AES 7880LC2B Users Manual
52-7880LC2B
UHF
DATA TRANSCEIVERS
PLL SYNTHESIZED (EEPROM)
Service Manual
HERMES ELECTRONICS CO., LTD.
1. SPECIFICATION …………………………………………………………………..
2. CONNECTIONS AND OPERATION DESCRIPTION……………………3-4
3. CIRCUIT DESCRIPTION ……………………………………………………..5-7
4. PERFORMANCE TEST AND ALIGNMENT……………………………8
5. TEST EQUIPMENT CONFIGURATION …………………………………9
6. TRANSMITTER PERFORMANCE TEST …………….……………………….10-12
7. PARTS LIST ……………………………………………………………………..13-16
TABLE OF CONTENS
2
8. PROGRAMMER INSTRUCTION……..……………………………………….17-21
9. PRINT CIRCUIT BOARD LAYOUT……………………………………………..22-24
10. PARTS ASSEMBLY ……….…………………………………………………….25
11. BLOCK DIAGRAM …….………………………………………………………26
12. SCHEMATICS DIAGRAM………………………………………………………27
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1. SPECIFICATION
GENERAL SPECIFICATIONS
POWER SOURCE ……………………………………….13.80VD.C.
TEMPERATURE RANGE
STORAGE ……………………………………….80℃ maximum -40℃ min,25℃ nominal
OPERATING …………………………………….70℃ maximum -20℃ min.
ANTENNA IMPEDANCE ………………………………...50Ω
FREQUENCIES OF OPERATION ………………………..406-430MHZ,450-470MHZ
FREQUENCY TOLERANCE AND STABILITY …………±1.5PPM
CHANNEL CAPABILITY ………………………………….1
NOMINAL DIMENSIONS ………………………………….107 ㎜(L)X 54 ㎜(W)X 32 ㎜(H)
WEIGHT ……………………………………………………….101g
RADIO DATA TRANSMITTER PERFORMANCE SPECIFICATION
RF OUTPUT POWER ……………………………………..2.5W
MODULATION TYPE ……………………………………….FM
CHANNEL SPACING ……………………………………….25KHZ/12.5KHZ/6.25KHZ
DEVIATION (25KHZ CH SPACING)………………………….3.35 KHZ@106mVrms input
MAX. DEVIATION…………For 12.5 kHz channel spacing, Peak deviation is not greater than 2.5 kHz.
…………For 25 kHz channel spacing, Peak deviation is not greater than 5 kHz.
TRANSMIT ATTACK TIME …………………………＜25 mS
CURRENT CONSUMPTION ……………………………….1500mA@2.5W
RADIO DATA RECEIVER PERFORMANCE SPECIFICATION
SENSITIVITY………………………………………..minimum 12dB SINAD @0.35uV
QUIETING………………………………………….. minimum 20dB @0.5uV no modulation
AUDIO POWER OUTPUT…………………………250mV~500mV rms @600 ohms load
AUDIO DISTORTION………………………………less than 5%@ -47dBm
CARRIER DETECT OFF…………………………….> -117dBm
CARRIER DETECT ON……………………………..< -120dBm
HUM AND NOISE……………………………………45dB
SELECTIVITY………………………………………..70 dB
SPURIOUS RESPONSE………………………………70 dB
CURRENT CONSUMPTION ………………………60mA
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EXTERNAL CONNECTIONS
PIN
FUNCTION
TYPE
RANGE
DESCRIPTION
J2-1
DATA_IN
ANALOGUE
106mV
EXTERNAL MODULATION INPUT
J2-2
DATA_OUT
ANALOGUE
250~350mV
RECEIVER AF OUTPUT
J2-3
PTT
INPUT
0V/+5V
TRANSMIT ENABLE
J2-4
GND
GND
0V
GND
J2-5
B+
V+
+13.8V
POWER SUPPLY
J2-6
CDS
OUTPUT
OPEN/SHORT
RF CARRIER DETECT
J2-7
NC
J2-8
PGM_DATA
INPUT
0V/NC
PROGRAMMER DATA INPUT
J2-9
PGM_ENB
INPUT
0V/5V
PROGRAMMING ENABLE
1. -
50Ω BNC SOCKET
2. - 9 WAY 〝 D 〞TYPE PLUG(J2)
2. CONNECTIONS AND OPERATION
D-TYPE INTERCONNECTIONS
PAGE3
