A Google Search using "Pin 1 Computer Speakers" brings up
a hit that leads you to this mail from K9YC which led to the 1 article
link I just forwarded
73, Dennis N6KI
K9YC wrote:
*Study the Ferrites and RFI tutorial on my website, especially the
Power Point that includes material about "the pin 1 problem." The
latter is a major cause of RFI, and virtually ALL computer audio
gear (and nearly all ham gear) is built with pin 1 problems. In
general, "computer speakers" are pretty close to the bottom of the
barrel. They will have pin 1 problems, and they will likely be
completely unshielded. In fact, nearly all powered professional
speakers are also unshielded -- I can light them up with a 5W VHF
talkie at 5 ft.
Also see the discussion in the Ferrite tutorial about what I call
"threshold effect."
There are several other RFI papers there that should be helpful.
http://audiosystemsgroup.com/publish
I'd bet that >90% of the problem is input/output wiring acting as
antennas and pin 1 problems letting it in the door.
73,
Jim Brown K9YC
*
On Mon, Oct 20, 2008 at 12:41 PM, Dennis Vernacchia <n6ki73@gmail.com>wrote:
> Doug,
>
> The answer may be here in K9YCs article
>
> http://audiosystemsgroup.com/Pin_1_Revisited.pdf
>
> Let us know if you are successful resolving teh matter and how
> you de RFI'd teh system
>
>
> 73, Dennis N6KI
> Sandy Eggo
>
>
> On Mon, Oct 20, 2008 at 12:35 PM, Doug Grant <dougk1dg@gmail.com> wrote:
>
>> My wife recently bought a new PC. The (conventional analog) speakers
>> that came with it were defective, and when we returned them, the shop
>> was out of stock, but offered to give us a pair of HP-branded
>> USB-powered speakers at no charge.
>>
>> They work fine.
>>
>> However, they also appear to be the source of some really ugly RFI
>> that I hear on 160 and 80M. Even with the PC powered off, it appears
>> that the USB port still delivers power. With the PC off, and the
>> switch on the speakers turned OFF, there's no noise. If I turn the
>> power switch on the speakers ON, a broad 20-kHz-wide (+/-) signal
>> appears, spaced every 150 kHz or so, and drifiting around slowly. A
>> quick test of a clamp-on ferrite on the USB cable, then wrapping 10 or
>> so turns of the cable around a bigger toroid did not make a dent in
>> it.
>>
>> Not sure if it is noise on the USB power or if the speakers have
>> poorly-decoupled Class-D amplifiers in them causing the noise.
>>
>> I am sharing this so that anyone with a similar noise problem might
>> benefit, and also to see if anyone has encountered this problem, and
>> has a better solution than mine (which is to ask my wife nicely to
>> turn off the PC speakers when I am on the low bands).
>>
>> Does anyone make a USB filter that cleans up the power line without
>> compromising the data lines?
>>
>> 73,
>>
>> Doug K1DG
>> _______________________________________________
>> RFI mailing list
>> RFI@contesting.com
>> http://lists.contesting.com/mailman/listinfo/rfi
>>
>
>
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