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Re: KPA 500 Hum PC Speakers.

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Bill K9YEQ

Re: KPA 500 Hum PC Speakers.

Note the changed subject. Computer speakers are cheaply made, no shielding.
If you are lucky won't have issues. In your cases, suggest moving them away
from equipment. Don't forget that stray rf loves audio as well. Grounding,
antenna location, etc. can all play a role. (I have no hum while
transmitting. I did add an isolator between the K3 and amplified PC
Speakers.)

73,
Bill
K9YEQ

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Monday, August 01, 2011 2:14 PM
To: [hidden email]
Subject: Re: [Elecraft] KPA 500 Hum

Klaus,

Are you sure it is the KPA500?

My computer speakers in the shack will hum when using any of my HF
amplifiers on CW.

73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

On Mon, 1 Aug 2011 07:33:05 +0000, Klaus Koppendorfer <[hidden email]> wrote:

>
>Last week i assembled the kpa500 of oe6rdd when we transmit we hear a
>realy loud hum (50hz) in the rythm of the cw signals
>
>i have compared this with my own kpa-500 and there is no hum i have
>tried to loosen the big srew which holds the tranformer with no result
>
>any ideas ??
>

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Ken G Kopp

RF in PC Speakers.

I have a pair of West Mountain Radio COMspkrs
that are interference-free. Took awhile to get 'em,
as they were on back order for "too long".

The side of the unit with the amplifier is literally
touching the side of a THP KW amplifier and the
other speaker is about 12" from my open wire
feeders.

FWIW, your MMV ...

73!
Ken - K0PP
[hidden email]

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Tim Tucker

Re: RF in PC Speakers.

I have the same speakers and am very happy with them. The best part is the
powered volume control which I desired because I wan't some more volume from
the K3.

On Mon, Aug 1, 2011 at 9:38 PM, Ken - K0PP <[hidden email]> wrote:

>
> I have a pair of West Mountain Radio COMspkrs
> that are interference-free. Took awhile to get 'em,
> as they were on back order for "too long".
>
> The side of the unit with the amplifier is literally
> touching the side of a THP KW amplifier and the
> other speaker is about 12" from my open wire
> feeders.
>
> FWIW, your MMV ...
>
> 73!
> Ken - K0PP
> [hidden email]
>
>
> ______________________________________________________________
> Elecraft mailing list
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ke9uw

Re: KPA 500 Hum PC Speakers.

In reply to this post by Bill K9YEQ

The hum is due to magnetic field in close proximity of the speaker...usually. Sometimes RF gets into them usually on the power cord. Ferrite fixes this, moving the speakers fixes the former.
Chuck, KE9UW

Chuck, KE9UW

Joe Subich, W4TV-4

Re: KPA 500 Hum PC Speakers.

RFI problems with the computer speakers are generally due to the
absence of the bypass components recommended by the amplifier chip
designers. I have seen several inexpensive computer speakers with
holes for the bypass caps on the circuit board (the chip maker's
reference design) but no parts. Generally, all it takes to make
the speakers "bullet proof" is adding the missing parts. In the
worst cases adding a couple molded 100 uH or 1 mH chokes in series
with the speaker lines inside the "amplifier" case resolved the
remaining RFI problems.

73,

... Joe, W4TV

On 8/2/2011 11:57 AM, ke9uw wrote:

> The hum is due to magnetic field in close proximity of the speaker...usually.
> Sometimes RF gets into them usually on the power cord. Ferrite fixes this,
> moving the speakers fixes the former.
> Chuck, KE9UW
>
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