TM 11-6625-1633-45
CHAPTER 2
FUNCTIONING OF EQUIPMENT
ing the amount of deviation from the rf center fre-
2-1. Block Diagram Analysis
quency. The proper meter multiplier is selected by DE-
VIATION METER RANGE selector switch S3. The
output of amplifier A1V3 is applied through deviation
The AN/URM-149 is a signal source capable of pro-
meter adjustment resistor R1 to deviation meter M1.
ducing unmodulated or frequency modulated (fm) sig-
nals in the 600 to 1,850 megahertz (MHz) range. The
d. Klystron Oscillator Circuit. The klystron oscillator
radio-frequency (rf) output can be modulated by an in-
circuit generates rf voltages within the range of 600
ternal or externally generated sine wave to produce fre-
MHz to 1,850 MHz. The rf output is applied to RF
quency modulation of the rf carrier at a controlled de-
OUTPUT jack J5 through contacts of coaxial relay K4.
viation range of 0 to 300 kilohertz (KHz). The rf output
can also be pulse modulated by an externally produced
e. Power Monitor Bridge Circuit. The power monitor
pulse to produce step voltages. A continuous wave (cw)
bridge circuit is essentially used to measure the average
output is produced when no modulation is applied to the
power level of the klystron oscillator rf output. The os-
rf carrier.
cillator output is applied to the circuit through contacts
of probe switching relay K3.
a. Internal Modulator-Oscillator Circuit. The inter-
nal modulator-oscillator circuit is used for internal
f. Power Supplies.
modulation of klystron oscillator A4V1. It is a sine wave
source capable of producing five output frequencies:
(1) Reflector and beam power supply. The reflec-
1,000 hertz (Hz), 1,600 Hz, 20 KHz, 68 KHz, and 108
tor power supply provides regulated -650 volts, direct-
KHz. The circuit consists of five bridge-tee networks,
current (vdc) to the reflector of klystron oscillator A4V1.
oscillator V1, cathode follower V2, and amplifier V3..
The beam power supply provides -325 vdc for the cath-
The sine wave output is applied through MODULA-
ode of klystron oscillator A4V1.
TION selector switch S2 to amplifier A1V1 (b below).
DEVIATION control resistor R35 determines the input
(2) Modulator and bridge power supply. The
level of the signal applied to A1V1.
modulator and bridge power supply consist of two regu-
lated- power supplies operating from separate secondary
b. Modulation Amplifier Circuit. The modulation
windings of the same power transformer. One supply
amplifier circuit, consisting of amplifier A1V1 and
furnishes +250 vdc for the modulator and the other fur-
cathode follower A1V2, receives modulating signals
nishes -108 vdc for the power monitor bridge.
from the internal modulator-oscillator circuit (a above)
or from EXT PULSE or EXT SINE input jacks J1 and
(3) Klystron filament power supply. The klystron
J2, respectively. The amplified signal is applied directly
filament power supply is a transistorized, low ripple,
from cathode follower A1V2 to the modulation tracking
regulated power supply that provides 6.3 vdc for the
system in the klystron oscillator circuit where it is used
klystron filament.
to modulate klystron oscillator A4V1 by varying the
reflector voltage. A portion of the output from cathode
2-2. Analysis of Internal Modulator-
follower A1V2 is also applied through DEVIATION
METER RANGE selector switch S3 to the deviation
Oscillator Circuit
metering circuit (c below).
c. Deviation Metering Circuit. The deviation meter-
a. The frequency of oscillation of the internal modu-
ing circuit amplifies and rectifies a portion of the output
lator-oscillator circuit is controlled by the bridge -tee
of cathode follower A1V2 (b above) for use in calibrat
2-1