U4(52-7880LC2) CONNECTIONS
PIN
FUNCTION
TYPE
RANGE
DESCRIPTION
JP1-1
DATA_IN
ANALOGUE
106mV
EXTERNAL MODULATION INPUT
JP1-2
DATA_OUT
ANALOGUE
250~350mV
RECEIVER AF OUTPUT
JP1-3
PTT
INPUT
0V/+3.3V
TRANSMIT ENABLE
JP1-4
GND
GND
0V
GND
JP1-5
B+
V+
+6.0V
POWER SUPPLY
JP1-6
CDS
OUTPUT
OPEN/SHORT
RF CARRIER DETECT
JP1-7
PGM_ENB
INPUT
0V/3.3V
PROGRAMMING ENABLE
JP1-8
PGM_DATA
INPUT
0V/NC
PROGRAMMER DATA INPUT
JP1-9
PIN
FUNCTION
TYPE
RANGE
DESCRIPTION
JP2-1
Channel 1
DIGITAL
0V/+3.3V
Channel select pin
JP2-2
Channel 2
DIGITAL
0V/+3.3V
Channel select pin
JP2-3
Channel 4
DIGITAL
0V/+3.3V
Channel select pin
JP2-4
Channel 8
DIGITAL
0V/+3.3V
Channel select pin
JP2-5
GND
GND
0V
GND
JP2-6
MCLR
I
0V/+3.3V
Programming MCU software
JP2-7
PGC
I/O
0V/3.3V
Programming MCU software
JP2-8
PGD
I/O
0V/+3.3V
Programming MCU software
JP2-9
VCC
3.3V
3.3V
VCC
CONNECTIONS AND OPERATION
PAGE4
3. CIRCUIT DESCRIPTION
TRANSMITTER
The transmitter is comprised of:
• Audio frequency connections from JP1 pin 1
• Frequency Synthesizer
• Transmitter
Audio frequency connections
In the TX path , audio signal can be send into the chip RDA1846 through AC coupling capacitors.
Frequency synthesizer circuit
Produces the RF carrier frequency for the transmitter during transmit and the local oscillator
frequency for the receiver. The frequency synthesizer circuit is comprised of:
Synthesizer
The U1 (RDA1846) generates the local oscillator and transmitter signal . all building blocks are
fully integrated without any external components. Frequency can be programmed through the serial
interface by the MCU (U3)
26 MHZ TCXO
X1 is VCTCXO, which provide stable oscillator of 26 MHZ to U1.
Frequency adjustment is provided by VR1.
With data received from the EEPROM (U3) the frequency synthesizer circuit controls and
DC REGULATOR
The DC Regulator U4, converts the +6.0 V to a 3.3 V supply . This is used to provide the MCU and U1.
PAGE5
RF LPF
ANTENNA
SWITCH
Power Control
Transmitter
The transmitter comprises:
PA Buffer PA Module
Amp
Buffer
When the radio is in transmit mode the U1 is generated RF signal pass to the buffer/pre-amplifier Q1
and Q2 associated components.
PA module
The Q2 output signal is passed to Q3 via a matching network consisting of Inductor L5 , L15 and C32
and C34. Q3 is power amplifier .
Low pass filter
The amplified RF signal is passed through the stripline coupler and is fed to the
harmonic low pass filter, comprising L11, L12, L17 and C46 , C47, C48 and C58 and then to the
antenna connector (J1).
Antenna Switch
When transmitting, the diodes D3 are forward biased, the RF pass to the antenna.
D4 is shorted to ground which makes L13 look open circuit (1/4 wave
tuned stub). This prevents the TX signal from passing to the receiver stage.
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