Navman VHF 7100 User manual

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THEORY OF OPERATION
VHF7100/VHF7000 (For NAVMAN)
November 28, 2003
This PLL controlled VHF marine mobile transceiver provides an accurate and stable multi-channel
operation.
The transceiver consists of 12 main sections
Transmitting stage
!" Receiving stage
!" Local oscillator PLL (Phase Lock Loop) Circuit
!" Memory backup
!" Low voltage detection
!" Large LCD
!" Local/distance circuit
!" 2nd receiver. (only VHF7100EC)
!" wx alert circuit [only VHF7100USA]
!" PC program
!" DSC Feature [only VHF7000ROW without]
!" GPS Message [only VHF7000ROW without]
!" ATIS Feature. (only VHF7100EC)
!" Transmitter Stage
The audio is picked up from the internal Mic. The audio signal is then amplified by Audio Amplifier,
IC205C [NJM3403AM], IC205 B [NJM3403AM] and filtered by a low pass filter IC10C [NJM3403AM]),
IC10D [NJM3403AM]). The audio that is adjusted by VR3 to obtain a suitable RF frequency-deviation,
modulates the carrier of VCO, through Varicap (VD302).
The modulated signal output from the VCO is pre-amplified by Q2, and IC1 (RA35H1516M-01). When the
supply voltage is 13.8V, this signal will be amplified up to 1W or 25W. The signal is filtered by low-pass
filter circuit of which consists of L1, L2, L4, C1, C2, C3, C5, C6. C14, C47 and C62.These low pass filters
are necessary to suppress the second and the third harmonics as higher. The signal is then fed into the
antenna input and radiated out. The signal is also fed into another path consisting of C9, C10, D3, D4 for
sampling, and is converted into a direct current voltage for the Automatic Power Control (APC) circuit
IC12 (NJM2904M) Q5, Q14, Q15,Q24 to control the voltage of IC1 Pin 2 to maintain the output power
stability. Q15 is used control Hi/Lo power
When the unit is transmitting, the channel control voltage is added to the TX VCO varicap VD306. The
capacitance of VD302 is varied following the audio signal, therefore the carrier is modulated to form the
modulated signal.
!" Receiver
The receiver uses a double frequency super-heterodyne circuit. The first Immediate Frequency (IF) is
21.4 MHz and the second is 455 KHz.
The RF signal is received by the antenna, and passes through a low-pass filter network L1, L2, L3, L9, C1,
C2, C3, C5, C6. C14, C47 and C62 to filter out unwanted signal. the received RF signal then passes
through a high RF transformer L10 and is amplified by RF amplifier Q9. L11, L12, L13, C15, C18, C20
form the band pass filter. The RF signal then is mixed with the local oscillation frequency by the mixer

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D22, D23. The first IF (Immediate Frequency) 21.4 MHz is produced. This IF is passed through a coil T2
and a pair of crystal filter F1, F2 to further filter out other unwanted signals. The first IF then is amplified
by Q11 and the IF amplifier IC7 (BA4116FN). (IC7 is an integrated IF amplifier which consists of a local
oscillator, a demodulator, a second mixer, squelch control circuit, and IF amplifier). The 21.4 MHz IF then
is mixed here with second mixer and converted into 2nd Immediate Frequency (IF) 455 kHz. The 2nd IF
passes through a ceramic filter F4 to filter out the residue unwanted signal at pin 5 of IC7 (BA4416FN)
output this final IF signal and The demodulated AF signal is output at pin 9 of IC7 (BA4416FN).
The demodulated AF signal is amplified by IC8B. the amplified audio then passes through a volume
control VR201 through de-emphasis circuit feeding IC10A, IC10B.and finally amplified by Audio amplifier
IC11 (LA4629) and heard in the speaker.
The squelch control signal also produced by IC7 (BA4116FN), the rectified noise signal is output by Pin
14 of the IC7 then signal is amplified by IC8A. Pass through the network by composition of R45 R38 R44
and C171 sends the digital squelch control signal to the MCU to mute the audio speaker path and to
indicate the RX station on LCD. R214.R217 and VR203 form a variable resistor, which correspond to the
squelch level.
!" Local oscillator PLL (Phase Lock Loop) Circuit:
The receiver and transmitter both share the same PLL (Phase Lock Loop) Circuitry to produce the carrier
frequency or the receiver local oscillation frequency. The local oscillator consists of a fundamental
frequency oscillator Q301 and A phase Lock Loop (PLL) IC16 (TB31202) When Rx 5Vvoltage is supply,
the VCO will produce receiver local oscillator frequency. The high stability frequency is determined by
crystal X2 (20.950 MHz) and as the PLL reference oscillator. This signal is frequency-divided by IC16 and
a 12.5 kHz signal is produced. When the VCO frequency applied to IC16 pin1 and frequency-divided by
IC2 produces a frequency comparable to 12.5 kHz, PLL IC pin 3 will output a PD voltage to control the
VCO. When these two frequencies are matched, a constant control voltage is output from PLL to lock
VCO in desired frequency. Otherwise the PLL IC pin 4 will also output a unlock indication to MCU to
indicate that the PLL is in the frequency unlock state.
!" Memory Backup
IC201 is an EEPROM AT24C64, which acts as a memory backup for the working channel code and the
system parameters. Every time when the unit is switched on, the MCU will reset the system, clear the
RAM, and recall the memory from the EEPROM to refresh the RAM in MCU IC203.
!" Low Voltage Detection
The battery voltage divided byR250 and R251 through R254 is input to IC203 for voltage level detection.
If the battery voltage drops below 9.5 V, LCD will indicate the battery is in low state.
!" Local/distance circuit
Local/distance circuits are composed of Q16,R195,R94,C125.L17,D17,R93. When local SW is on high
level, receiver sensitive is high otherwise is on low.
!" Wx alert circuit
The 1050Hz tone of receiver through IC6A composed band-pass filter and IC6B amplifier form square
wave signal. To fed IC203 pin 97produce weather alert.
!" Large LCD
All message through series bus from MCU to display driver IC204 and will be displayed through a
1.5″1″×1″in 4×12 characters dot matrix LCD display.

