RE: Noise

["George Andrews" <mauser2@erols.com>]

Tim and Olga:
	First step I would take is to look at the line voltage. See if the "noise"
is found there. If you have a dual trace or two scopes, monitor the location
where you have found the "noise" and the AC line. If on the line voltage,
commercial filters may eliminate the problem. How well the filters work
depends on the amplitude of the "noise".
	If it is not found on the line, as others have indicated, check for
unterminated coax cable connections. It may also be a problem with a bad
coax cable, so check all your cables.
	There may be other electronic equipment in the room utilizing what is
called a "switching" power supply. This is a method of producing DC power
that also produces RF noise. I do not know the frequency noise that might be
produced. The source of the noise could be right in the room!
	Hope this is of some help.

George Andrews
mauser2@erols.com
N1YAE
AAR1CT
> -----Original Message-----
> From: radsafe@romulus.ehs.uiuc.edu
> [mailto:radsafe@romulus.ehs.uiuc.edu]On Behalf Of olga fernandez-flygare
> Sent: Tuesday, September 01, 1998 3:58 PM
> To: Multiple recipients of list
> Subject: Noise
>
>
> Hello Radsafers:
>
> While trying to trace the source of noise in our gamma
> spectroscopy system,
> we observed a transient sinusoidal signal on our oscilloscope. We estimate
> the frequency to be 0.9-1.0 MHz.
> It appears to be a repeatable but not periodic radiofrequency signal.
>
> Have you observed a similar phenomenon? Any ideas on the source of this
> noise (we are in the basement of UCLA medical center)?      Any RF
> shielding solutions?
>
> Any help would be appreciated.
>
> Sincerely,
>
> Tim Paul + Olga Fernandez-Flygare
> UCLA Radiation Safety Division
> (310) 794-7365
> (310) 206-5550
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