Motorola Cp185 Basic 68007024004 Manual

VHF Specifications1-5
1.5 VHF Specifications
General
Self-Quieter FrequenciesTransmitter
Receiver
All specifications are subject to change without notice.
VHF
Frequency:136 – 174 MHz
Channel Capacity: 16 Channels
Power Supply:7.5 Volts ±20%
Dimensions:
(H x W x D)
with
High Capacity Li-Ion 
NiMH Std
Li-Ion Std
Batteries:120 mm x 55 mm x 40.7 mm 
120 mm x 55 mm x 36.5 mm 
120 mm x 55 mm x 35.5 mm
Weight: 
model with Battery:
High Capacity Li-Ion
NiMH Std
Li-Ion Std
342.0g
394.5g 
335.0g
Average Battery...

1-6Model Charts and Test Specifications: VHF Specifications
Notes 

Chapter 2 Theory Of Operation
2.1 Introduction
This chapter provides a basic theory of operation for the radio components.
2.2 Major Assemblies
• Main PCB – contains the RF circuits which comprises receiver, transmitter, phase-locked loop 
(PLL) frequency synthesizer, micro controller, power supply, audio and digital circuits
• Display and Keypad PCB (Limited and Full Keypad models only) – 8 characters (14 segments 
star burst) and 10 icons with backlighting, liquid-crystal display (LCD)
• Volume Knob...

2-2Theory Of Operation: Major Assemblies
2.2.1.1  RX Front End
UHF2 : Receiver Front-end consists of a low pass filter, a pre-selector filter, a low noise RF Amplifier 
and a Post-selector filter. Incoming RF signal from the antenna is applied through the Harmonics 
Low Pass Filter (L409 – L411, C426 – C429, C445 – C446) and passes through the transmit/receive 
switch (CR301) and a varactor-tuned 2-pole pre-selector filter (L320, L324, C351, C361, CR314 and 
CR307) before routed to an RF amplifier...

Theory Of Operation: Major Assemblies2-3
2.2.1.3  RX Squelch
The mute (squelch) circuitry switches off the audio amplifier when no audio is detected from the 
recovered audio. The squelch circuit main components are U202 & U201. 
U202 will adjust the squelch circuit sensitivity depending on Noise level from recovered audio. Noise 
level is amplified by internal amplifier of U201 to help U202 decide the squelch circuit sensitivity. If 
the noise level is over the set threshold, the microprocessor mutes...

2-4Theory Of Operation: Major Assemblies
The APC (Auto Power Control) keeps the current supplied to Final PA (Q403) constant. Resistor, 
R417 is used for current sensing. The voltage difference ratio of R423 to R417 is amplified through 
U401 and passed to Q404 and Q405 to produce constant power output to the antenna. Do not 
exceed the maximum allowed bias voltage of the device.
2.2.3 Phase Lock Loop Synthesizer
The Phase Lock Loop (PLL) synthesizer subsystem consists of the reference oscillator...

Theory Of Operation: Major Assemblies2-5
2.2.4 RX Audio Circuit
The RX audio circuit consists of Audio Processor IC, Audio amp, speakers & Sub-tone system.
The RX Audio from U201 is channeled to Audio processor IC. VR3 controls the received 
demodulated signal level from -4.0 dB to +3.5 dB in 0.5 dB steps. RX LPF eliminates high-frequency 
audio components > 3 kHz. TX/RX HPF eliminates low-frequency audio components lower < 250Hz. 
Descrambler (if ON) inverts the spectrum distribution of audio signals...

2-6Theory Of Operation: Major Assemblies
2.2.5 TX Audio Circuit
The TX audio circuit is comprised of microphones, LPF, Audio Processor IC, and TX Sub-tone 
system.
The TX audio enters the radio via the internal MIC or external MIC. This TX Audio is filtered through 
a 4th order 4 kHz Low-pass filter (U501-C & D) which prevents aliasing noise from ASIC. TX Audio 
enters the Audio Processor IC which is then directed to an internal Amplifier (TX A1) for gain 
adjustment of audio signal. A HPF (VR1) controls...

Theory Of Operation: Major Assemblies2-7
The output audio signal of Audio Processor IC is directed to volume control switch (SW/VOL1) 
controlled by user and is finally amplified by U601BTL Audio Amplifier to a sufficient level to drive 
either the external or internal speaker.
2.2.6 Microcontroller
The microprocessor or CPU includes Microprocessor (U101), EEPROM and support components. 
Radio operation is controlled by software in internal Flash ROM memory.
Radio parameters and customer specific...

2-8Theory Of Operation: Major Assemblies
Notes