Maxon Telecom SM-2000 service manual Squelch Adjustment, Automatic Power Adjustment

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MAXON SM-2000 MOBILE

SM-2150/VHF ALIGNMENT PROCEDURE

Squelch Adjustment

1.Select a receiver channel that is programmed for narrow band (12.5 kHz) operation.

2.Set the RF signal generator to the receiver frequency. Set the AF modulation signal to 1 kHz at 1.5k deviation.

3.Adjust the RF output level of the RF signal generator until the 1 kHz signal is heard.

4.Adjust the RF signal to the level desired for squelch sensitivity as you monitor SINAD. This is usually 8dB to 12dB SINAD.

5.On the main board adjust RV103 until the squelch is just unmuted (open)

6.Switch off the RF generator (squelch should close).

7.Switch on the RF generator. Squelch should open at the SINAD point where RV103 was adjusted. This completes the narrow band adjustment.

8.Select a receiver channel that is programmed for wide band operation (25 kHz).

9.Set the RF signal generator to the receiver frequency. Set the AF modulation signal to 1 kHz at 3k deviation.

10.Adjust the RF output level of the RF signal generator until the 1 kHz signal is heard.

11.Adjust the RF signal to the level desired for squelch sensitivity as you monitor SINAD. This is usually 8dB to 12dB SINAD.

12.On the main board adjust RV102 until the squelch is just unmuted (open).

13.Switch off the RF generator (squelch should close).

14.Switch on the RF generator. Squelch should open at the SINAD point where RV102 was adjusted.

15.Disconnect the test equipment.

Automatic Power Adjustment

Continuous transmit periods longer than 5 minutes are to be avoided.

1.Connect the antenna output to a RF power meter or service monitor.

2.Set the PTT switch to the ON position.

3.Adjust the variable resistor RV104 to give the appropriate transmit power. Normally this is 25watts.

4.Set the PTT switch to the OFF position.

5.Select a channel programmed to low transmit power.

6.Set PTT to ON and adjust RV105 for desired low power.

7.Set PTT to OFF.

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December 98

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Contents SM-2000 Page Table of Contents Maxon SM-2000 MobilePCB Layouts Schematics and Block DiagramsSM-2000 Exploded View Transceiver Nominal Performance SpecificationsGeneral Band Operational BandwidthTransmitter Specfications SUB Audible Tones DCS TX Tone Modulation CharacteristicsReceiver RX Tone Demodulation Characteristics AccessoriesSubaudible tones CTCSS/DCS Reliability AnalysisIntroduction Unpacking Information Check the carton carefully for the following itemsGeneral Description Description of Controls Description of ControlsSM-2000 Rear Panel Theory of Operation Digital CircuitryCTCSS/DCS Decode Circuits CTCSS/DCS Encoder CircuitEeprom PLL RF Section SM-2150/VHF RX VCO TX VCOOut of Lock Detector PrescalerReceiver RF AmplifierReceiver Audio Circuit Low Pass FilterAudio Amplifier Noise Detect Circuit SQ BoardUHF Transmitter RF Section SM-2450/UHFFrequency Synthesizer Circuit First Mixer Voltage Controlled Oscillator CircuitSecond Oscillator- Mixer- Limiter and FM Detector Squelch Mute Circuit Squelch Noise Band Pass FilterNoise Detector Speaker Audio AmplifierTest Setup Transmit TestsSM-2150/VHF Alignment Procedure PLL AlignmentDiscriminator Tuning Receiver Alignment RFSquelch Adjustment Automatic Power AdjustmentCTCSS/DCS Deviation Adjustment Modulation Deviation AdjustmentAlignment Points Diagram SM-2150/VHF SM-2450/UHF Alignment Procedure Page-28 December ∙ Note Release the PTT button when changing channels Page-30 December Alignment Points Diagram SM-2450/UHF Surface Mount Components Component ReplacementSurface Mount Removal Surface Mount Component Replacement Surface Mounted Integrated Circuit ReplacementParts List Common to SM-2000 REF # DescriptionDigital Parts Common on Both VHF & UHF Digital Section Band Chart REF # Description FRONT-END PCB Assembly Main Board PartsPage-38 December Page-39 December Page-40 December Page-41 December SM-2450A UHF Band SM-2450C UHF Band SM-2450D UHF Band Band Chart SM-2450E UHF BandPage-44 December Page-45 December Page-46 December Page-47 December Component Pinout Page-49 December Page-50 December Voltage Charts SM-2150/VHF IC409Page-52 December Transistor Voltage Chart Voltage Charts SM-2450/UHF IC404 Page-56 December Trouble Shooting Chart SM-2000 Status Indications & Audible TonesPage-58 December Replacement Module Schematics MMBV109MA-4472 Microphone Schematic Page-61- December Page-62- December Page-63- December Page-64- December SW5 SM-2000 Control HeadSM-2150/VHF Main Board Assy Page-66 DecemberSM-2450/UHF Main Board Assy FrontSM-2000 SM-2150/VHF Exploded View Parts List Intentionally Left Blank