AES 7085UE2 User Manual

HEC

7085-UE2

PLL SYNTHESIZED (EEPROM)

DATA TRANSCEIVERS

Service Manual

UHF

HERMES ELECTRONICS CO., LTD.

TABLE OF CONTENS

1. SPECIFICATION … … … … … … … … … … … … … … … … … … … … … … … … … ..

2. CONNECTIONS AND OPERATION …… … … … … … … … … … … … … … … 3

3. CIRCUIT DESCRIPTION … … … … … … … … … … … … … … … … … … … … ..4-12

4. PERFORMANCE TEST AND ALIGNMENT … … … … … … … … … … … 12

5. TEST EQUIPMENT CONFIGURATION … … … … … … … … … … … … … 13

6. TRANSMITTER PERFORMANCE TEST … … … … … . … … … … … … … … … .14-16

7. TROUBLESHOOTING … … … … … … … … … … … … … … … … … … … … … … ..17-19

9. PARTS LIST … … … … … … … … … … … … … … … … … … … … … … … … … … ..20-28

8. PROGRAMMER INSTRUCTION … ….. …… … … … … … … … … … … … … … .29-34

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10. PRINT CIRCUIT BOARD LAYOUT … …… … … … … … … … … … … … … … … 35

11. PARTS ASSEMBLY … … … . … … … … … … … … … … … … … … … … … … … … .36

12. BLOCK DIAGRAM … …. … … … … … … … … … … … … … … … … … … … … … 37

13. SCHEMATICS DIAGRAM … … … … … … … … … … … … … … … … … … … … … 38

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1. SPECIFICATION

GENERAL SPECIFICATIONS

POWER SOURCE … … … … … … … … … … … … … … … +12VD.C. nominal(+10.8 to +15.6V )
TEMPERATURE RANGE
STORAGE … … … … … … … … … … … … … … … .80℃ maximum -40℃ min.
25℃ nominal
OPERATING … … … … … … … … … … … … … … .70℃ maximum -20℃ min.
ANTENNA IMPEDANCE … … … … … … … … … … … … ...50Ω
FREQUENCY CONTROL … … … … … … … … … … … … … ...PLL SYNTHESISER
FREQUENCIES OF OPERATION … … … … … … … … … ..450-470MHZ
FREQUENCY TOLERANCE AND STABILITY … … … … ±1.5PPM
HIGH HUMIDITY … … … … … … … … … … … … … … … … .90﹪
CHANNEL CAPABILITY … … … … … … … … … … … … … .1
NOMINAL DIMENSIONS … … … … … … … … … … … … … .134 ㎜(L)X60 ㎜(W)X20 ㎜(H)
WEIGHT … … … … … … … … … … … … … … … … … … … … … .136g

RADIO DATA TRANSCEIVER NOMINAL PERFORMANCE

PERFORMANCE SPECIFICATIONS … … … … … … … … … ...ECC
RF OUTPUT POWER … … … … … … … … … … … … … … ..2W~3W
MODULATION TYPE … … … … … … … … … … … … … … … .FM
INTERMEDIATE FREQUENICES … … … … … … … … … … .21.4 MHZ
455 KHZ
CHANNEL SPACING … … … … … … … … … … … … … … … .12.5KHZ
TRANSMIT ATTACK TIME … … … … … … … … … … ＜25 mS
CURRENT CONSUMPTION
TRANSMIT … … … … … … … … … … … … .700mA@3W
RECEIVE … … … … … … … … … … … … ..85mA

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EXTERNAL CONNECTIONS

PIN

FUNCTION

TYPE

RANGE

DESCRIPTION

1-

50Ω BNC SOCKET

2-

9 WAY 〝 D 〞TYPE PLUG(J501)

2. CONNECTIONS AND OPERATION

D-TYPE INTERCONNECTIONS

J501-1 DATA_IN ANALOGUE 106mV EXTERNAL MODULATION INPUT
J501-2 DATA_OUT ANALOGUE 250~350mV RECEIVER AF OUTPUT
J501-3 PTT INPUT 0V/+5V TRANSMIT ENABLE
J501-4 GND GND 0V GND
J501-5 B+ V+ +13.8V POWER SUPPLY
J501-6 CDS OUTPUT OPEN/SHORT RF CARRIER DETECT
J501-7 NC
J501-8
J501-9 PGM_ENB INPUT 0V/5V PROGRAMMING ENABLE

