Motorola Gtx2000 Lcs2000 68p02945c70 O Manual

7-16 Theory of Operationrouted to two attenuators, which are tuned in the factory or the Þeld to set the
proper amount of FM deviation. The TX audio emerges from the ASFIC at
U0201-H8 MOD IN, and is routed to the RF section.
Transmit Signalling
CircuitsSee Figure 7-4 for reference for the following sections. From a hardware point of
view, there are three types of signalling:
¥Sub-audible data (PL / DPL / Connect Tone) that gets summed with transmit
voice or signalling,
¥DTMF data for telephone...

Theory of Operation 7-17 This drives a tone generator inside U0201 which generates a staircase
approximation to a PL sine wave or DPL data pattern. This internal waveform is
then low-pass Þltered and summed with voice or data. The resulting summed
waveform then appears on U0201-H8 (MOD IN), where it is sent to the RF board
as previously described for transmit audio. A trunking connect tone would be
generated in the same manner as a PL tone.
High Speed DataHigh speed data refers to the 3600 baud data...

7-18 Theory of Operation
Receive Audio CircuitsRefer to the following sections.
Figure 7-5 Receive Audio Paths
Squelch DetectThe radioÕs RF circuits are constantly producing an output at the discriminator
(U5201-28). This signal (DET AUDIO) is routed to the ASFICÕs squelch detect
circuitry input SQ IN (U0201-H7). All of the squelch detect circuitry is contained
within the ASFIC. Therefore from a userÕs point of view, DET AUDIO enters the
ASFIC, and the ASFIC produces two CMOS logic outputs based on the...

Theory of Operation 7-19 ACT. The state of CH ACT and SQ DET is high (logic 1) when carrier is detected,
otherwise low (logic 0).
CH ACT is routed to themP pin 25 while SQ DET adds up with LOCK DET,
weighted by resistors R0113, R0114, and is routed to one of themP«s ADC input
U0101-43. From the voltage weighted by the resistors themP determines whether
SQ DET, LOCK DET or both are active.
SQ DET is used to determine all audio mute / unmute decisions except for
Conventional Scan. In this case CH ACT is a...

7-20 Theory of OperationThe outputs of the Audio PA (EXT-SPKR+, INT/EXT SPKR-) are routed to the
external speaker through the accessory connector. The INT/EXT SPKR- is
directly connected to the INT-SPKR(-).
The EXT-SPKR+ can be connected to the internal speaker(+) in two ways: 1)
internal connection via R456 (0 Ohm); 2) Externally, via a jumper between pin 16
and pin 13 of the accessory connector.
The audio power ampliÞer has one inverted and one non-inverted output that
produces the differential audio...

Theory of Operation 7-21
Receive Signalling CircuitsRefer to the following sections.
Figure 7-6 Receive Signalling Path.
Sub-audible Data (PL/DPL)
and High Speed Data DecoderThe ASFIC (U0201) is used to Þlter and limit all received data. The data enters
the ASFIC at U0201-J7. Inside U0201 the data is Þltered according to data type
(HS or LS), then it is limited to a 0-5V digital level. The MDC and trunking high
speed data appear at U0201-G4, where it connects to themP U0101-11.
The low speed limited data...

7-22 Theory of OperationThe allowable internal alert tones are 304, 608, 911, and 1823Hz. In this case a
code contained within the SPI BUS load to the ASFIC sets up the path and
determines the tone frequency, and at what volume level to generate the tone. (It
does not have to be related to the voice volume setting).
For external alert tones, themP can generate any tone within the 100-3000Hz
audio band. This is accomplished by themP generating a square wave which enters
the ASFIC at U0201-C3.
Inside the...

 
Troubleshooting 8-1 
8
 
Troubleshooting
 
Overview
 
This section contains three troubleshooting tables for the following GTX/
LCS 2000 components:  
•  
Receiver  
•  
Synthesizer  
•  
Power Amplifier  
•  
Controller  
•  
Control Head 
Troubleshooting Charts
 
Refer to following pages. 

 
8-2 Troubleshooting
Start
Is K9.1 at  Is AUDIO_DET
Check
Check RX_INJ -50dBmCheck
Check
Check
Check LO_INJ0dBmCheck
Check IF-35dBm
Is 

 
Troubleshooting 8-3
Troubleshooting Flow Chart
for Receiver (cont.)
Check  RF level
Check RF &>-18DBM >-18DBMStart
Check DC at
9.3VCheck DC 
Check ADAPTCheck Check DC at
5VCheck
>1V