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!" 2nd receiver.
2nd receiver circuit is as figure. RF input is from C101 (‘0.5PF) of main PCB, the received RF signal then
passes through a high RF transformer L505 and is amplified by RF amplifier Q501 L506, L507, L508,
C15, C18, C20 form the band pass filter. then passes through a high RF transformer L509 is mixed with
the first local oscillation frequency by the mixer D501,D502.D503.D504. The first IF (Immediate
Frequency) 17.9 MHz is produced. This IF signal is passed through a transformer coil L510 and a pair of
crystal filter F1, F2 to further filter. The first IF then is amplified by Q503 and the IF amplifier IC501
(DBL5018). IC501 is an integrated IF amplifier which consists of a 2nd local oscillator (18.355Mhz),a
demodulator, a second mixer, squelch control circuit, and IF amplifier circuits). The 17.9MHz IF then is
mixed here with second mixer and converted into 2nd Immediate Frequency (IF) 455 kHz. the 2nd IF
passes through a ceramic filter F503 to filter out the residue unwanted signal at pin 5 of IC501 (DBL5018)
output this final IF signal and The demodulated FSK signal is output at pin 9 of IC501 (DBL5018) through
R517 C543 pass J501.J4 fed in IC15 pin 13 of the main PCB.
The squelch control is also controlled by IC501 (DBL5018). The audio signal passes through the low
pass filter R514, R515, C541 and IC501 (DBL5018) internal squelch control R516, and C542 that form as
a squelch amplifier to produce a squelch signal (noise) from pin11 of IC501 (DBL5018) output , this signal
is then amplified by Q505 and regulated by D505 to produce a direct current voltage as a control voltage
then it is fed throughR526and pin14 to IC501 (DBL5018) from pin13 output the busy signal.
!" PC Program
J203 on CPU is connected with the outside cabinet through a cable with a round pin8 plug. Software
upgrade and clone can be functioned when an exclusive interface control box is connected with RS-232
interface of computer.
When the light on control box is green, J203 pin3 is high level(5v), CPU programming is performed, and
the software is upgraded.
When the light on control box is red, clone function is performed.
!" DSC Feature
DSC TX Encoded by MCU IC203, through RP1, R237, R234, produces D/A convert, and IC205D low
pass filter forms FSK signal. This signal is amplified by IC205A and filtered by IC10C, IC10D to
modulate VCO frequency from the DSC signal transmit output.
ON the VHF7100 USA, DSC signal is received and demodulated by IC7.the Demodulated signal is sent
into pin12 of IC601, from pin 14 of IC601 output , then the signal passes then through IC6C high-pass
filter and IC6D low-pass filter form FSK signal. This FSK is signal decoded by IC609. The DSC is
restored by IC203 [MCU] with RX data from IC9 pin7. While the VHF7100 EC
While the VHF7100 EC , DSC signal is from 2nd receiver. It be Send to IC15 pin13 on the main PCB.
!" ATIS Feature
ATIS encoded by MCU IC203, through RP1, R237, R234, produces D/A conversion, and IC205D low
pass filter forms FSK signal. Through the attenuation be composed of R215, R218, R274 and Q204 This
signal is amplified by IC205A and filtered by IC10C, IC10D to modulate VCO frequency forming the ATIS
signal transmit output.
ATIS signal is received and demodulated by IC7. Demodulated signal is sent into pin12 of IC601, from
pin 14 of IC601 output .the signal passes through IC6C high-pass filter and IC6D low-pass filter to get
ATIS FSK signal and filter out residual unwanted signals. This FSK is signal decoded by IC609. The
ATIS is restored and processed by MCU IC203 with RX data from pin7 of IC609. Be formed control signal
to production about 100ms squelch to mute audio speak path.
!" GPS Message
External GPS Message is input to MCU through phototransistor IC207 LCD will display the machine
current location and time message in idle state.

