00219.html (12,399 bytes)

329. Re: [Amps] RF in the Audio (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Mon, 26 Sep 2011 08:59:52 -0700
Paul, It isn't as simple as that. The ANTENNA is also part of the balance equation, and if the antenna is unbalanced, it will cause imbalance in the line. I summarized many common causes of antenna i
/archives//html/Amps/2011-09/msg00224.html (8,388 bytes)

330. Re: [Amps] Any QRO Ops wearing defibrilators (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sat, 19 Nov 2011 09:30:43 -0800
Hi Roger, I'm not an expert on the medical device side of this, but there are two fundamental concerns. First, is RF, and what matters is where your ANTENNAS are, not where your transmitter is. Frequ
/archives//html/Amps/2011-11/msg00082.html (7,987 bytes)

331. Re: [Amps] (no subject) (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Mon, 21 Nov 2011 14:30:14 -0800
Indeed, modern vehicles are NOT metal boxes, they are boxes of various plastics and metal, much of that metal painted, and often (mostly?) with no electrical contact between painted metal parts. This
/archives//html/Amps/2011-11/msg00101.html (9,911 bytes)

332. Re: [Amps] best deal for Mallory caps? (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Thu, 24 Nov 2011 09:17:14 -0800
Another important point. It's rare for all of the caps in the series string to fail. Only one gone bad will cause lots of hum. I use my trusty Simpson 260 on the middle Ohms range to read charge and
/archives//html/Amps/2011-11/msg00126.html (8,296 bytes)

333. Re: [Amps] best deal for Mallory caps? (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Thu, 24 Nov 2011 09:11:03 -0800
I think that's about what I paid about five years ago, and I bought at least a dozen. Don't recall if it was Newark or Allied, but I shopped them for price. 73, Jim K9YC _____________________________
/archives//html/Amps/2011-11/msg00128.html (7,966 bytes)

334. Re: [Amps] best deal for Mallory caps? (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Tue, 29 Nov 2011 09:35:07 -0800
Better than nothing my &$#@ It works VERY well to find a dead lytic in a string. Perhaps you have the bucks to spend on every possible piece of test gear, but most us have to make do with what we hav
/archives//html/Amps/2011-11/msg00172.html (8,243 bytes)

335. Re: [Amps] best deal for Mallory caps? (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sat, 03 Dec 2011 08:18:05 -0800
Exactly my point. And good ones will show a LOT. 73, Jim K9YC _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
/archives//html/Amps/2011-12/msg00022.html (7,368 bytes)

336. Re: [Amps] best deal for Mallory caps? (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sun, 04 Dec 2011 18:33:32 -0800
It would appear that your only purpose in life to try to make others look bad. The result is that you're making yourself look like one of our do-nothing congressmen! The original query was about a po
/archives//html/Amps/2011-12/msg00037.html (8,136 bytes)

337. Re: [Amps] Making RS-4XX interfaces RF resistant (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Thu, 22 Dec 2011 09:58:35 -0800
Two important measures. First, avoid Pin One Problems at both ends. Second, use twisted pair (CAT5/6/7 is a great choice) for each signal circuit. If the circuit is unbalanced, connect each signal re
/archives//html/Amps/2011-12/msg00194.html (9,304 bytes)

338. Re: [Amps] Fwd: Linear Amplifier Tuning---PROPERLY! (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Fri, 23 Dec 2011 19:04:42 -0800
IMD in the -30dB range means a LOT of RF trash in your sidebands, both from modulation and from the transients of your keying. That means you're TOO DAMNED BROAD! Keeping our signals as clean as poss
/archives//html/Amps/2011-12/msg00201.html (8,757 bytes)

339. Re: [Amps] Fwd: Linear Amplifier Tuning---PROPERLY! (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Sun, 25 Dec 2011 09:08:42 -0800
YES! And based on that lousy performance, the QST reviewer was FAR to kind to the product. 73, K9YC _______________________________________________ Amps mailing list Amps@contesting.com http://lists.
/archives//html/Amps/2011-12/msg00211.html (9,035 bytes)

340. Re: [Amps] IMD (score: 1)
Author: Jim Brown <jim@audiosystemsgroup.com>
Date: Fri, 30 Dec 2011 00:35:55 -0800
Me too. As has been noted by those who understand it, the fundamental causes are phase noise (from the exciter, amplified by the power amp) and IMD in both the exciter and the power amp. IMD (intermo
/archives//html/Amps/2011-12/msg00281.html (9,232 bytes)

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