Figure 9. Connections for final testing.
cf. Set the audio oscillator frequency to
a. Adjust the AMPLITUDE control on
20,000 cps and repeat the above procedure
the audio oscillator to obtain a reading of
f o r distortion measurement at this fre-
.1 volt on the spectrum analyzer voltmeter.
quency. Distortion should measure below
b. Set the spectrum analyzer function
1 percent. If distortion is below 1 per-
s w i t c h to SET LEVEL and the meter
c e n t within the frequency range of the
range switch to 100% (10 volts). Adjust
spectrum analyzer (20 cps -20 kc), pre-
the spectrum analyzer signal INPUT con-
sume that is is low at higher frequencies.
trol to obtain a full-scale reading on the
e. Disconnect the audio oscillator from
0-1 scale of the spectrum analyzer volt-
t h e rf amplifier INPUT terminals, and
meter.
s h o r t the INPUT terminals on the rf
c. Set the spectrum analyzer function
a m p l i f i e r together with a wire jumper.
switch to DISTORTION and tune the FRE-
f. Set the spectrum analyzer function
QUENCY dial for a dip on the voltmeter.
switch to SET LEVEL and set the signal
R e d u c e the setting of the meter range
I N P U T control to MAX; set the meter
switch as necessary and tune the spec-
range switch to the .03 R.M.S. VOLTS
t r u m analyzer FREQUENCY and BAL-
range. The actual voltage input is now only
A N C E controls for a minimum meter
0.1 (one-tenth) of that indicated on the
reading. The distortion indicated by the
meter. The measured noise voltage should
meter must be less than 1 percent. If it
not exceed 3 millivolts.
is higher, measure the distortion in the
g. Set the amplifier GAIN switch to 20 db.
audio oscillator output alone which should
The spectrum analyzer meter should indi-
be less than 0.5 percent.
cate less than 2.5 millivolts.
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