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section IV theory of operation 4.1 INTRODUCTION This publication provides all the specifications and information necessary to test, troubleshoot, and repair the VHF-422( ) VHF Comm Transceiver. Refer to the Pro Line II Comm/Nav/Pulse System Installation Manual (CPN 523-0772719) for installation, operation, and on-aircraft fault isolation information. Refer to Table 4-1 for a list of equipment covered in this manual and Table 4-2 for the VHF-422( ) specifications. An overall view of the VHF-422( ) is shown in Figure 4-1. 4.1.1 License Requirements An aircraft radio station license is required to operate the VHF-422( ) VHF Comm Transceivers. A Federal Communications Commission (FCC) Application for Aircraft Radio Station License, Form 404, must be submitted to obtain the station license. Application for Aircraft Radio Station License, Form 404, is available by writing to the FCC, P.O. Box 1030, Gettysburg, PA 17326. Figure 4-1. VHF-422A VHF Comm Transceiver Revised 10 September 2001 4-1
4.2 PURPOSE OF EQUIPME N T The VHF-422( ) transceivers are remote-mounted, multichannel VHF voice transceivers providing AM voice communications in the frequency range from 118.000 through 136.975 or 151.975 MHz. The VHF-422A/B transceivers provide channel spacing in 25-kHz increments. The VHF-422C/D transceivers provide channel spacing in either 8.33- or 25-kHz increments. The A, B, C, or D suffix on the equipment type number indicates the frequency range of each transceiver as shown in Table 4-1. The last three digits of the VHF- 422A/B part number defines the bandwidth of the receiver circuits. The 0X1 and 1X1 part numbers have a narrow bandwidth and are intended for operation in areas using 25-kHz channel spacing with or without offset carriers. The 0X2 and 1X2 part numbers have a wider bandwidth and will operate satisfactorily in areas where the received carrier frequency varies as much as 13 khz from nominal. All VHF-422C/D transceivers have narrow bandwidth receiver circuits. A frequency save feature in VHF-422A/B units with 1XX part numbers retains the last frequency used by the transceiver and automatically retunes the transceiver when primary power is reapplied. The 0XX part numbers have connector keying specifically for the Beech Starship. Units with -X2X part numbers are compatible with RTCA/DO-160D, section 21, category H emissions in the GPS band (1.575 GHz). Table 4-1. Equipment Covered. EQUIPMENT *COLLINS PART NUMBER FREQUENCY RANGE SELECTIVITY **NORMAL ***EXTENDED NARROW WIDE #FREQUENCY SAVE VHF-422A 622-7292-001 X X VHF-422A 622-7292-002 X X VHF-422A 622-7292-101 X X X VHF-422A 622-7292-121 X X X VHF-422A 622-7292-102 X X X VHF-422A 622-7292-122 X X X VHF-422A 622-7292-123 X X X VHF-422B 622-7293-001 X X VHF-422B 622-7293-002 X X VHF-422B 622-7293-101 X X X VHF-422B 622-7293-121 X X X VHF-422B 622-7293-102 X X X VHF-422B 622-7293-122 X X X VHF-422B 622-7293-123 X X X VHF-422C 822-1115-001 X X VHF-422C 822-1115-021 X X VHF-422D 822-1116-001 X X VHF-422D 822-1116-021 X X * Part numbers ending in 0XX are keyed specifically for the Beech Starship. Part numbers ending in 1XX are keyed for other aircraft. ** Normal frequency range is 118.000 to 136.975 MHz. Normal frequency range on VHF-422C is 118.000 to 136.992 MHz. ***Extended frequency range is 118.000 to 151.975 MHz. GPS system compatible. Features reduced low-frequency transmitter-input audio response. # Frequency Save is removed on units with Service Bulletin 8 installed. Revised 10 September 2001 4-2
Table 4-2. Equipment Specifications. CHARACTERISTIC Certification TSO FAA -C37c, -C38c EUROCAE ED-23, ED-24 FCC Parts 15 and 87 (modulation designators 6A3, 13A9) Environmental RTCA document DO-160A, categories /A2E1/B/JY/EXXXXXZ/BZ/AZA (Refer to Table 4-3 for additional information.) EUROCAE ED-14A Physical Size 3/8 ATR, short, dwarf Height 85.3 mm (3.36 in) max Width 96.5 mm (3.80 in) max Length 353.8 mm (13.93 in) max Weight 2.13 kg (4.7 lb) nominal Mounting Remote mounted in UMT-12 (preferred) or 390R-19 (alternate) mount Mating connector Collins 1/2-height Thinline II, 52 pin (CPN 634-4192-002; includes connector shell (CPN 634-1022-001), 34 contacts (CPN 372-2514-110), and coax insert (CPN 372-2519-040)) Maintenance requirements On condition. Electrical Transmitter specifications Output power 16-W min into a 52-Ω resistive load. Modulation 85% modulation capability with less than 15% distortion; 95% limiting Duty cycle 1-minute transmit, 4 minutes receive Emergency low-voltage operation 6-W min with 18-V dc input power Frequency range VHF-422A 118.000 to 136.975 MHz VHF-422C 118.000 to 136.992 MHz VHF-422B/D 118.000 to 151.975 MHz Channels VHF-422A 760, 25-kHz increments VHF-422B 1360, 25-kHz increments VHF-422C 8.33-kHz increments from 118.000 through 136.992 MHz VHF-422D 8.33-kHz increments from 118.000 through 136.992 MHz; 25-kHz increments from 137.000 through 151.975 MHz Frequency stability VHF-422A/B ±0.0015% VHF-422C/D ±0.0005% Frequency control Commercial Standard Digital Bus (CSDB) or ARINC 429 serial digital bus (see inputs section for additional information) Revised 10 September 2001 4-3
Table 4-2. Equipment Specifications. CHARACTERISTIC Receiver specifications Sensitivity 3 µv for 6-dB (s+n)/n Selectivity VHF-422A/B -XX1 units Typical 6 db at ±8 khz, 60 db at ±20 khz -XX2 units Typical 6 db at ±15 khz, 60 db at ±40 khz VHF-422C/D For channels between 118.000 and 136.992 MHz, selected as 1XX.000, 1XX.025, 1XX.050, and 1XX.075 and all channels between 137.000 MHz and 151.975 MHz for D units: 6 db: ±8 khz minimum 60 db: ±20 khz maximum For all other channels: 6 db: ±2.78 khz minimum 60 db: ±7.37 khz maximum Spurious Response VHF-422A/B 10-mV spurious signal produces no more output than a desired signal producing 6 db (s+n)/n VHF-422C/D Attenuated at least 80 db relative to the desired response at or beyond the second adjacent channel. Responses at either adjacent channel are attenuated at least 60 db relative to the desired response. Squelch Automatic (phase noise reduction) with carrier override AGC characteristics 6-dB maximum variation from 5 µv to 1 V Emergency low-voltage operation Meets all specifications at 18-V dc input power Power/Straps Input power (P101-49, 50) Receive 16.5 W (0.6 A at 27.5 V dc) Transmit 137.5 W (5.0 A at 27.5 V dc) Power gnd (P101-41, 42) Signal gnd (P101-2, 31) Power on relay + (P101-37) 1.3 W (46 ma at 27.5 V dc). +28 V dc applied to this pin energizes an internal relay which applies power (P101-49, 50) to the unit. Power on relay (P101-38) Ground for power on relay + (P101-37) signal. Burst/Continuous tune select (P101-7) Ground = burst tune; open = continuous tune. Controls type of ARINC 429 data used. With continuous tuning, an ARINC frequency control word is continuously received every 200 ms. With burst tuning, at least 30 frequency control words are received every 1.5 s. Port A/B select (P101-14) Ground = port A; open = port B. Controls ARINC 429 ports. ARINC 429/CSDB select Ground = CSDB; open = ARINC 429 (P101-32) Receiver compressor disable Ground = receiver compressor disabled; open = receiver compressor enabled (P101-9) Squelch disable (P101-36) Ground = squelch disabled; open = squelch normal Revised 10 September 2001 4-4
ROCKWELL COLLINS INSTRUCTION BOOK (REPAIR MANUAL) VHF-422( ), PART NO 622-7292-001 VHF-422( ) VHF Comm Transceiver INSTRUCTION BOOK (REPAIR MANUAL) (523-0773785, 5TH EDITION, DATED SEP 10/01) TEMPORARY REVISION NO. 23-12-40-02 Subject: Revised Table 4-2. Insert facing page 4-4, 23-12-40. In the specification for Input power the Transmit power is revised to read: VHF-422A/B 137.5 W (5.0 A at 27.5 V dc). VHF-422C/D 168 W (6.0 A at 27.5 V dc). 23-12-40 Temporary Revision 2 Page 1 of 1 523-0773785-02511A Aug 30/02
Table 4-2. Equipment Specifications. CHARACTERISTIC Unit ID A (P101-28) Defines the unit as Comm 1, Comm 2, or Comm 3 as follows: Unit ID B (P101-27) Comm 1 Comm 2 Comm 3 Unit ID A (P101-28) Open Ground Open Unit ID B (P101-27) Open Open Ground Inputs Self-Test enable (P101-19) Ground (for at least 500 ms) = self-test enabled; open = normal operation Keyline (P101-35) Ground = transmit; open = receive Mic audio H (P101-13) L (P101-1) 150 Ω unbalanced with excitation current for a 50- to 600-Ω transistorized dynamic microphone. Carbon microphones can be used but are not recommended due to their poor audio quality. Frequency control CSDB data in A (P101-40) B (P101-39) CSDB signals are differential