EFJohnson 761X UHF Adjustments CONT’D Receiver Adjustments UHF Models, Bandpass Filter Adjust

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ADJUSTMENT PROCEDURE

UHF ADJUSTMENTS (CONT’D)

6.8 RECEIVER ADJUSTMENTS (UHF MODELS)

6.8.1 BANDPASS FILTER ADJUST

1.Select the channel on the low end of the band (Test Ch. 1).

2.Connect an RF signal generator to the antenna jack. Set the output for the channel frequency at a level of 3.2 µV (–97 dBm), modulated with 1 kHz at the following deviation:

Wideband (25 kHz) Models - 3.5 kHz Narrowband (12.5 kHz) Models - 1.75 kHz

3.Adjust the filters automatically or manually as follows:

Automatic Adjustment Method 1

(Adjusts all filters)

a.Select “BPF T1” on the screen and adjust for “0”. Repeat for T2 – T4. Reselect “BPF T1”.

b.Press the F9 key and all filters are automatically adjusted for peak levels.

Automatic Adjustment Method 2 (Adjusts only one filter at a time)

a. Select “BPF T1” and press F8 to automatically adjust it for a peak level.

6.8.2 SQUELCH ADJUST

NOTE: The squelch level can also be set from the front panel as described in Section 3.3.6.

1.Select the channel on the low end of the operating band (Test Ch. 2). channel with LB models and the 150.050 MHz channel with HB models.

2.Connect a SINAD meter with a 4-ohm load to the external speaker jack.

3.Connect an RF signal generator to the antenna jack. Set it to the channel frequency with an output mod- ulated with 1 kHz at the following deviation:

Wideband (30 kHz) Models - 3.5 kHz Narrowband (12.5 kHz) Models - 1.75 kHz

4.Scroll to “SQL” on the computer screen and press the adjust keys to lower the displayed number so that the receiver unsquelches (the 1 kHz tone is heard). Also adjust the volume if necessary.

5.Adjust the signal generator output to obtain 8 dB

SINAD.

6.Press the computer adjust keys to increase the dis- played number to the point where the receiver squelches. Then slowly adjust the number down- ward again until the receiver just unsquelches.

b. Repeat for the other three filters.

Manual Adjustment

a.Connect a SINAD meter with a 4-ohm load to the external speaker jack (see Figure 6-6).

b.Select “BPF T1” and press the adjust keys ( ←/→, PgUp/PgDn, or spacebar/backspace) to obtain minimum distortion.

c.Repeat for the other three filters.

6.8.3 BEEP TONE LEVEL

This adjustment sets the volume of the beep tone that is heard when keys are pressed and at other times (if it is enabled). The computer setup used in the pre- ceding steps is not required for this adjustment. Pro- ceed as follows:

1.Unplug any cable that may be plugged into the microphone jack and locate R60 inside this jack. (see Figure 6-5).

2.Repeatedly press a front panel switch to enable the beep tone and adjust R60 for the desired level.

November 1998

 

