[RFI] Low voltage lighting solid state "transformers"

Tom Rauch w8ji at contesting.com
Sun Dec 17 17:52:15 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.

Technically any spurious emission that causes harmful 
interference to a licensed service is illegal regardless of 
absolute level.
The ARRL also would have had to test the device in the 
actual working situation to be sure it fully complied.

>The FCC radiation limits are not sufficient to prevent
> interference even when the device is within limits.

That's true for certain tests. That's why there is a blanket 
clause that says the licensed service can't suffer harmful 
interference. Of course we all know they won't generally 
enforce that type of rule, but I have seen them enforce it. 
I've seen them enforce it with broadcast stations that had 
harmonics that met spec but caused problems, and alarm 
systems that were incidental radiators.

It is accurate to say the rules prohibit harmful 
interference, but the FCC is no longer run by people who 
understand communications systems. They are all political 
appointees based on who's buddy or son it is---and we keep 
re-electing the same crooked crew.

73 Tom 

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