9
1. Turn trimmer RV1 to its centre position.
2. Connect a power supply :
AC, 9 to 12 V then between points GND and V.
DC, 12 to 15 V (battery or power supply) then
-
to GND and
+
to V.
3. Connect the output (OUT, GND) to the input of a spectrum analyser, using a screened flex (screen to GND).
Now adjust the noise signal using trimmer RV1 so as to obtain as flat a reproduction characteristic as possible. Especially
pay attention to the higher frequencies (adjust spectrum analyser sensitivity if necessary).
Remark:
the nature of the lower frequencies (32 and 64Hz) makes their read-out unstable.
FOR THOSE WHO LIKE TO EXPERIMENT :
By adapting C1 you can also modify the clock frequency (pin 3 of IC2) of the
shift register (e.g. C1=18pF for a clock frequency up to and beyond 500KHz), so as to obtain a "white noise" at 500KHz and
to adapt the filter (C2=100pF, do not fit C4 through C9). Output voltage will drop down to +/- 100mV RMS.
Test & adjustment
H4301IP'1_rev2.pub
page 9
Thursday, July 12, 2012 10:18
