[RFI] Low voltage lighting solid state "transformers"
n6kj.kelly at gmail.com
Sun Dec 17 17:17:16 EST 2006
It may not violate FCC regulations. I bought some LV landscape lights
about 3 or 4 years ago along with a cheap power supply made by
"Hampton Bay" for Home Depot. This thing generated about S7 or S8
noise on 20 meters from 100 feet away and wiped out the AM BC radio in
my care from about 50 feet away or so. It was hideous. I replaced it
with a Malibu transformer and all was well. I sent the power supply
to ARRL headquarters and they tested it. The emissions were not
strong enough to violate FCC regulations yet the noise was very
strong. The FCC radiation limits are not sufficient to prevent
interference even when the device is within limits.
On 12/17/06, Jim Brown <jim at audiosystemsgroup.com> wrote:
> On Sun, 17 Dec 2006 11:07:56 -0700, Steven Farmer wrote:
> >Since my rfi seems to be mostly a common mode problem, some
> >sort of emi filtering at their breaker panel might also work.
> I doubt it. The AC wiring between the noise source and the filter will
> act as an antenna, and in a typical building, is likely to be long
> enough to be a pretty effective radiator on the HF bands. Now, IF the
> AC wiring happens to be in grounded metallic conduit that is properly
> bonded at both ends (or at least bonded to the noise source), you are
> in FAR better shape. That's more likely to be the case in an industrial
> building, less likely in residential. And even in industrial buildings,
> I'm seeing a lot more PVC pipe rather than EMT, because it's a lot
> cheaper to install. That, of course, provides no shielding at all.
> The depressing thing about all of this is that everyone involved is
> playing cheap, and we pay the price. Cheap power supplies, cheap
> electrical, no filters, cheap Congress (no funding for FCC to enforce
> its rules), and in the case of these devices, rules (Part 18) that seem
> to allow this garbage equipment to be sold.
> Perhaps someone working in the EMC world might venture an opinion as to
> whether there might be grounds for approaching FCC on this issue. The
> lighting people will tell you that their stuff is exempt under Part 18.
> Jim K9YC
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