>> The new 12 volt 'artsy' lighting systems can do exactly this.
>> These systems utilize high current switchers to convert line
>> to 12V (very high current). The lighting is strung using open
>> copper wire (great antennas) throughout the room or house. It
>> is the current cutting edge in home lighting and very noisy
>> at RF as the switchers sacrifice a lot for switching
>> efficiency and high current capability.
>> We have one in my 'hood which has taken N0CD off of 160m and
>> which I can hear even though I am several miles away
>> from the source. The household involved has been somewhat
>> cooperative, and the manufacturer has shipped new supplies,
>> but it is not any better. One of the big problems with these
>> systems is that they generate such high DC currents that
>> gettting any significant inductance on the wires is going to
>> take a very large amount of ferrite material.
> Suggest you or he contact Ed Hare (W1RFI@ARRL.ORG) and look at the
> information on FCC Part 15 Rules to be found on the ARRL's
> Web site in the TIS section. Ed may already be working on this problem
with the
> manufacturers, and in any case can give you good advice.
See http://www.arrl.org/tis/info/part15.html for a description of applicable
Part 15 rules.
See http://www.arrl.org/tis/info/rfi-elec.html for an article on electrical
interference (although it is very much slanted toward power lines).
This device is classified as an unintentional emitter under Part 15 rules.
There are no specific limits, but the regulations have a vague requirement
that manufacturers use good engineering practice.
§ 15.13--Incidental radiators--states that "Manufacturers of these
devices shall employ good engineering practices to minimize the risk
of harmful interference."
I will add a bit of info. It is not the "open" copper wires that usually do
the radiating; if they are spaced close together, they will still be
transmission lines and not radiate much. But these devices are probably also
putting RF hash back onto the house electrical wiring. Under some
circumstances, house electrical wiring is a transmission line, too, albeit
one that is unbalanced because the neutral wire is grounded at the service
entrance or service panel. But the minute one does the simple act of
opening a light switch, the balance is gone -- that open switch disconnects
the hot wire, but leaves the neutral wire connected -- a single wire
"antenna" is now connected to the line. EZNEC models have predicted that
this is a good antenna. Even a few milliwatts can be heard for a
considerable distance.
In most cases, switching mode power supplies generate a differential-mode
signal that is coupled onto the power lines. An unfiltered switcher will
probably put has on its input and output sides. Little of this noise will
be common mode, so a common-mode choke will probably do little good; this
type of noise is taken care of with "brute-force" type filtering.
If one of these devices can be heard for miles, IMHO, this is very clearly
NOT good engineering practice; that sounds like one WHOPPING signal from a
Part 15 device.
Please send me info about the device and any manufacturer information you
have and I will see if I can get some dialogue going with their engineering
staff. If these things become widespread, ham radio will certainly suffer.
I can run to Home Depot and buy a 12-volt lighting system, but before I
contact that manufacturer, I would have to do some testing. I can contact
the manufacturer whose device can be heard for miles based on a report
alone.
73 from ARRL HQ,
Ed Hare, W1RFI
ARRL Lab
225 Main St
Newington, CT 06111
860-594-0318
w1rfi@arrl.org
--------------------------------------------------------------------
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--------------------------------------------------------------------
> -----Original Message-----
> From: Pete Smith [mailto:n4zr@contesting.com]
> Sent: Thursday, December 02, 1999 9:56 AM
> To: rfi@contesting.com
> Subject: RE: [RFI] Mystery buzz 1.7 to 2.0 MHz
>
>
>
> At 08:37 PM 12/1/1999 -0700, George K. Watson wrote:
> >
> >Any experiences with this type of noise? Your thoughts,
> ideas, etc. please.
> >
>
> Suggest you or he contact Ed Hare (W1RFI@ARRL.ORG) and look at the
> information on FCC Part 15 Rules to be found on the ARRL's
> Web site in the
> TIS section. Ed may already be working on this problem with the
> manufacturers, and in any case can give you good advice.
>
> 73, Pete N4ZR
> Sometimes a tower is just a tower
>
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>
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