Pulsar TCF-10B, System Manual, Page: 119 / 249

R29 Sets the offset in output amplifier, so
that when 0 dBm is generated, R29 is
adjusted to minimize the 2nd harmonic
distortion
Capacitor
C19 Adjustment for 3.27680 MHz clock
oscillator
Switch
S5 Frequency-shift select
Test Point
TP1 Clock Oscillator Output
11.2 TRANSMITTER CIRCUIT
DESCRIPTION
The function of the Transmitter Module (see
Figure 11-2, Schematic 1355D71) is to provide
the RF signal (0 dBm/.001W, 50 ohm balanced),
which drives the 10W
PA Module. The
Transmitters frequency range is from 30 kHz to
535 kHz, programmable in 0.1 kHz (100 Hz) steps
by four rotary switches on the Transmitter. The
Transmitter Module operates from keyed inputs
(set by jumpers at the Keying Module):
• High-Level (10W) Key (pins C/A-8)
• Any Transmitter Key (pin A-10)
• Voice Key (pins C/A-6)
• Shift High (pin C-10) (TCF–10B Only)
• Shift Low (pins A/C 24) (TCF–10B Only)
The Transmitter Module also operates from an
audio signal from the Optional Voice Adapter
Module: AM Voice (pins C/A-26). Refer to Figure
11-3, Transmitter Block Diagram.
Frequencies are selected using the four BCD
(Binary Coded Decimal) switches (SW1 thru
SW4); the range is from 30.0 to 535.0 kHz, in
0.1 kHz (100 Hz) steps. The 15-bit output of the
BCD switches is converted to a 13-bit binary
number by the BCD-to-Binary converter (ROMs
I1 and I2).
The 13-bit output of ROMs I1 and I2 provides an
input to the Shift and Control Logic (I3), which
consists of three parts:
1. A full adder/subtracter which functions under
control of:
• Shift High (Add)
• Shift Low (Subtract)
2. A frequency-shift, in 50 Hz increments from 0
to 750 Hz, selected by the 4-position DIP
switch (S5).
3. A sequencer and multiplexer (MUX) which
provides the following outputs to the
Numerical Controlled Oscillator (NCO I4):
• Address select (ADDR)
• Write (WRN)
• Load (LDSTB)
• 2 (8-bit sequential) data bytes
The NCO (I4) generates digital sine functions of
very precise frequency, to be used in conjunction
with a D/A converter (I5) in analog frequency
generation applications. The NCO is designed to
interface with and be controlled from an 8-bit bus.
The NCO maintains a record of phase which is
accurate to 16 bits. At each clock cycle, the
number stored in the 16-bit phase register is added
to the previous value of the phase accumulator.
The number in the phase accumulator represents
the current phase of the synthesized sine function.
The number in the
D
-phase register represents the
change of phase for each cycle of the clock. This
number is directly related to the output frequency
by the following:
f
C
x
D
- phase
f
0
= —————
2
16
where: f
0
is the frequency of the output signal
and: f
C
is the clock frequency (3.27680 MHz)
Page 11–2 April 1997
TCF–10B System Manual
Technologies, Inc.