Ericsson KRD 103 117/1, Maintenance Manual, Page: 3 / 54

GENERAL
The NPC-200 VHF Portable Radio Unit operates in the
148-174 MHz frequency band with a power output of 5 or 1
watt (selectable). It has programmable features that permit a di-
verse range of features for the user.
The NPC-200 UHF Portable Radio Unit operates in the
438-470 MHz frequency band with a power output of 4 or 1
watt (selectable). It has programmable features that permit a di-
verse range of features for the user.
General operating procedures are contained in the applica-
ble Operator’s Manual.
CIRCUIT DESCRIPTION
The NPC-200 Portable Radio Unit Block Diagram is
shown in Figure 1. The radio consists of the following boards.
•
Main
The receiver and transmitter sections, logic section and
regulators.
•
Sub
The microphone amplifier, pre-emphasis and limiter,
microphone mute circuit, low pass filter, 2-tone decoder
and CTCSS bandpass filter.
•
RF
The first RF amplifier and first mixer sections of the
receiver.
•
VCO
Two voltage controlled oscillators for the receiver and
transmitter.
•
PLL
The phase locked loop with a prescaler, reference crystal
oscillator and charge pump circuit.
•
Switch
The transmit harmonic filter and antenna switch.
SYNTHESIZER
The synthesizer produces a stable RF frequency that is the
transmit frequency in the transmit mode and the receive first
local frequency in the receive mode.
The synthesizer consists of a phase locked loop (PLL) with
a prescaler, a reference crystal oscillator, a voltage controlled
oscillator (VCO), a transmit local oscillator and a charge pump
circuit.
When the operating channel of the radio is changed, the
microprocessor IC601 provides PLL IC301 with channel fre-
quency information. IC301 has three counters, a fully program-
mable reference counter, "N" and "A" counters. IC601-13 sup-
plies serially 16-bit and 19-bit of data to IC301-10. IC601-14
supplies clock pulses to IC301-9. IC601-49 supplies latch en-
able pulse to IC301-11. The appropriate counter latch receives
this data according to the last data bit (control bit) of each data
string entered.
The 12.8 MHz reference oscillator frequency (X301) is di-
vided by the reference counter. The dividing ratio is 1/2560 &
1/2048 for 5 kHz or 6.25 kHz channel step (VHF) or 1/1024
for 12.5 kHz channel step (UHF). The internal prescaler di-
vides the VCO frequency supplied to the PLL into a kHz-order
frequency. The resulting frequency is then divided by the "N"
and "A" counters. The internal phase detector circuit compares
the output of the reference counter to the output of the "N" and
"A" counters and issues error signals at pins 15 and 16. These
error signals pass through the charge pump circuitry (Q301)
and force the VCO frequency higher or lower until a LOCK
condition occurs.
The VCO circuit consists of Q201 for the receiver, Q204
for the transmitter and Q202 for the buffer-amplifier. Q203 en-
ables the receive VCO in the receive mode while Q205 enables
the transmit VCO in the transmit mode.
The VCO output signal enters the phase detector (pin 8 of
IC301) through a buffer-amplifier Q302 and keeps it phase so
no frequency changes are detected. The internal phase detector
of the PLL IC senses a phase difference between the divided
VCO frequency and the reference oscillator frequency. A logi-
cal low level is set at pin 7 of IC301 to indicate an out-of-lock
condition of the PLL. This signal is sent to the transmit inhibit
circuit through inverters Q303 and Q504. When the PLL is in
the locked condition, pin 7 of IC301 is set to a logical high.
The synthesizer frequency stability over temperature is
maintained within
±
5.0 PPM between -30°C and +60°C.
The transmit audio signal and the transmit sub-audible sig-
nal are applied to the variable capacitor diodes (D202 through
RT202 and RT201 in the VCO section and D302 in the PLL
section). RT202 adjusts the maximum deviation and RT201 ad-
just a balance of modulation between the VCO and the refer-
ence oscillataor. CT301 in the PLL section adjusts the
oscillation frequency of X301.
In the receive mode the VCO oscillates 59.85 MHz below
the receive frequency. The receive mixer circuitry produces the
first IF frequency (59.85 MHz) from the received signal and
the receive local frequency (VCO output).
SPECIFICATIONS*
VHF GENERAL
Regulatory Approval
FCC AMWUL087
DOC 287 195 103
Channels 16
Frequency Range 146-174 MHz
Channel Spacing 30 kHz (5 kHz/6.25 kHz step programmable)
Size 144 mm (H) x 60 mm (W) x 45 mm (D)
Weight 460 grams
Operating Temperature -30°C to +60°C
VHF TRANSMITTER
Output Power 5.0 or 1.0 Watt (selectable)
Frequency Stability
±
3 PPM
Spurious Emission -65 dBc
Hum and Noise 40 dB
Maximum Deviation
±
4.5 kHz (@100 mV input with CTCSS tone)
VHF RECEIVER
Sensitivity (12 dB SINAD) 0.25
µ
V
Squelch Sensitivity 0.15
µ
V
Intermodulation Rejection 70 dB
Spurious Response 80 dB
Adjacent Channel Selectivity 73 dB
Hum and Noise 42 dB
Audio Frequency Response +6 dB at 500 Hz, -6 dB at 2000 Hz @ 1 kHz reference
UHF GENERAL
Regulatory Approval
FCC AMWUL086
DOC 287 195 102
Channels 16
Frequency Range 438-470 MHz
Channel Spacing 25 kHz (12.5 kHz step programmable)
Size 141 mm (H) x 60 mm (W) x 45 mm (D)
Weight 460 grams
Operating Temperature -30°C to +60°C
UHF TRANSMITTER
Output Power 4.0 or 1.0 Watt (selectable)
Frequency Stability
±
3 PPM
Spurious Emission -65 dBc
Hum and Noise 40 dB
Maximum Deviation
±
4.5 kHz (@100 mV input with CTCSS tone)
UHF RECEIVER
Sensitivity (12 dB SINAD) 0.25
µ
V
Squelch Sensitivity 0.15
µ
V
Intermodulation Rejection 70 dB
Spurious Response 80 dB
Adjacent Channel Selectivity 70 dB
Hum and Noise 42 dB
Audio Frequency Response +6 dB at 500 Hz, -6 dB at 2000 Hz @ 1 kHz reference
* These specifications are intended primarily for use of the service technician. Refer to the appropriate Specifications
Sheet for the complete specifications.
AE/LZB 119 1658 R1A
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