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Old 21st December 2002, 12:47 PM   #1
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Default NOISE - RFI and EMI

I snip the following from this morning's (21 Dec 02) ARRL Member e-newsletter as it has ramifications for DIY-audiophiles:<p><em>
* League keeps eye on emerging RFI issues: ARRL Lab Supervisor Ed Hare,
W1RFI, attended a November 12-14 meeting of the IEEE C63 "RFI" committee
in Baltimore. Hare's visit was in response to a committee invitation for a
presentation on the possible impact of Power Line Communications (PLC) on
Amateur Radio. Hare also attended a very high bit-rate digital subscriber
line (VDSL) standards meeting in Atlanta November 18-19. Hare says that
both technologies present a potential to radiate signals that could raise
the noise floor on nearby HF receivers by tens of dB. "What ham hasn't
looked up at a power line and thought, 'Now there's a heck of a longwire
antenna!'" Hare quipped. "The problem with PLC is that if a company wants
to supply Internet service via PLC, it's going to happen at HF, and it
will radiate." Following the presentation, the IEEE named Hare chairs its
ad hoc working group on PLC. VDSL presents somewhat less of a challenge
than PLC, Hare said, but for overhead telephone wiring, it's important
that the industry include protections for Amateur Radio. Hare said the
ARRL will continue to work these and other industry groups and build on
the successes Amateur Radio has had recently with the HomePlug group and
Home Phoneline Network Alliance in reducing interference to amateur HF
bands.
</em>
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Old 21st December 2002, 04:02 PM   #2
dhaen is offline dhaen  Europe
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Yes, the noise floor keeps on rising.
Balanced interconnects, essential in professional installations, may yet become the order if the day, in quality domestic installatons.

Also, those using phase correction caps in their feedback loops, may like to consider what is being fed back to the input stage from pickup by the speaker cables.

We're all doomed..
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Old 21st December 2002, 04:20 PM   #3
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Quote:
Originally posted by dhaen
Also, those using phase correction caps in their feedback loops, may like to consider what is being fed back to the input stage from pickup by the speaker cables.
That's why Rod Elliot suggests using a Zobel filter on the output
also on preamps, and by the same reasoning one should
probably use it also in the CD player etc.
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Old 21st December 2002, 04:32 PM   #4
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Quote:
Originally posted by dhaen
Yes, the noise floor keeps on rising.
Balanced interconnects, essential in professional installations, may yet become the order if the day, in quality domestic installatons.
Two houses back, they put a cellphone installation on the roof of the building next to me, maybe 15m from where I slept and where my system was. The day they first power it up for tests, I heard the noise level in my system go up a LOT, even though it was never quiet due to an inner city location.

I moved, because I didn't want to be irradiated constantly, but now I live in the country, my system mains and RF issues are a thing of the past.

Cheers
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Old 21st December 2002, 08:49 PM   #5
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While we are talking about line noise, there has been a
dramatic increase in line wave distortion in the past few years
so that transformers which were formerly quiet now buzz
like hell. Manufacturers are continually having to upgrade
their transformers and create filter networks to deal with it.

Also, many countries world wide have adopted tough
emissions standards for consumer products as a thinly
disguised trade barrier, while continuing to import goods
into the US which do not meet these standards because
the US has very lax requirements.

This means that all the little companies are having trouble
selling electronics into these countries because of the testing
and paperwork which is very expensive and time consuming.
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Old 21st December 2002, 09:02 PM   #6
dhaen is offline dhaen  Europe
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Quote:
Also, many countries world wide have adopted tough emissions standards for consumer products as a thinly
Nelson,
If you're referring to CE marking in Europe; I assure you it's a nightmare for little companies here too
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Old 21st December 2002, 10:17 PM   #7
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Default RFI/EMI

Hi,

Maybe time to open up the book on how to best tackle these problems from an audio angle?

