[RFI] Need a lightbulb photocell suggestion

[Jim Brown]

On 11/12/2011 1:20 PM, Howard Lester wrote:
> I bought a screw-into-an-outdoor-light-socket photocell in which you then
> screw in a lightbulb. The photocell, of course, would keep the light off
> during the day, on at night (or maybe during a total solar eclipse, too).
> But the one I bought at Lowe's (I didn't note the brand) put out tremendous
> nighttime RFI, at least on AM Broadcast, and that is entirely unacceptable.
> Do any of you know of a good brand of these things?

That's unlikely. :(   You MIGHT be able to kill the RFI with your 
installation by one or both of the following:

1) A suitable capacitor ACROSS the line -- that is, between Line (Hot) 
and Neutral (White). To be safe, this must be a cap rated for the high 
voltage spikes that often occur on the power line (3-6kV). This requires 
a cap with an X2 rating.  I would choose a value on the order of 0.05uF 
(50 nF). The leads should be VERY short. The capacitor should be right 
at the noise source, on the line side.

2) A suitable common mode choke, formed by winding all three of the 
power conductors for at least ten turns through a #31 ferrite toroid, or 
5-7 turns through .one of the "biggest #31 clamp-ons" (1-in i.d., about 
1.5 inches long)  listed in Appendix One of my RFI tutorial.  The choke 
should be very close to the offending fixture.

I would try the capacitor first, both because it's the mostly likely 
fix, and because it's the easiest and lowest cost.

73, Jim Brown K9YC