PGM_DATA

INPUT 0V/NC PROGRAMMER DATA INPUT

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3. CIRCUIT DESCRIPTION

TRANSMITTER

The transmitter is comprised of:

• Audio amplifier connections from J1 pin 1

• Frequency Synthesizer

• Transmitter

• Automatic Power Control

Audio frequency connections
Processed data from the IC201 is applied to the VCO via R316

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:

• 12.8 MHZ Tcxo

• Voltage Controlled Oscillator (VCO) module

• Charge Pump and Loop Filter

• PLL Frequency Synthesizer

• Dual Modulus Prescaler

With data received from the EEPROM (IC5) the frequency synthesizer circuit controls and

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PLL Synthesizer

The PLL synthesizer circuit is common to both the transmitter and receiver,
The synthesizer comprises:

Data

RF Out

TCXO

IC1

PLL

TX OR RX
VCO

DC
Regulator

Loop Filter

Charge Pump

12.8 MHZ TCXO
X1 is VCTCXO, which provide stable oscillator of 12.8 MHZ to PLL IC.
Frequency adjustment is provided by VR1.

.Voltage controlled oscillator module(VCO)

The module produces carrier frequencies during transmit and local oscillator frequencies
During receive.

The module contains one VCO and three outputs. One for producing carrier frequencies during
Transmit and one for producing the local oscillator frequency during receive and the other
Output is for PLL IC(IC1) Fin.

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The module also has Rx and TX powerline filters.

Transistor Q301 is configured as a 5v power supply ripple filter. The filter reduces the
noise on the carrier and local oscillator signals.

The VCO comprises Q302, Coil L304, and varactor D301 D304 and is configured
as a Colpits oscillator. D301 D304 produces a change in frequency with a change in DC voltage
and is controlled by the tuning voltage signal present at the cathode. The local oscillator
programmable dividers. DATA is received by IC1 at pin 10 from pin 11of IC3.

The RF signal at the collector of Q302 is applied to an amplifier/buffer Q305.The amplified
Signal from Q305 passes to the prescaler ,IC1 pin8 .The RF signal at the collector of Q302 also
Drives the cascode amplifier/buffer formed by Q304 .

When D201 is forward biased (TX ON) , carrier frequencies at the collector of Q304 pass to the
Power amplifier and harmonic filter. When D303 is forward biased (RX) , local oscillator
Frequencies at the collector of Q304 pass to the first mixer . VC1 adjusts the tuning

RX and TX power line filters

VCO

Voltage of the VCO to the correct operating point.

The reference frequency from the TCXO, at 12.8 MHZ , is connected to pin 1 of IC1(MB1504)

REFDIV divides the 12.8 MHz to produce a reference frequency (Fr) of 5 or 6. 25 kHz
dependent upon channel spacing selected. VARDIV divides the prescaled VCO frequency
to produce a variable frequency (Fv). Fv and Fr are fed to the phase detector.

When Fv=Fr, the phase detector output (pins 15 and 16,IC1) produces narrow negative pulses
And Fv and Fr pulse widths are identical. When Fv〉Fr pin 15 (V) pulses negative with pin 16
(R) remaining high. When Fv〈Fr pin 16 (R) pulses negative with pin 15(V) remaining high.
The signal at pin 15 and 16 is smoothed the loop filter and applied to the VCO.

PLL IC

Phase detector

The out-of-lock detector produces a series of logic level pulses when the loop is out of lock at
pin 7 of IC1.The pulses at pin 7 of IC1 are buffered by Q6 and then integrated by R17 and
C19. The product of the integrating circuit is fed to Base of Q201.

Out-of-lock detector

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Charge Pump and Loop Filter

Transistors Q2,Q4,Q10 , and associated resistors and capacitors form the charge pump and loop
Filter . The phase detector output from IC1 pins 15 and 16 are combined by the charge pump to
Produce a 0 to 8V tuning voltage signal.

The signal is filtered by the loop filter (R13,C15 and C20) to remove any residual reference
Frequency harmonics from the signal.. After filtering the signal is applied to the voltage controlled
Oscillator module.