Ciao,
__________________
Frank
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Old 21st December 2002, 10:21 PM   #8
dhaen is offline dhaen  Europe
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Default Which problems?

The thread has drifted somewhat
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Old 21st December 2002, 10:24 PM   #9
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Default Nelson - you mean those phones from China?

these are real QRM creators. They don't even bother to pay lip service to FCC regs.

If you hear a buzzing transformer or line, complain to the utility right away AND copy the letter to the local FCC office. You can really hot-foot this stuff by raising a stink. Generally the utilities are at fault. Oftentimes it's loose connections, but frequently a faulty transformer etc.
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Old 26th February 2005, 01:01 PM   #10
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Default Why is my stereo clicking?

The FCC recently entered into a consent decree with an importer of electric blankets:

==>ARRL HOPES CONSENT DECREE WILL REDUCE INTERFERENCE COMPLAINTS

The FCC has agreed to terminate enforcement action against an importer and
marketer of heated mattress pads and blankets--and associated external
switching power supplies--in exchange for the company's signature on a
Consent Decree. The case involved numerous interference complaints from
Amateur Radio operators and others related to consumer products marketed by
Perfect Fit Industries (PFI) of Charlotte, North Carolina.

"The Enforcement Bureau and PFI have negotiated the terms of a Consent
Decree that would resolve this matter and terminate the investigation," the
FCC announced in releasing an Order in the proceeding February 10. The Order
includes a copy of the Consent Decree. PFI also will make a "voluntary
contribution" of $7000 to the US treasury.

ARRL Laboratory Electromagnetic Compatibility Engineer Mike Gruber, W1MG,
said the League has been receiving an increasing number of reports from
radio amateurs about interference from modern switching-type power supplies.
Ironically, one complaint came from Gruber's boss--ARRL Lab Manager Ed Hare,
W1RFI, whose wife had purchased one of the blankets. Hare says a further
irony involves the FCC's reaction in this case to an apparent Part 15
emissions violation.

"It's paradoxical that an electric blanket marketer is getting this level of
FCC attention for a conducted emission that's less than 1 percent of the
power level BPL manufacturers have told the FCC they use in their
installations," he commented.

The ARRL Lab examined one of the offending blankets, which emitted a ticking
sound even while turned off but still plugged into the ac outlet. Gruber
noted that many products of this type appear to be made overseas and do not
carry the required labeling described in Part 15 of the FCC's rules. Owing
to negligence or ignorance of the FCC requirements for conducted and
radiated emissions limits, he says, some of these devices may operate at
levels significantly higher than the rules permit.

"We hope this case will serve as a reminder to other manufacturers that
their switching supplies need to be tested for compliance with the rules and
carry the proper labeling as required by Part 15," Gruber said. But, he
added, FCC's Part 15 limits are not a cure-all for interference--an
assertion borne out in other cases involving interference from unlicensed
devices such as broadband over power line (BPL) interference or common power
line noise.

"On the contrary, the limits are set high enough that interference--as was
seen in cases involving these products--is likely," he pointed out. "Part 15
requires that operators of unlicensed devices that cause harmful
interference must take whatever steps are necessary to correct the
interference or cease operation whenever interference occurs."

As part of the Consent Decree, PFI will put into place an FCC "Regulatory
Compliance Plan" with an eye toward ensuring future compliance. Among other
things, the company will have to designate a compliance officer to
administer the plan. PFI further agreed to replace free of charge any
noncompliant mattress pad or heated blanket with a compliant product upon
receipt of an interference complaint.

In addition, PFI will agree that its electric mattress pads and blankets and
associated external switching power supplies will comply with FCC Part 2 and
Part 15 rules before they're imported and marketed. The Consent Decree is
good for three years.

Signing the Consent Decree for the FCC was Enforcement Bureau Chief David H.
Solomon. PFI President and CEO Louis R. Morris signed on the company's
behalf.

Sound recordings of the electric blanket and mattress pad RFI are available
on the RF Noise Identification Web site
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