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1. [RFI] Noisy PC Speakers (score: 1): Author: Tony <73guddx@gmail.com>; Date: Sat, 19 Sep 2020 00:10:05 -0400; All: Purchased a set of USB-powered PC speakers which turned out to be very noisy on HF. The speakers are made by Mica model PB20i. See: https://www.amazon.com/gp/product/B07VTS62L6/ref=ppx_yo_dt_b_a; /archives//html/RFI/2020-09/msg00050.html (7,066 bytes)
2. Re: [RFI] Noisy PC Speakers (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Fri, 18 Sep 2020 21:49:36 -0700; Hi Tony, Several years ago, W6GJB told me about his experience with a pair that powered off of USB. The DC-DC converter was the culprit. I would expect ANY device that powers from USB to have that so; /archives//html/RFI/2020-09/msg00051.html (7,882 bytes)
3. Re: [RFI] Noisy PC Speakers (score: 1): Author: Mike NA6MB <na6mb.mike@gmail.com>; Date: Fri, 18 Sep 2020 23:28:40 -0700; Great speakers ! http://www.westmountainradio.com/product_info.php?products_id=COM_spkr No RFI given and none taken. NA6MB Purchased a set of USB-powered PC speakers which turned out to be very noisy; /archives//html/RFI/2020-09/msg00052.html (7,613 bytes)
4. Re: [RFI] Noisy PC Speakers (score: 1): Author: Grant Saviers <grants2@pacbell.net>; Date: Sat, 19 Sep 2020 07:11:57 -0700; Plus they might use a class D amplifier which can be a great noise source. Grant KZ1W Several years ago, W6GJB told me about his experience with a pair that powered off of USB. The DC-DC converter wa; /archives//html/RFI/2020-09/msg00053.html (8,710 bytes)
5. Re: [RFI] Noisy PC Speakers (score: 1): Author: Tony <73guddx@gmail.com>; Date: Sat, 19 Sep 2020 18:28:13 -0400; Hi Jim: I would expect ANY device that powers from USB to have that sort of problem unless the designer has taken great care to avoid it. That does seem to be the case. I returned the speakers to Ama; /archives//html/RFI/2020-09/msg00054.html (9,382 bytes)
6. Re: [RFI] Noisy PC Speakers (score: 1): Author: Tony <73guddx@gmail.com>; Date: Sat, 19 Sep 2020 18:46:17 -0400; Thanks for the info Mike. I noticed that they give you the option of powering the speakers with the supplied AC adapter or the PC USB connection. Curious to know if you noticed any RFI when running t; /archives//html/RFI/2020-09/msg00055.html (8,570 bytes)
7. Re: [RFI] Noisy PC Speakers (score: 1): Author: Dave Cole <dave@nk7z.net>; Date: Sat, 19 Sep 2020 16:02:13 -0700; Ferrite up all leads into and out of the speakers... RFI will go away. 73, and thanks, Dave (NK7Z) https://www.nk7z.net ARRL Volunteer Examiner ARRL Technical Specialist, RFI ARRL Asst. Director, NW; /archives//html/RFI/2020-09/msg00056.html (9,970 bytes)
8. Re: [RFI] Noisy PC Speakers (score: 1): Author: David Eckhardt <davearea51a@gmail.com>; Date: Sat, 19 Sep 2020 23:04:58 +0000; Don't buy any speakers with active circuitry, especially digital. Active noise cancellation is a license for RFI. If it needs power other than the audio, beware! Dave - WØLEV -- *Dave - WØLEV* *Just; /archives//html/RFI/2020-09/msg00057.html (10,414 bytes)
9. Re: [RFI] Noisy PC Speakers (score: 1): Author: "Hare, Ed W1RFI" <w1rfi@arrl.org>; Date: Mon, 5 Oct 2020 15:59:10 +0000; The ARRL Lab received a report of interference from a Class D audio amplifier that had been installed about 500 feet from an amateur. We purchased a set of them, set them up in our C63.4 conducted-em; /archives//html/RFI/2020-10/msg00027.html (11,254 bytes)
