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BOONTON
RADIO
CORPORATION
THEORY OF OPERATION
If the Carrier frequency is changed, set the Carrier
Monitor meter to the red line, then reset Percent Mod-
ulation meter to the figure noted previously with the
DB Tone Ratio switch on 0 DB position. Alternatively,
the modulation can be reset by checking the 90-150 ~~
modulation at the 4096 level as above.
MODULATION:
1000 —
Select the desired carrier frequency and set Mod
switch to 1000 —— .
Set the Mod Level control at mid-rotation and set
the 1000 cycle control behind the door to 40% mod-
ulation as indicated on the Percent Modulation meter.
Any desired percent modulation can now be selected
by means of the Mod Level control.
EXTERNAL
MODULATION
Select the desired carrier frequency. Set Mod switch
to Ext. Using an external audio source, apply the mod-
ulation signal to the Ext Mod Input jack. The require-
ment for 10096 modulation is approximately one volt.
The percent modulation
can be varied by the Mod
Level control.
SECTION
ПІ
THEORY
OF OPERATION
BLOCK
DIAGRAM
Figure 2 shows the functional block diagram of
the Glide Slope Generator Type 232-A. It consists of
six electronic units plus a power supply in a single
case—
RF Generator
IF Generator
Modulation Amplifier
1000 Cycle Oscillator
Metering Circuits
Tone Generator Circuits
RF, IF Generators
Separate crystal controlled oscillators are used to
generate the rf and i-f signals. Each oscillator is fol-
lowed by the necessary multiplier stage (or stages) to
produce the specified output frequency. Each section
has its own
demodulator,
but a single cathode
fol-
lower is switched to serve as an impedance transformer
for the section in use.
Two
piston type attenuators,
having a common
drive system and dial calibration, but otherwise func-
tioning as independent units, couple the rf and i-f out-
puts to the panel receptacles.
Standardized rf and i-f output is obtained by hold-
ing the output voltage across each of the final tank
circuits at a fixed level. This is monitored by the Car-
rier Monitor
meter, which
reads the rise in demod-
ulator output voltage due to the carrier and which is
always set to read at its red line.
Modulation
Modulation
of the rf carrier is accomplished
by
simultaneously
plate
modulating
both
the
output
doubler and the preceding doubler stages. Both the ac
modulating voltage and the necessary dc plate voltage
for the two stages are obtained from a circuit con-
nected to the plate of the second modulator amplifier.
The
percent
modulation
is held esentially constant
over a wide range of settings of the Carrier Adjust
control, thus reducing the need for resetting the Mod-
Level control
to maintain
the required
modulation
percentage.
Modulation of the i-f carrier is produced by both
screen and plate control of the pentode output stage,
but is otherwise similar to the r-f modulation.
Percent
modulation
is indicated
by an
average
reading type of ac vacuum tube voltmeter which reads
the ac component of the demodulated carrier. This is
calibrated
to
read
directly
in percent
modulation
(when the Carrier Monitor meter has been set to the
red line).
90 and 150 cycle tone modulation is provided by a
system
consisting of a dual alternator
driven
by a
synchronous
motor,
a harmonic
filter with separate
sections for each of the tones, and a precision resistive
mixing network. Switch positions are provided for in-
dependent adjustment of the level of each of the tones,
and accurate ratio steps of 0 db 0.5 db, 2.0 db, and `
3.3 db, with either tone predominant, are provided.
The carriers can also be modulated
by the 1000
cycle tone from the integral RC oscillator or by an
external source.
The modulation amplifier provides sufficient amp-
lification and power output to allow 10096 modulation
of the carrier by the self contained sources or from an
external source of at least 1.5 v.
DETAILED
OPERATION
In the following sections the order of discussion
follows the order of the functions of an elementary
signal generator to which are added the various special
circuit features required for operational simulation of
the Glide Slope signal.
ESO
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