Motorola Portable Radio Ep450 Detailled Hkln4216c Manual

Chapter 7 VHF Schematic Diagrams, Overlays, and 
Parts Lists
7.1 Introduction
This section provides schematic diagrams, overlays, and parts lists for the radio circuit boards and 
interface connections.
7.1.1 Notes For All Schematics and Circuit Boards
* Component is frequency sensitive. Refer to the Electrical Parts List for value and usage.
1. Unless otherwise stated, resistance values are in ohms (K = 1000), capacitance values are in 
picofarads (pF) or microfarads (µF), and inductance values are in...

June, 2005HKLN4216C
7-2VHF Schematic Diagrams, Overlays, and Parts Lists: Introduction
7. Circuit Block Interconnection Legend:
301-400 DC Regulation
401-450Microprocessor
451-550 Audio
Name Description
USWB+Unswitched Battery Voltage (always on)
5V 5 volts (regulated)
5R5 volts in RX mode only
5T 5 volts in TX mode only
RESETLow-line reset signal from U320 to uP
D3_3V Digital 3.3 volts (regulated)
3VAnalog 3 volts (regulated)
TX_ENA Transmit enable signal from uP to transmitter
PWR_SETDC voltage from...

HKLN4216CJune, 2005
VHF Schematic Diagrams, Overlays, and Parts Lists: Speaker and Microphone Schematic 7-3
7.1.2 Six Layer Circuit Board
Figure 7-1.  Six-Layer Circuit Board: Copper Steps in Layer Sequence 
7.2 Speaker and Microphone Schematic
Figure 7-2.  Speaker and Microphone Schematic
7.2.1 Speaker and Microphone Parts List
Reference
DesignatorMotorola Part 
No.Description
MK15085880L01Microphone, electret
SP1 5085738Z08
 Speaker assembly with 
connector
LAYER 1 (L1)
LAYER 2 (L2)
LAYER 3 (L3)
LAYER...

June, 2005HKLN4216C
Notes:
7-4VHF Schematic Diagrams, Overlays, and Parts Lists: Speaker and Microphone Schematic 

Chapter 8 403-440 MHz UHF Theory Of Operation
8.1 Introduction
This chapter provides a detailed theory of operation for the radio components. Schematic diagrams 
for the circuits described in the following paragraphs are located in Chapter 13 of this manual.
8.2 UHF Receiver
The UHF receiver covers the range of 403-440 MHz and provides switchable IF bandwidth for use 
with 20/25/30 kHz or 12.5 kHz channel spacing systems. The receiver is divided into two major 
blocks, as shown in Figure 8-1.
• Front End...

June, 2005HKLN4216C
8-2403-440 MHz UHF Theory Of Operation: UHF Receiver
The output of the RF amplifier is applied to the interstage filter, a fixed-tuned 4-pole Butterworth 
shunt-coupled resonator design having a 3 dB bandwidth of 68 MHz centered at 462 MHz, and 
insertion loss of 3.5 dB. This filter yields an image rejection of 58 dB at 350 MHz, assisted by a 
transmission-zero at 300 MHz implemented by C524 for the reasons mentioned above.
The output of the interstage filter is connected to the...

HKLN4216CJune, 2005
403-440 MHz UHF Theory Of Operation: UHF Transmitter 8-3
8.3 UHF Transmitter
The UHF transmitter covers the range of 403-440 MHz. Depending on model, the output power of the 
transmitter is either switchable on a per-channel basis between high power (4 watts) and low power 
(1 watt), or is factory preset to 2 watts. The transmitter is divided into four major blocks as shown in 
Figure 8-2.
• Power Amplifier
• Harmonic Filter 
• Antenna Matching Network
• Power Control.
Figure 8-2....

June, 2005HKLN4216C
8-4403-440 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry
8.3.4 Antenna Matching Network
The harmonic filter presents a 50Ω impedance to antenna jack J140. A matching network, made up of 
C140-C141 and L140, is used to match the antenna impedance to the harmonic filter. This optimizes 
the performance of the transmitter and receiver into the impedance presented by the antenna, 
significantly improving the antennas efficiency.
8.3.5 Power Control
The power control...

HKLN4216CJune, 2005
403-440 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry 8-5
SPI_CLK, and SYNTH_CS (chip select) lines (U409 pins 100, 1 and 47 respectively). A logic high (3 
V) from U201 pin 4 indicates to the microprocessor that the synthesizer is locked.
Figure 8-3.  UHF Frequency Generation Unit Block Diagram
Transmit modulation from the ASFICcmp (U451 pin 40) is applied to U201 pin 10 (MOD_IN). An 
electronic attenuator in the ASFICcmp adjusts overall transmitter deviation by...

June, 2005HKLN4216C
8-6403-440 MHz UHF Theory Of Operation: UHF Frequency Generation Circuitry
One of the auxiliary outputs of the synthesizer IC (AUX3, U201 pin 2) provides the TRB signal which 
determines the operating mode of the VCO, either receive or transmit.
Figure 8-4.  UHF Synthesizer Block Diagram
8.4.2 Voltage Controlled Oscillator (VCO)
The VCOBIC (U251), shown in Figure 8-5, in conjunction with the Fractional-N synthesizer (U201) 
generates RF in both the receive and the transmit modes of...