General Description - Boonton 232-A Instruction Manual

BOONTON RADIO CORPORATION
GENERAL DESCRIPTION
SECTION 1
GENERAL DESCRIPTION
FUNCTION
'The Glide Slope Signal Generator Type 232-A is
designed primarily to test and calibrate Glide Slope re-
ceivers that are part of the aircraft Instrument Landing
System commonly known as the "ILS".
The "ILS" consists of three basic elements: marker
beacons, localizer and glide slope path signals. These
elements, functioning independently, enable an incom-
ing aircraft to locate itself at the threshold of the run-
way with the correct heading, altitude and airspeed in
order to execute a safe landing under low ceiling and
visibility conditions. The elements may be briefly
described as follows:
l. The marker beacons are low power transmitters
which radiate vertically in a cone shaped pattern hav-
ing a elliptical cross-section. The markers, operating
at a frequency of 75 mc, are located along the approach
path and serve to indicate the progress of the aircraft
toward the runway.
2. The localizer radiates a narrow bi-directional
field pattern which establishes the correct final ap-
proach and landing course, enabling the landing air-
craft to arrive at the threshold of the runway flying di-
rectly down the center. Operation is in the vhf range
between 108.1 and 111.9 mc.
3. The glide slope path is a narrow sloping pat-
tern which brings the landing aircraft down at the cor-
rect descent angle in order to clear all obstructions and
arrive at the threshold of the runway at the correct
landing altitude. Operation is in the uhf range be-
tween 329.3 and 335 mc.
The localizer and glide slope patterns are similar
in that for each a single carrier is modulated simul-
taneously with both 90 and 150 cycle tones. The an-
tenna system of each is such that a 90 cycle tone is
radiated to one side of a precisely oriented dividing
plane and a 150 cycle tone is radiated to the other side,
while in the plane itself (actually a narrow angular
sector) equal proportions of both signals exist. The
glide slope center plane is 1^ wide and slopes up from
the runway at an angle of approximately 21⁄°. The
localizer is vertical and oriented along the center line
of the runway.
Localizer radiation is in a horizontal plane while
the glide slope signal is normally radiated at an ob-
. lique angle of 212? from the threshold of the runway.
The signal element with which the Glide Slope
Generator is concerned is the glide slope path. The
Generator accomplishes its functions of test and cali-
bration of the Glide Slope receiver by reproducing the
signal that exists along the glide path, thus simulating
operational conditions. Accordingly, the instrument
хро 22.
provides 20 crystal controlled rf frequencies between
329.3 mc and 335 mc in 0.3 mc incremental steps and
an i-f signal generated by a crystal controlled circuit
designed to operate at any desired point between 15
and 30 mc with the appropriate crystal.* Both rf and
i-f signals can be modulated with a dual signal of 90
and 150 cycles. "Above Course", "On Course", and
"Below Course", signals are simulated by varying
the ratio of modulation of these tones to each other
through a differential attentuator (DB Tone Ratio
Control).
DESIGN
The instrument is contained in a single cabinet
and consists of the following electronic units: (See
Figure 10).
Unit Location
RF Generator Front Left
IF Generator Front Left
Modulation Amplifier Rear Center
1000 Cycle Oscillator Front Right
Metering Circuits Front Right
Tone Generator Circuits Rear Center
Power Supply Rear Right
The above units comprise a chassis that is easily re-
movable from its aluminum frame. Rigid handles are
mounted on the front panel for carrying the instru-
ment.
The rf, i-f sub-assembly is completely shielded and
accessible by the removal of the screws holding the top
and bottom covers. The dual alternator can be re-
moved by simply taking out the four mounting bolts
that hold it.
ACCESSORIES SUPPLIED
1. 6 db attenuator adapter — 50 to 50 ohms un-
balanced, BNC to BRC Type 505-B.
2. 6 db attenuator adapter — 50 ohms unbalanced
to 05 ohms balanced. BINC to small twin uhf —
BRC Type 507-B.
3. I-F Output Cable — 50 ohm internal termina-
tions, clip leads — BRC Type 514-B.
í. Patch Cable — BNC to BNC — 6 feet. BRC
Type 506-B.
SPECIFICATIONS
(Unless otherwise noted, specifications apply to
both rf and i-f output).
Frequency Range:
RF — 329.3 to 335 mc in .3 mc increments (20
channels).
*The instrument is furnished with ап i-f frequency crystal ој
20.7 mc.