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Motorola GM950E User Manual

Motorola GM950E
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Transmit Audio Circuits
6.3-8 Theory of Operation
The FLAT TX AUDIO signal from accessory connector U0400-5 is buffered by Op-amp U0106-1 and
fed to the AFIC U0103-13 through gate U0107-1. Gate U0107-1 is controlled by the µP port PC7
(U0101-42) and selects between FLAT TX AUDIO or signalling signal created by the µP.
Figure 6.3-1 Transmit Audio Paths
4.2 External Mic Path
The external microphone signal enters the radio on accessory connector J0400 pin 2 and connects
to the standard microphone input through R0421.
4.3 PTT Sensing and TX Audio Processing
Mic PTT is sensed by the µP U0101 pin 22. An external PTT can be generated by grounding pin 3
on the accessory connector if this input is programmed for PTT.
The MIC signal is routed to the AFIC (U0103) through R0146 and R0145 (GM950E radio) or through
Op-amp buffer U0106-2 and option board connector J0103-3,1 (GM950i radio). R0145, C0145, the
amplifier inside the AFIC (pins 9,10) and gain setting resistor R0147 pre-emphasise the MIC audio
signal. After further limiting and filtering the modulation signal emerges from the AFIC at U0103-19/
20. Both signals are weighted by resistors R0181, R0182 and add up to signal MOD IN.
TO
RF
SECTION
(SYNTHESIZER)
J0103-1
J0400
ACCESSORY
CONNECTOR
J0101
CONTROL HEAD
CONNECTOR
MIC
EXT MIC
FLAT TX
AUDIO
J0103-3
5
16
GEPD 5427-1
2
13
10
19
20
21
14
15
MOD IN
IN
OUT
OPTION
BOARD
FILTERS AND
PREEMPHASIS
LIMITER
ASFIC
U0201
TX OUT
AUX
TX IN
SPLATTER
FILTER
4-BIT
DEVIATION
ATTENUATOR
5-BIT
DEVIATION
ATTENUATOR
TX IN
http://www.myradio168.net

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Motorola GM950E Specifications

General IconGeneral
BrandMotorola
ModelGM950E
CategoryRadio
LanguageEnglish

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