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ALIGNMENT AND ADJUSTMENT
This transceiver is completely aligned at the factory and does not require any adjustments for installation.
However it is considered as good practice to verify that none of the adjustments are changed.
Do not adjust any circuitry in this radiotelephone unless you understand the circuit operation and have
experience in adjusting radiotelephone. Tampering with the radiotelephone may upset the alignment and
lower its performance.
Test Equipment Required:
!" Regulated DC power supply, 15V,7A
!" Audio signal generator,10Hz~3kHz
!" Digital multimeter
!" Deviation meter
!" Frequency counter,0~500MHz high impedance
!" Oscilloscope
!" RF power meter, ≥30W
!" High frequency standard generator,>500MHz
!" Tracking generator,>500MHz
!" Distortion analyzer
!" Audio level meter
!" T-coupler
!" Alignment drivers, etc. ADJUSTMENT PROCEDURE
Step Item Adjustment Procedure
1 TX Frequency VC2 Adjust VC2 to obtain demanded TX frequency.
2 TX Power Hi VR5 Adjust VR5 to obtain demanded TX power 23±2W.
3 TX Power Lo VR6 Adjust VR6 to obtain demanded TX power 0.8±0.1 W.
4 TX. Dev. VR3 1. Inject an audio frequency (AF) -20dBm.
2. Adjust VR3 to obtain maximum TX deviation ≤5kHz.
3. Check MIC modulation sensitivity, which should be
2.5~10mV.
5 RX L10,L11,L12,
L13,L14,T1,T2
1. Check RX sensitivity if it is normal.
2. Adjust L10, L11, L12, and L13 to obtain Best Frequency
response.
3. Adjust L14,T1 and T2 to obtain Best RX sensitivity

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TROUBLE SHOOTING
Before troubleshooting, prepare your unit as follows:
!" Turn volume control fully clockwise so that it is all the way up.
!" Install the batteries onto your unit.
Item Symptom Cause/Remedy
1 Unit is not able to turn on. !" Check the power voltage and power switch.
!" Check to see if regulator IC8 defective.
2 No sound with AF signal
applied to pin 6 of IC6.
!" Check to see if IC1 and /or associated components is
Defective.
!" Check to see if speaker on control circuit VR201, IC10A,
IC10B, is defective.
3 Squelch circuit inoperative. !" Check to see if VR203 is defective.
!" Check to see if IC4 is defective.
4 No receiver (RX) !" Check to see if IC11 is defective.
!" Check to see if IC4 audio output at pin 9 is defective.
!" Check Q12.
!" Check 21.6MHz output of first mixer Q10.
!" Check 21.6MHz output of crystal filters F1, F2.
!" Check 21.6MHz output of first IF amplifier Q11.
!" Check 455kHz signal from ceramic filter F3.
!" Check to see if VCO circuit is defective.
!" Check to see MCU is defective.
5 Low receiver sensitivity !" Check to see if antenna is bad connecting.
!" Check to see if the output from Q9, Q10, Q11 and F1 F2 is
defective.
6 No transmission (TX) !" Check to see if the PTT switch is defective.
!" Check to see if Q13 is defective.
!" Check to see if power transmit circuit Q1, Q2, Q3 are
Defective.
!" Check to see if VCO circuit is defective.
!" Check PLL control voltage if it reads 1.2±0.3V at 156.05MHz.
7 Poor or no modulation !" Check to see if the microphone or MIC jack is defective.
!" Check to see if IC205 and/or its associated components are
defective.
8 Deviation of transmit frequency !" Check the frequency of 12.8MHz crystal X3.
!" Adjust VC2 and verify the transmit frequency.

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DISASSEMBLY INSTRUCTIONS
1. Rotate counterclockwise volume knob to OFF position.
2. Pull out all external wires (GPS, SP, POWER).
3. Unscrew 2 mounting nuts.
4. Remove the main radio from the mounting bracket.
5. Unscrew the four screws of hand MIC.
6. Separate the front cabinet and bottom cabinet of the hand MIC.
7. Unscrew 6 screws for the bottom cabinet of the main unit.
8. Separate the front cabinet and bottom cabinet of the main unit.
9. Unscrew the mounting screw of the upper shielding case.
10. Remove the upper shielding case.
11. Unscrew the mounting screw of the lower shielding case.
12. Remove the lower shielding case.