UG-001 Daniels P25 Radio Systems
www.danelec.com
Chapter 4: P25 System Block Diagrams
20
User
Guide
R E P E AT E R B L O C K D I A G R A M
Figure 4-1 shows a block diagram of a Daniels P25 mixed mode repeater system. The receiver will
receive the incoming FM or C4FM transmission and will automatically detect and demodulate the signal
to an analog or P25 digital signal. The signal is then converted into a digitally sampled signal and then
routed through the analog or P25 digital settings programmed into the receiver. Analog signal settings
may include CTCSS or DCS decoding, de-emphasis and wide or narrowband selection. P25 digital
settings will include NAC and/or TGID decoding. The digitally sampled signal is then split and routed
out of the receiver as both LVDS serial data out the front panel, and analog audio out the subrack /
motherboard. If a P25 digital signal is sent out as analog audio, the signal must fi rst be de-vocoded
before it can be converted to analog audio. An analog or digital COR signal is also routed out the front
panel.
The analog and digital COR signals and LVDS serial data are then routed through the repeater controller
(CI-RC-4L Repeater Controller or CI-RC-4M Multiple Link Controller) and are sent to the transmitter as
analog and digital PTT signals and LVDS serial data.
The transmitter will accept the incoming LVDS serial data and route it through the analog or P25 digital
settings programmed into the transmitter. Analog signal settings may include CTCSS or DCS encoding,
pre-emphasis and wide or narrowband selection. P25 digital settings will include NAC encoding (unless
the receiver is set to a NAC of $F7F to pass the NAC through the repeater). The transmitter will then
modulate the analog or P25 digital signal as either FM or C4FM, based on the analog or digital PTT
input. The analog audio input to the transmitter is not used in a repeater confi guration.
Figure 4-1: P25 Repeater Block Diagram
REPEATER
RECEIVER
REPEATER
TRANSMITTER
REPEATER
CONTROLLER
SUBRACK /
MOTHERBOARD
RF IN
RF OUT
FRONT PANEL
RJ45 CABLE
FRONT PANEL
RJ45 CABLE
ANALOG COR
A / D
DETECT
A
D
CTCSS / DCS
DECODE
DE-EMPHASIS
FILTER
NAC / TGID
DECODE
DE-VOCODER
AUDIO
OUTPUT
(TO SYSTEM
MONITOR SPEAKER)
LVDS
SERIAL
DATA
A / D
SELECT
A
D
CTCSS / DCS
ENCODE
PRE-EMPHASIS
FILTER
NAC
ENCODE
VOCODER
SUBRACK /
MOTHERBOARD
ANALOG PTT
LVDS
SERIAL
DATA
RX TO TX
ENABLE
AUDIO
INPUT
(NOT USED)
FM ANALOG OR
C4FM DIGITAL
FM ANALOG OR
C4FM DIGITAL
DIGITAL COR
DIGITAL PTT
1 KHz TONE
@ 60% MAX. MOD.
= -8.0 dBm
1 KHz TONE
@ -8.0 dBm
= 60% MAX. MOD.