signals with each line varying from +5 V dc to ground (the B signal is the inverse of the A signal). Data transfer rate is 12,549 b/s. Refer to maintenance section for a detailed description of data words. ARINC 429 input Port A-A (P101-47) Port A-B (P101-48) ARINC 429 signals are differential signals with each line varying from +5 V dc to 5 V dc (the B signal is the inverse of the A signal). Data transfer rate is 12,500 b/s. Refer to maintenance section for a detailed description of data words. Port B-A (P101-45) Port B-B (P101-46) Port C-A (P101-3) Port C-B (P101-4) Outputs Fault monitor out (P101-20) 27.5 V dc (18 V min, 200 ma max) = normal operation; open = diagnostic faults present Note During normal operation, in the ARINC 429 mode, the transceiver routinely monitors critical circuits for proper operation. When no faults have been detected, the fault monitor out is at 27.5 V dc. If a fault is detected, fault monitor out goes to an open condition. During self-test, if any diagnostic conditions are encountered, then fault monitor out will go to an open state for the duration of the test. Audio outputs Note The transceiver contains a single audio amplifier. Both sidetone and received audio are available at the combined audio output. An internal relay separates these signals into received audio and sidetone outputs for installations that require separate outputs. Receiver audio out H (P101-18) 100 mw into a 600-Ω load with a 3-µV RF input. Receiver audio provides the received audio signal. L (P101-17) Sidetone audio out H (P101-26) 100 mw into a 600-Ω load with a 3-µV RF input. Sidetone audio provides the transmitted audio signal. L (P101-25) Combined audio out H (P101-30) 100 mw into a 600-Ω load with a 3-µV RF input. Combined audio provides both transmitted and received audio signals. L (P101-29) SELCAL audio out H (P101-34) 0.5 V rms across into a 600-Ω load with a 3-µV RF input. SELCAL audio provides noncompressed received audio signals. L (P101-33) Revised 10 September 2001 4-5
Table 4-2. Equipment Specifications. CHARACTERISTIC Data outputs CSDB data out A (P101-44) B (P101-43) Capable of driving up to five loads. CSDB signals are differential signals with each line varying from +5 V dc to ground (the B signal is the inverse of the A signal). Data transfer rate is 12,549 b/s. Refer to maintenance section for a detailed description of data words. ARINC 429 output Port A-A (P101-51) Port A-B (P101-52) Port B-A (P101-11) Each port capable of driving up to five loads. ARINC 429 signals are differential signals with each line varying from +5 V dc to 5 V dc (the B signal is the inverse of the A signal). Data transfer rate is 12,500 b/s. Refer to maintenance section for a detailed description of data words. Port B-B (P101-12) Noise squelch test (P101-6) Used for monitoring noise squelch state. Ground = audio output disabled (squelched). (Noise level at the noise squelch detector is above the preset threshold.) +12 V dc = audio output enabled. (Noise level at the noise squelch detector is below the preset threshold.) Carrier squelch test (P101-5) Used for monitoring carrier squelch state. Ground = audio output disabled (squelched). (AGC voltage is below the preset threshold of the carrier squelch circuit.) +12 V dc = audio output enabled. (AGC voltage is above the preset threshold of the carrier squelch circuit.) AGC test (P101-10) Provides AGC voltage testpoint to rear connector. Simulcomm (P101-21) Ground from opposite side comm keyline reduces the receiver gain to reduce interference when transmitting. Table 4-3. Environmental Qualifications. CONDITION Temperature and altitude Categories A2 and E1. Temperature Operating 55 to +70 C ( 67 to +158 F) Storage 55 to +85 C ( 67 to +185 F) Altitude Categories A2 and E1. Category A2. Certified for installation in a partially controlled temperature and pressurized location where pressures are no lower than an altitude equivalent of 4600m (15 000ft) msl. Category E1. Certified for installation in a nonpressurized and noncontrolled temperature location in an aircraft that is operated at altitudes up to 21 300m (70 000ft)msl. Humidity Category B. Certified for a severe humidity environment - Level I. Vibration Category J. Certified for fuselage mounting