Broadcast Electronics Marti Electronics ME-40, Руководство пользователя

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40
©2011 Broadcast Electronics
A sample of the modulated oscillator output frequency is compared to a precision reference
frequency in a comparator circuit which generates a correction voltage. This correction voltage is
applied to the modulated oscillator to maintain the stability of the carrier frequency. If the carrier
is off frequency (as when power is applied), the AFC/PLL circuitry will mute the RF output until the
carrier is locked in-phase with the reference frequency. A dual speed PLL filter ensures rapid
stabilization of the carrier frequency.
In addition, the AFC/PLL circuit board accepts, sums, and pre-corrects audio input signals to
provide a linear response when applied to the modulated oscillator.
Refer to the table for electrical characteristics relative to the AFC/PLL circuit board.
TABLE 5-5. ELECTRICAL CHARACTERISTICS – AFC/PLL Circuit Board
PARAMETER SPECIFICATIONS
INPUTS:
RF SAMPLE
BALANCED AUDIO
COMPOSITE
AUDIO
SCA
AUDIO
OUTPUTS:
MODULATION
AFC
AFC (Metering)
AFC INTERLOCK
EXTERNAL
LOCK INDICATOR
COMPOSITE AUDIO (Metering)
COMPOSITE
TEST
1 mW at 50 Ohms
+10 dBm at 600 Ohm for 100% Modulation
3.5V p-p (1.24V RMS) for 100% Modulation
3.5V p-p (1.24V RMS) for 10% Injection
3.5V p-p, Nominal for +/- 75 kHz Deviation
+2.0V DC to +9.0V DC, Dependent upon RF
Center Frequency
+2.0V DC to +9.0V DC, Dependent upon RF
Center Frequency
Open Collector Output
Open Collector Output
6.0V p-p at 1 k Ohm
6.0V p-p at 1 k Ohm
5.11.1
REMOVAL AND INSTALLATION
REQUIRED EQUIPMENT. A #2 Phillips screwdriver with a 4 inch (10.16 cm) blade is required to
remove the AFC/PLL circuit board assembly from the exciter chassis.