postmaster@CUVMB.CC.COLUMBIA.EDU (01/11/90)
SB ALL@ALLBBS $923_WA2ISE
Florescent RFI reduction
Here is something to try when confronted with RFI from a florescent
light. I found that connecting a 0.01 to 0.1 uF @ 1.4kV capacitor will help
reduce the RFI in most cases. Connect it like this:
__________
------ballast----I lamp I------
120V ---I__________I-- /
\ / /
\---starter---/ /
\ / /
--capacitor /
return /
____________________________/
The 2 pins on one end of the bulb are connected to a heater filament,
and likewise on the other end. You should connect the cap so that it
has to go thru one or both filaments before it reaches the ballast
and/or the return side of the power line. This will make the filaments
act like a fuse if the cap shorts out. Be sure to use a capacitor
rated at least 1.4KV. The starter makes a large inductive spike when
it starts the bulb. It's also a good idea to use high rated parts if
you install this cap in a fixture attached to the house, for safety
reasons. And be sure to make sure that, when installed, the leads of
the cap are well insulated and can't short to anything. For florescent
lights that don't have starters, you could try putting the cap across
the bulb like above. In this case, You'll have to depend on the
ballast itself to limit current if the cap shorts. Use a higher
voltage cap like 5KV in 2X40W fixtures. Just be sure that you don't
create a safety hazard when you do this! So, proceed with caution, at
your own risk. Near as I can tell, this has no effect on bulb life.
73 de WA2ISE