ballast interference

To: aquatic-plants at actwin_com
Subject: ballast interference
From: Frank Ball <frankb at cougar_sr.hp.com>
Date: Sun, 29 Dec 1996 11:21:36 -0800 (PST)


& Subject: Re: ballast interference
 
I don't have experience quieting down noisy ballasts, but I have worked
with a number of other EMI (ElectroMagnetic Interference) problems.

Interference can be caused by conducted or radiated signals, or both.
Conducted signals come out through the power line and get into the TV
through it's power cord.  To fix it put a filter on the power line of
the unit generating the interference, as close to the ballast as
possible to prevent the power cord from radiating interference.  The
clicks and pops when a light turns on are both conducted and radiated,
but my GUESS is that any buzzing when the unit is running is radiated
interference, but the only way to tell for sure is to experiment.  The
electronic ballasts need to switch on and off to work right.  If the
ballast is a poor design that emits a lot of radiated noise on the
outputs then you probably can't fix that easily, but you can reduce the
amount it radiates.  The wires going from the ballast to the bulbs act
as antennas to radiate the interference signals.  Bundle the wires
tightly together, or better yet, twist or braid them together.  Keep the
wires as close as possible to a grounded reflector or metal hood.  Also
if the ballast itself is not sheilded than a grounded metal sheild
around the ballast may quiet things down.


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	Frank Ball           1UR-M      frankb at sr_hp.com
 	Hewlett-Packard 		(707) 794-4168 work
	1212 Valley House Drive    	(707) 794-3038 fax
	Rohnert Park CA 94928-4999	(707) 538-3693 home
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