Thanks for relating, Ed. And you (et.al) should wonder why I see a crying
need to revisit limits, measurement philosophies, and even C63.4. But it
won't happen in my lifetime as I just turned 76 (pray for a flip of the
magnetic poles of the earth????).
I've always tested to "as typically installed or used by the consumer". We
all know resistors are (ideally) non-reactive and convert electric energy
to heat (and some infrared electromagnetic radiation, but that's for the
safety guys). Not so with speaker "antenna" wires.
And the real problem with solar power is how do you satisfy that
requirement in a typical 10-meter Semi Anechoic Chamber? With all the
connecting wiring, it doesn't fit on the turntable. Man, I still favor
OATS in a nice quiet valley in the Rockies. We used to have just such an
installation, but the guy lost his accreditation due to not keeping up with
the paperwork.
Dave - WØLEV
On Sun, Dec 25, 2022 at 9:14 PM Hare, Ed, W1RFI <w1rfi@arrl.org> wrote:
> The one i have experience was a Class D amp intended to be wall mounted
> and connected to with bluetooth. A ham with a very sensitive setup was
> hearing it 1700 feet away. Yikes!
>
> Now, here's the interesting story that I need to find time to document so
> I can present it at a future IEEE EMC Symposium, or at least publish it as
> a peer-reviewed article. It really points out a problem that could impact
> future standardization.
>
> So, I bought one of the Class D amps in question. I terminated its speaker
> outputs in 15 ohms and I tested its conducted emissions in "standby" and
> powered on. It measured about 10 dB below the Part 15 Class B limits. What
> the actual heck is going on? There is no way the conducted emissions could
> be heard that far away, so I explored farther. I connected a signal
> generator to it and cranked it up. Conducted emissions increased slightly,
> but not to the point where I believed this to be the radiated problem.
>
> So, I assumed that the speaker leads were the radiators, so I took off the
> 8-ohm resistors and put them at the end of 16-foot speaker wires, zip type,
> untwisted, to be a reasonable worst case. I brought out the EMCO loop
> antenna and put it about 10 meters away. (Yes, this was in the Lab, so
> scatterers galore, but I was looking for gross problems. Yup, it was
> loud. So I then put an L/C filter in the speaker lead and a ferrrite
> choke. It was STILL pretty loud. I then happened to look at the conducted
> emissions. The CONDUCTED emissions were about 20 dB or more higher.
>
> It turns out that the coupling from the common-mode currents put on the
> speaker leads to nearby conductors unbalanced the conducted emissions,
> creating a substantial common-mode current that changed conducted
> emissions. So, when tested in a Lab with 8-ohm resistive terminations on
> the speaker lead, the unit "passed," but when used in its normal fashion,
> with real speakers, it did not.
>
> I had remembered years back we were testing an LED bulb that just passed
> Part 15B, when I went to unscrew it, the conducted emissions rose quite a
> bit. Well, I knew that there is no way FCC would consider that to be
> actionable, so I forgot about it and did the rest of my tests. But the
> incident with the Class D amp piqued my curiousity, so i got out some
> spotlight LED bulbs that were near the limit and tested them again. Sure
> enough, putting my hand near them caused conducted emissions to rise.
> Interesting, but still not actionable.
>
> My test fixture was a simple ceramic socket, placed in a C63.4 compliant
> room. I then purchased on of the "cans" that most spotlight bulbs are
> installed in, and grounded it to the room ground plane. The conducted
> emissions increased by 8 dB simply by using the bulb in a way that it is
> very likely to be used. To me, this speaks loudly to the need to make
> revisions to the test standards, which simply measure the bulb pretty much
> the way I did.
>
> There is plenty of work to keep me busy for the rest of my life! 🙂
>
> Ed Hare, W1RFI
> ARRL Lab
>
>
>
>
>
> ------------------------------
> *From:* RFI <rfi-bounces+w1rfi=arrl.org@contesting.com> on behalf of
> David Eckhardt <davearea51a@gmail.com>
> *Sent:* Sunday, December 25, 2022 3:22 PM
> *To:* Henry Pfizenmayer <pfizenmayer@q.com>
> *Cc:* rfi@contesting.com <rfi@contesting.com>
> *Subject:* Re: [RFI] : Solar Panerl RFI / noise in sync with music
>
> It likely was a Class-E amp (or worse). They can be dirty as $%^& when
> stressed (by the strong bass notes).
>
> I once tested a Class-E home automation system with all kinds of Class-E
> amps (for intercoms and distribution of music from a number of sources).
> It was the ONLY product in 35+ years we had to install an 20 dB attenuator
> in series with the input to the R&S conducted emissions receiver!
>
> Dave - WØLEV
>
> On Sun, Dec 25, 2022 at 8:09 PM Henry Pfizenmayer via RFI <
> rfi@contesting.com> wrote:
>
> > Mike et al ---If that was not tongue in cheek as they say -- this last
> > summer I started getting thumps of
> >
> > noise on 6 meters -and was far worse at 25 mhz -- Then I noticed it was
> > in sync with neighbors outside
> >
> > speakers thumping out a strong bass line. I went out with my IcomR10
> rx
> > and loop -
> > and yep that was the source. The amp was obviously going into oscillation
> > in sync with the loud bass notes .
> > No use talking to that guy - so I just prayed the damn amp would fry
> > itself . Prayers were answered
> >
> > in just a hour or so and noise never re-appeared.
> >
> >
> >
> > 73 Hank K7HP
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Message: 1
> > Date: Sun, 25 Dec 2022 11:51:20 -0500
> > From: Michael Martin <mike@rfiservices.com>
> > To: "Dave (NK7Z)" <dave@nk7z.net>
> > Cc: Rfi List <rfi@contesting.com>
> > Subject: Re: [RFI] Another Solar Panel RFI System
> > Message-ID:
> > <CAPZkRSEvyTNyLcJT-3e1gNnkTP+WNX15DFXUXHpqf5YZa67YEw@mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > I'm trying to capture a noise with the intermittency rhythm in sync with
> > Christmas music
> >
> > Michael Martin
> > RFI Services
> > 51 W Bay Front Rd
> > Lothian, MD 20711
> >
> > 240-508-3760
> > mike@rfiservices.com
> > [http://www.rfiservices.com<]www.rfiservices.com<
> > https://webmail.centurylink.net/app/www.rfiservices.com>
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
> >
>
>
> --
> *Dave - WØLEV*
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
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>
--
*Dave - WØLEV*
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