DC REGULATOR

The DC Regulator IC2, converts the +13.6 V to a 8V supply . This is used to provide the
Tuning voltage for the VCO . A wide voltage range is required to allow for the wideband operation
Of the radio .

Dual modulus prescaler

The prescaler divides the VCO frequency by 64 or 65.

Transmitter
The transmitter comprises:

VCO Buffer PA Module
Amp

ANTENNA

RF LPF

Automatic
Power Control

SWITCH

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Buffer
When the radio is in transmit mode the diode D201 is forward biases enabling the

modulated RF signal from the VCO to pass to the buffer/pre-amplifier Q204 and
associated components.

The output signal is passed from Q204 to Q205 via a matching network consisting of

Inductor L201 and C208.

PA module

The signal is then amplified for transmission by Q207, which is a power amplifier module.

Low pass filter

The amplified RF signal is passed through the stripline coupler and is fed to the

harmonic low pass filter, comprising L213 to L214 and C232-C234 and then to the antenna
connector (ANT).

Antenna Switch

When transmitting, the diodes D205 are forward biased, the RF pass to the antenna.
D205 is shorted to ground which makes L212 look open circuit (1/4 wave

tuned stub). This prevents the TX signal from passing to the receiver stage.

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Receiver

The receiver comprises:

SAW FILTER&
Amp

ANTENNA
SWITCH

Rx
VCO

First Mixer

IF Filter

IF Amp

Second
Mixer

Local
Oscillator

IF
Filter

Data Out

Audio Filter

FM
Limiter­Discnminator

Squelch
Circuit

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Antenna Switch
In receive, the diode D205 are reverse biased. L212 is now in circuit, passing

the signal from the antenna to the SAW filter of F101.

SAW FILTER

The receiver signal is routed to pin 4 of the F101. It passes through the
band pass filter .

The input signal is coupled to the base of Q101 which serves as an RF amplifier.
The output of Q101 is then coupled to the first mixer.

First Mixer
Q102, 2-pole crystal filters XF1 and coils L103 and C120 form the First Mixer

and First IF Filter.

The RF signal, from the SAW filter and amplifier Q101 is
applied to the VCO local oscillator signal to make mixer.

The difference frequency of 21.4 MHz is taken from Q102 and is filtered by the crystal
filters XF1. The tuned circuits L103 and C120 and associated components provide
matching of the crystal filters to ensure a good pass-band response and selectivity.

The IF signal is amplified by Q104 and passed to the FM Detector IC.

Second mixer, Second IF, FM detector
The output of the IF amplifier is fed into the narrowband FM IF Integrated Circuit,

IC101 (MC3361). This is a single conversion FM receiver which contains the second
mixer, second IF amplifier, and FM detector.

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Crystal X101,connected to pin 1 of IC101, determines the second local oscillator frequency.
In this case the crystal has a frequency of 20.945MHz. The first IF signal is applied to
the mixer and resultant frequency of 455KHz, is the difference between the IF signal
and second local oscillator.

The 455KHz IF signal is output from pin 3 and is applied to a 455KHz band-pass filter CF1.

The output of CF1is passed via pin 5 to a high gain IF amplifier coupled to the
adjustable quadrature detector T2.Any detected signal is produced at pin 9 of
IC101 and applied to the Receiver Audio Circuit and the Mute (Squelch) Circuit.

Squelch ( MUTE ) Circuit

Any noise signal is amplified by IC101 internal noise

Signal is applied to pin10 of IC101. The squelch trigger output (pin 12,IC101) is applied to the
pin 6 of J1.

When noise is present, the voltage at pin 12 of IC101 is exceeds than 0.7V. The squelch trigger

output is open, It’s make pin 6 of J1 open state.

When no noise is
Is HI voltage. This make pin 6 of J1 short state.

VR101 is set to tuning squelch when 25khz channel space is present.

Carrier Detect
A Carrier Detect ( MUTE DETECT ) output is available on pin 6 of J1 .

AF Output Low Pass Filter
A low pass filter formed by R108 and C110 removes any extraneous 455kHz energy

from the AF output of the FM receiver chip (pin 9 of IC101).

present, the

voltage at pin 12 of IC101 less 0.7v and pin 13 of IC101

amplifier .

The filtered signal is passed to pin 2 of J1.

Microcontroller

The PIC16C57C04 microcontroller IC controls the programmable features and frequency synthesizer
Data.

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