Part No. 001-7600-001

6-10

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Contents 761x VHF 764x UHF Conventional Mobile Conventional FM TWO-WAY Radio Table of Contents Table of Contents CONT’D Schematic Diagrams and Component Layouts General Information Accessory 75xx AccessoriesToll-Free 800 Factory ReturnsInternet Home Replacement PartsThis page intentionally left blank General VHF and 7640 UHF Mobile SpecificationsGeneral Information Transceiver Installation Installation and DisassemblyInstalling Microphone Hanger Installing Mounting BracketPower Cable Installation Cable InstallationChanging 20-Ampere Power Cable Fuses Power Cable FusesUsing AN External Speaker Accessory Cable InstallationRemove shield E Transceiver DisassemblyRemoving PC Board Installation Procedure 2-TONE/5-TONE Module InstallationSetting 5-Tone Deviation 2 2-TONE ProgrammingInstallation and Disassembly Operation FeaturesBasic Operation Controls and DisplayTransceiver Back Panel Direct Selection The F1-F4 Receiving and Placing Calls Programmable Functions TIME-OUT TimerOption Key Programmable Functions Function Key Label Description Section NoOutput Power Select Monitor Mode SelectCall Guard Tone Select Channel SelectChannel Scan Priority Channel Sampling Section Programming Programming SetupProgramming Cables Programming SoftwareSpecial Keys and Functions Starting the ProgramMenu Flow File MenuProgram Menu Screen MenuPrint Menu Model MenuParameter Description Bank Select Setup MenuMemory Channel Screen Description LMR Models Ch Atr TimerFrequency Rx/TxLockout Auto ResetScan ToneKey Description Key and Display Assign Screen DescriptionKey Description Label Dtmf Autodial Screen Description RF PowerSelection Bank/FreeParameter Description Continuous Tone Screen DescriptionScan Function Screen Description 2-Tone Code Channel Screen Description Stop TimerResume Auto CHTimer Auto Tx EXO TimerAuto Tx StunCommon Screen Description Expert Screen Description Unique PMR Screens Unique PMR European ScreensCloning Programming ONE Transceiver with Another Memory Channel Screen PMR Models This page intentionally left blank VHF Receiver Circuit VHF 7610 Circuit DescriptionReceiver Mute Circuit Audio Amplifier CircuitVHF Transmitter Circuit Power Amplifier ModuleMicrophone Amplifier Circuit Modulation CircuitPLL Circuit APC CircuitVHF PLL Circuit Pin Port Description VHF IC PIN DescriptionsLine Description Pin VHF I/O Expander IC5 Main UnitVHF Port Expander IC11 Main Unit Pin Port Description NameUHF Receiver Circuit UHF 7640 Circuit DescriptionSecond if System IC1 UHF UHF Transmitter Circuit UHF PLL Circuit PLL Circuit UHFUHF CPU IC1 Port Allocation UHF Power SupplyUHF Port Expander IC13 Main Unit UHF I/O Expander IC12 Main UnitTest Setup Adjustment ProcedureSuggested Test Equipment Equipment Grade and RangeTest Cable Test ChannelsUHF Test Frequencies COMPUTER-AIDED TuningVHF Test Frequencies VHF Adjustments VHF AdjustmentsPreliminary Setup PLL Adjustment VHF ModelsFM Deviation Adjust VHF Adjustments CONT’DOutput Power Adjust Receiver Adjustments VHF Models Dtcs Waveform AdjustBandpass Filter Adjust Squelch AdjustBeep Tone Level Beep Tone Level AdjustmentTransmitter Adjustments UHF Models UHF AdjustmentsPLL Adjustment UHF Models UHF Adjustment Points UHF Adjustments CONT’DUHF Adjustments CONT’D Receiver Adjustments UHF Models Æçìíýõ9+ôý0$,1ý81,7 Parts ListÍäç HUDPLFý&ìçíåý-%ýì+ýìíë.ð7ð$ Íëëðêäíçðíçí Íäæ Ìää HUDPLFý&ìçíåý-%ýì&ýìíé.7ð1 Íëëðêäíçðçìé Ëíí Ëäí HUDPLFý&ìçíåý-%ýìýìíê.ð7ð$ Íëëðêäíçðíçê Ëäì RLOý0/ìçíå$ýì5í.ð7 Íëëðêäíçðçèç 03ì Ýìäëëý9&2ýFDVH 5íéé 5HVý5-ê*-ýìííý9ýõìíýRKPô Íëëðêäíçðìêå 5íéè 5ìèé 5HVý5-ê*-ýìíéý9ýõìííýNýRKPô Æçéíýõ8+ôý0$,1ý81,7 Íêì HUDPLFý&ìçíåý-%ýì+ýìíë.ð7ð$ Íëëðêäíçðíçí Íêë Íäé HUDPLFý+0çí6-ý&+ýíêíýèíí9ý Õéäíðèìëý0+ô Ìèì 5HIý1Rï Êëç Íëëðêäíçðäèë 4éì 7UDQVLVWRUý7&êçê.ý7ìéæ 5íæé 5ìçå 5HVý5-ê*-ýìíéý9ýõìííýNýRKPô 5217ý81,7 Õ9+ý$1ý8+ý02/6ô =HQHUý0$åíèìð0ýõ7ô Æçìíýõ9+ôý&+$66,6ý3$576 Front Unit VHF 7610 Exploded ViewUHF 7640 Exploded View VHF 7610 Block Diagram Schematic Diagrams and Component LayoutsMain Unit Front UnitVHF 7610 Transistor Basing Diagrams Foldout → VHF 7610 Main Board TOP View VHF Main Unit VHF 7610 Main Board SchematicUHF 7640 Block Diagram UHF 7640 Main Board Bottom View J4 T o O p tion al Un it UHF 7640 Main Board TOP ViewUHF 7640 Main Board Schematic VHF/UHF Front Unit Board Bottom View VHF/UHF Front Unit Board TOP ViewVHF/UHF Front Unit Schematic UHF 7640 Transistor Basing Diagrams
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