My calculations assume that the LED lamp conducted emissions are at the FCC
limit at a single frequency in the 160 meter band. This is not real world.
I'll buy a lamp and characterize the conducted emissions.
Dave WX7G
On Apr 6, 2012 4:44 PM, "DAVID CUTHBERT" <telegrapher9@gmail.com> wrote:
> ---------- Forwarded message ----------
> From: "DAVID CUTHBERT" <telegrapher9@gmail.com>
> Date: Apr 6, 2012 4:42 PM
> Subject: Re: Topband: Home Depot LED bulb interference.
> To: "GeorgeWallner" <aa7jv@atlanticbb.net>
>
> LED lamps no doubt comply with FCC conducted emissions. The noise is almost
> entirely differential mode. Think of a signal on an open wire t-line; it
> does not radiate (much).
>
> But, the asymmetry in the AC power system causes differential to
> common-mode conversion. Common-mode current on an open wire feedline
> radiates (a lot).
>
> The primary asymmetry I see is the neutral wire to earth ground. I ran a
> NEC sim of a simplified house AC power with feed wires to a power pole. The
> signal induced into a 160 meter dipole next door is S-8 from a single LED
> lamp at the FCC limit of 2 mV differential into 100 ohms.
>
> Disconnecting the AC earth ground wire drops the signal by 40 dB. Ferrites
> clamped onto the earth ground wire could help.
>
> This is crude and preliminary but is interesting as I'm an EMC design
> engineer as well as a ham.
>
> Dave WX7G
> On Apr 6, 2012 4:22 PM, "GeorgeWallner" <aa7jv@atlanticbb.net> wrote:
>
> > On Fri, 6 Apr 2012 11:57:15 -0700 (PDT)
> > "Jim F." <j_fitton@yahoo.com> wrote:
> > ...Since this bulb complies with
> > > part 15 of FCC rules
> >
> > It is marked to comply, but it may not. (Part 15
> > compliance is self-certified. It would be interesting to
> > test it against Part 15 requirements.
> >
> > I believe that one of our potential defences against the
> > worst offenders is to bring the attention of retailers to
> > the pontial risks of selling non FCC comliant products.
> > The more cautious they get the better off we will be.
> > Returning it to the retailer is a good start in that
> > direction!
> >
> > George
> > _______________________________________________
> > UR RST IS ... ... ..9 QSB QSB - hw? BK
> >
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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