in a fixed wing turbojet or turbofan aircraft. Category Y. Certified for fuselage mounting in a piston or turbojet rotary wing aircraft. Explosion proofness Category E. Certified for installation in a location where an explosive atmosphere may occur as a result of leakage or spillage. Waterproofness Category X. Certified for installation in locations not subject to falling water (including condensation), rainwater, or sprayed water. Fluids susceptibility Category X. Certified for installation in locations not exposed to fluid contamination from fuel, hydraulic fluids, oil, solvents, etc. Sand and dust Category X. Certified for installation in locations not subject to blowing sand and dust. Fungus resistance Category X. Fungus resistance test not performed. Salt spray Category X. Salt spray test not performed. Revised 10 September 2001 4-6
Table 4-3. Environmental Qualifications. CONDITION Magnetic effect Category Z. Unit causes a 1 deflection of an uncompensated compass at a distance less than 0.3m (1.0ft). Power input Category B. Certified for use on aircraft electrical systems where primary power is from engine driven alternator/rectifiers or dc generator where a significant capacity battery is floating on the dc bus at all times. Category Z. Certified for use on aircraft electrical systems not applicable to any other category. For example, a dc system from a variable range generator where a small capacity or no battery is floating on the dc bus. Voltage spike Category A. Certified for installation in systems where a high degree of voltage spike protection is required. Audio frequency susceptibility Category Z. Certified for use on aircraft electrical systems not applicable to any other category. For example, a dc system from a variable range generator where a small capacity or no battery is floating on the dc bus. Electromagnetic compatibility Category A. Certified for operation in systems where interference-free operation is desired. 4.3 OVERVIEW 4.3.1 Introduction This paragraph is intended as a brief introduction to the general principles involved in the VHF-422( ). It is intended for those who have little or no previous contact with this type of airborne equipment. The treatment here is by no means exhaustive and the reader is invited to consult other sources for additional information. The VHF-422( ) is used with a radio control unit, an antenna, and the aircraft audio system to provide 2-way VHF voice communications. The transceiver accepts either ARINC 429 or Commercial Standard Digital Bus (CSDB) tuning data from a radio control unit. The transceiver provides simultaneous ARINC 429 and CSDB output data. The VHF-422( ) uses digital technology to read either ARINC or CSDB serial input data and generate both ARINC and CSDB serial output data. A digital frequency synthesizer under microprocessor control is used to tune the receiver and transmitter circuits. 4.3.2 Installation Configurati o ns Refer to Figure 4-2 for an overall view of a typical VHF-422( ) installation. 4.4 VHF-422A/B FUNCTION AL THEORY OF OPERATION (REFER TO FIGURE 4-3) 4.4.1 Interface Circuits All input and output signals to the comm transceivers are applied through the rear connector and interface circuits on circuit cards A1 and A6. The interface circuits provide noise filtering, transient protection, digital output data buffering, fault monitor output buffering, and ARINC input port selection under control of the ARINC 429 processor. 4.4.2 ARINC 429 Processor The ARINC 429 processor circuits on circuit card A7 convert all ARINC 429 input data to CSDB data so that it can be used by the main control microprocessor when the transceiver is operating in the ARINC data in- Revised 10 September 2001 4-7
put mode. The ARINC 429 processor also continuously converts all CSDB output data from the main microprocessor to ARINC 429 format so that both ARINC and CSDB output data is available regardless of the operating mode of the transceiver. A fault monitor output signal is provided by the ARINC 429 processor whenever the diagnostic bit in the CSDB output data is set by the main microprocessor and the transceiver is operating in the ARINC data mode. Figure 4-2. VHF-422( ) Installation Overview Revised 10 September 2001 4-8