EFJohnson 761X Dtcs Waveform Adjust, Receiver Adjustments VHF Models, Bandpass Filter Adjust

Page 61

ADJUSTMENT PROCEDURE

VHF ADJUSTMENTS (CONT’D)

2.Select the low power channel in the middle of the band (Test Ch. 5 - 160.050 MHz). On the computer screen, scroll to “MOD N” if setting narrow band deviation or “MOD W” if setting wideband deviation.

3.Monitor the transmit deviation with a communica- tions monitor set as follows: HPF = Off, LPF = 20 kHz, De-Emphasis = Off, Detector = (P–P)/2.

4.Key the transmitter using the test cable switch and

set the following maximum deviation by pressing the adjust keys (←/→, PgUp/PgDn, or spacebar/

backspace). Unkey the transmitter.

Wideband (30 kHz) Models - 4.2 kHz Narrow Band (12.5 kHz) Models - 2.1 kHz

5.If the transceiver operates on both narrow and wide band channels, select Test Ch. 7 and also adjust the deviation on that channel (see note in Table 6-1).

6.4.4 DTCS WAVEFORM ADJUST

1.Select a channel in the middle of the band pro- grammed for DTCS (Test Ch. 8 - 160.050 MHz). On the computer screen, scroll to “DTCS N” if setting a narrow band channel or “DTCS W” if setting a wideband channel.

2.Key the transmitter and view the demodulated sig- nal on the CRT of a communications monitor.

3.Press the adjust keys on the computer so that the waveform appears as follows:

Set For

Flat

Waveform

4.If the transceiver operates on both narrow and wide band channels, select Test Ch. 8 and also set the waveform on that channel (see note in Table 6-1).

6.5 RECEIVER ADJUSTMENTS (VHF MODELS)

6.5.1 BANDPASS FILTER ADJUST

1.Select the channel on the low end of the band (Test Ch. 2 - 146.050 MHz).

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 (30 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.

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 6-4).

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.

6.5.2 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 - 146.050 MHz).

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

November 1998

 

Part No. 001-7600-001

6-6

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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 InstallationRemoving PC Board Transceiver DisassemblyRemove shield E Installation Procedure 2-TONE/5-TONE Module InstallationSetting 5-Tone Deviation 2 2-TONE ProgrammingInstallation and Disassembly Operation FeaturesTransceiver Back Panel Controls and DisplayBasic Operation 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 MenuMemory Channel Screen Description LMR Models Setup MenuParameter Description Bank Select Ch Atr TimerFrequency Rx/TxLockout Auto ResetScan ToneKey Description Key and Display Assign Screen DescriptionKey Description Label Dtmf Autodial Screen Description RF PowerSelection Bank/FreeScan Function Screen Description Continuous Tone Screen DescriptionParameter 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 CircuitVHF PLL Circuit APC CircuitPLL Circuit Line Description VHF IC PIN DescriptionsPin Port 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 ChannelsVHF Test Frequencies COMPUTER-AIDED TuningUHF Test Frequencies VHF Adjustments VHF AdjustmentsPreliminary Setup PLL Adjustment VHF ModelsOutput Power Adjust VHF Adjustments CONT’DFM Deviation Adjust Receiver Adjustments VHF Models Dtcs Waveform AdjustBandpass Filter Adjust Squelch AdjustBeep Tone Level Beep Tone Level AdjustmentPLL Adjustment UHF Models UHF AdjustmentsTransmitter Adjustments 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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