Section IV
Paragraphs 4-1 to 4-5
SECTION IV
THEORY OF OPERATION
COMPONENTS.
chassis, a univerter chassis, and an audio chassis
which includes the power supply. Figure 4-1 is a
simplified block diagram of the signal generator.
a. The r-f chassis supplies the r-f carrier by mix-
ing the outputs of two crystal-controlled oscillators
supplies the r-f carrier during NAV operation. The
and multiplying the sum frequency to the desired out-
output frequency of 108.0 to 135.9 mc is developed by
put frequency of 108.0 to 135.9 mc for testing navi-
first mixing the output of crystal-controlled fine fre-
gation and localizer receivers (NAV operation).
quency oscillator V1501 (4.875 to 5.100 mc) with the
output of crystal-controlled coarse frequency oscilla-
b. When testing glide slope receivers a frequency
tor V1502 (22. 125 to 28.875 me). Oscillator V1502
range of 329.3 to 335.0 mc is required. For glide
uses the third harmonic of the selected crystal. The
slope operation the output of the r-f chassis is de-
output of V1501 and V1502 is fed to r-f mixer V1503
livered to the univerter chassis where it is mixed
where the sum frequency (27 .000 to 33.9'75 mc) is se-
lected and all other frequencies are rejected. This
w i t h a 200-mc oscillator. The sum frequency of
329.3 to 335.0 mc is then delivered to the GS OUT-
frequency is amplified by r-f amplifier V1504 and fed
PUT jack.
to r-f quadrupler V1505. The fourth harmonic (108.0
to 135.9 mc) is taken from V1505 and delivered to r-f
c. The audio chassis generates the various audio
amplifier V1506. R-f Amplifier V1506 also receives
s i g n a l s required for modulating the r-f carrier.
the selected audio signal from the audio chassis. It is
Stable RC oscillators produce audio frequencies of 30
amplified by a-f amplifier V1507 and fed to V1506
cps, 9960 cps and 1000 cps. By distorting the 30-cps
through modulator V1508. The r-f carrier is modu-
signal and selecting the third and fifth harmonics, 90
lated by the selected audio signal and fed to r-f atten-
cps and 150 cps are also produced. The audio signal
uator Z1502 where the desired amount of attenuation
is delivered to the r-f chassis where it modulates the
occurs depending on the setting of the MICROVOLTS
r-f carrier.
control. The attenuated and modulated carrier fre-
quency is fed through coaxial relay K1401 to NAV
d. The power supply is mounted on the audio chassis
OUTPUT jack during NAV operation and to the uni-
and is a 21-volt dynamotor which furnishes unregu-
verter chassis for GS operation. A portion of the
lated 230 volts and regulated 150 volts for use by all
modulated carrier is fed to demodulator V1509, whose
the signal generator circuits.
d-c output is proportional to the r-f signal amplitude,
Signal Generator SG-13/ARN, Simplified Block Diagram