10. Re: [RFI] Noisy PC Speakers (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Mon, 5 Oct 2020 10:48:47 -0700; On 10/5/2020 8:59 AM, Hare, Ed W1RFI wrote: We then hooked up 16 feet of wire and real speakers. Bingo! The noise level went up dramatically. It was my guess that the speaker leads were radiating, so; /archives//html/RFI/2020-10/msg00030.html (9,606 bytes)
11. Re: [RFI] Noisy PC Speakers (score: 1): Author: "Hare, Ed W1RFI" <w1rfi@arrl.org>; Date: Mon, 5 Oct 2020 18:00:48 +0000; < Second, every wire/cable connected to a noise source (in this case, the Class D amplifier, but also including switch-mode power supplies) forms a transmitting antenna for common mode current on tho; /archives//html/RFI/2020-10/msg00032.html (10,486 bytes)
12. Re: [RFI] Noisy PC Speakers (score: 1): Author: K9MA <k9ma@sdellington.us>; Date: Mon, 5 Oct 2020 13:52:11 -0500; Perhaps because the speaker wires were acting as a counterpoise, and actually increasing the conducted emissions on the power leads. Did you try a common mode filter on the power leads when the speak; /archives//html/RFI/2020-10/msg00033.html (8,295 bytes)
13. Re: [RFI] Noisy PC Speakers (score: 1): Author: "Hare, Ed W1RFI" <w1rfi@arrl.org>; Date: Mon, 5 Oct 2020 18:56:12 +0000; Well, I could have used the common-mode filter, which we'd do to solve an RFI issue, but it really was interesting to see the conducted noise increase due to the addition of length to the speaker wir; /archives//html/RFI/2020-10/msg00034.html (9,312 bytes)
14. Re: [RFI] Noisy PC Speakers (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Mon, 5 Oct 2020 13:50:09 -0700; That's probably because virtually all modern audio power amps are constant voltage devices -- VERY low output Z, typically 1/100 of the nominal load impedance. Up to the current limits of their power; /archives//html/RFI/2020-10/msg00035.html (9,484 bytes)
15. Re: [RFI] Noisy PC Speakers (score: 1): Author: "Hare, Ed W1RFI" <w1rfi@arrl.org>; Date: Tue, 6 Oct 2020 15:27:10 +0000; No, again, this was not a change in impedance, at least not much of one. We initially terminated the speaker outputs with 8 ohm resistors. We measured conducted emissions. We then put real speakers o; /archives//html/RFI/2020-10/msg00038.html (11,286 bytes)
16. Re: [RFI] Noisy PC Speakers (score: 1): Author: "Cianciolo, Paul, W1VLF" <pcianciolo@arrl.org>; Date: Tue, 6 Oct 2020 15:37:01 +0000; In addition to Ed's comments "twisting" the wire had little if any effect. Connecting one 1 of 2 speaker leads lead to a slight decrease in emissions. A single wire added to either of the speaker out; /archives//html/RFI/2020-10/msg00039.html (12,580 bytes)
17. Re: [RFI] Noisy PC Speakers (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Tue, 6 Oct 2020 09:42:45 -0700; Not surprising. Twisting primarily affects differential mode coupling. Audio power amps use a lot of feedback around the output stage, so any RF present on the speaker cable will be fed back and ampl; /archives//html/RFI/2020-10/msg00040.html (10,862 bytes)
18. Re: [RFI] Noisy PC Speakers (score: 1): Author: David Eckhardt <davearea51a@gmail.com>; Date: Tue, 6 Oct 2020 17:41:05 +0000; When there is a radiated or conducted problem with a piece of equipment, there are two VERY GENERAL methods to reduce problematic emissions: A) Reduce the level of emission at the source (source supp; /archives//html/RFI/2020-10/msg00041.html (12,888 bytes)

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