The first time I got on the air on 20 meters after purchasing and hooking up
my brand new subwoofer to our home entertainment system, I really heard a
racket from the subwoofer...even though the entertainments systems amp was
off.
The sub does not have an on/off switch and uses signals from the
entertainment system to turn itself on and off...hence audio signals, which
I surmise are a form of "rf".
I had to get inside and install ferrite clamp on chokes on the sub woofer
speaker leads from the subwoofer amp (which did not affect the normal sound
quality at all) to the speaker, on the subwoofer power supply to the sub amp
as well as both the a/c cord and the dc leads going from the subwoofer power
supply to the subs amp.
It all helped quite a bit.
----- Original Message -----
From: "Duane A Calvin" <ac5aa@juno.com>
To: <tentec@contesting.com>
Sent: Wednesday, August 11, 2004 2:45 PM
Subject: Re: [TenTec] Argo RF In to computer Speakers..
> Ah, so, it might be true. Yes, this is a powered subwoofer, which most
> of the PC subwoofers are. In my case, it is the electronics inside the
> box that is susceptible because the case has no shielding, it's
> definitely in an RF-rich environment, and adding cores to all the wires
> has had no effect at all. My cores are the correct mix for 14 MHz
> signals and work well in other applications in the station. Of course, I
> could go in and redesign the amplifier, lowpass and bypass it. Or, I
> could reach over and turn the volume down and live with it. I was merely
> pointing out that adding cores to the wires may be a solution, or it may
> not - it depends on where the problem is occurring. I wasn't challenging
> the advice being given, merely adding to it.
>
> 73, Duane
>
>
> On Wed, 11 Aug 2004 15:19:07 -0500 "Jim Brown"
> <jim@audiosystemsgroup.com> writes:
> > On Wed, 11 Aug 2004 11:58:30 -0500, Duane A Calvin wrote:
> >
> > >And, there are some speakers that cannot be cured with ferrites
> > because
> > >the reception is actually happening inside the speaker.
> >
> > That might be true, but it also might not.
> >
> > First, passive loudspeakers do NOT detect RF. If the loudspeaker has
> > an
> > internal power amp, that power amp CAN detect the RF.
> >
> > Second, you may have not used the "right" ferrite, or you may have
> > used too
> > few, or even too many, turns.
> >
> > Third, the RF could, as you say, be picked up on wiring internal to
> > the power
> > amplifier due to its poor shielding. In my experience, that is the
> > least common
> > and least powerful mechanism. The more common one is antenna action
> > on
> > either the power leads or the signal wiring. In those instances,
> > choking the
> > current will generally eliminate the RFI.
> >
> > Jim Brown K9YC
> >
> >
> > _______________________________________________
> > TenTec mailing list
> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
> >
>
>
> Duane Calvin, AC5AA
> Austin, Texas
> _______________________________________________
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> TenTec@contesting.com
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>
>
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