Uhf1 Schematic Diagrams, Overlays, And Parts Lists; Introduction - Motorola EP350 Service Manual

Chapter 13 UHF1 Schematic Diagrams, Overlays, and

13.1 Introduction

This section provides schematic diagrams, overlays, and parts lists for the radio circuit boards and
interface connections.
13.1.1 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
nanofarads (nF), picofarads (pF) or microfarads (µF), and inductance values are in
nanohenries (nH) or microhenries (µH).
2. DC voltages are measured from point indicated to chassis ground using a Motorola DC
multimeter or equivalent. If the board has been removed from the chassis, the transmitter
module mounting screws may be used for ground connection. (Note: The antenna nut
bracket is connected to ground.) Operating mode dependent voltages are followed by (RX)
for receive mode, (TX) for transmit mode, (UNSQ) for unsquelched mode, etc.
3. RF voltages on VHF models are measured with a Fluke model 85 RF probe. The indicated
voltages expressed in mV (RF) are DC level readings which correspond approximately 1:1 to
the RF voltage level in mV rms. RF voltages in the Receiver Front End and Receiver Back
End circuits are measured with an on-channel 1mV (-47dBm) RF signal applied to the
antenna jack ANT1/ANT.
4. RF voltages on UHF models are measured both with a high–impedance RF voltmeter having
a bandwidth in excess of 500 MHz (levels are expressed in dBm) and with a Fluke model 85
RF probe [levels are expressed in mV (RF)]. These indicated voltages are DC level readings
which correspond approximately 1:1 to the RF voltage level in mV rms, and are only
approximate for UHF frequency measurements. RF voltages in the Receiver Front End and
Receiver Back End circuits are measured with an on-channel 1mV (-47dBm) RF signal
applied to the antenna jack ANT1/ANT.
5. Audio voltages are measured with a high-impedance AC rms voltmeter. The indicated
voltages are expressed in mV rms. Receive mode voltages are followed by (RX) and are
measured with an on-channel signal with 1 kHz modulation at 60% deviation (3 kHz for 25
kHz channels, or 1.5 kHz for 12.5 kHz channels). Transmit mode voltages are followed by
(TX) and are measured with a 1 kHz, 10 mV rms signal present at the external microphone
input (accessory connector J601).
Parts Lists