• ARINC 429, CSDB and analog tuning capabilities provide a variety of installation options
• Diagnostic read out and wire-saving serial tuning is provided via the Pro Line II CTL-22 control
• Internal diagnostic routines minimize time spent on fault diagnosis
• Three frequency ranges are available (118 to 136; 118 to 137; 118 to 152) to meet current operational requirements
• Optional 8.33/25 kHz channel spacing versions are available to meet current international regulatory requirements
• VHF-422 meets DO-160C HIRF requirements (Category R)
• VHF-422 meets DO-160C lightning requirements (Level 3)
• Versions available for use in installations with GPS receivers
• Meets ICAO Annex 10 FM immunity requirements (DO-186) are met
• Emergency low-voltage operation is provided
• Maintainability is enhanced by comprehensive diagnostic capability and convenient mechanical design
• Significantly increased reliability is provided by a minimized number of parts, highly efficient use of input power and careful thermal design
• Advanced speech processing ensures superior audio quality while receiving or transmitting
• Practical approaches address two perennial communication nuisances: stuck microphones and comm-to-comm interference

Microprocessor technology provides wire-saving serial digital control and built-in diagnostics capability. Collins Pro Line II VHF communications transceivers are designed to meet the worldwide operational needs of business and regional airline and many military aircraft.

The Pro Line II VHF communication transceivers are digital radios that employ microprocessor control of channel selection and diagnostic routines, single-crystal, frequency synthesis and a pulse width modulator for optimal efficiency. The VHF-422 accepts serial digital tuning in Commercial Standard Data Bus (CSDB) or ARINC 429 formats. The VHF-22 accepts serial digital tuning in CSDB or analog formats.

The VHF-422 may be controlled by a serial digital signal from an ARINC 429 control such as the RTU-4200 Radio Tuning Unit. The VHF-22 may be controlled by a serial digital signal from a CSDB control such as the CTL-22. Such installations require significantly fewer wires between the flight deck and the radio rack, resulting in reduced weight and easier installation. Self-diagnostics within the radio are enabled by the self-test function with the results of the internal routine displayed on the panel.

Several performance improvements have been incorporated into these VHF communications transceivers. A reduction has been made in comm-to-comm interference. This was done through the design of a wide dynamic range receiver with sufficient Automatic Gain Control (AGC) to ensure linearity for extremely large desired signals. Only desired signals will affect the AGC; whereas, the first mixer must have enough dynamic range to handle strong interfering signals and small desired signals simultaneously. Intermediate frequencies were selected to minimize any spurious responses.

A reduction has been made in potential for comm-to-nav interference. Improvements in the VHF comm were made through the selection of synthesizer frequencies. The extended-range receiver uses high-side injection below 138 MHz and low-side injection above 138 MHz. The synthesizer will not generate any spurious signals within the nav frequency band into the receiver mixer.

An improved phase-noise squelch has been incorporated into the radio that is immune to impulse noise and receiver gain variations. It is in essence a capture effect squelch operating on the signal-to-noise level in the receiver section of the radio. The receiver also includes an override squelch that assures reception of offset carrier signals. The improved squelch and an extremely effective AGC provide excellent reception regardless of altitude or distance from the station. A broad dynamic range ensures that signals as low as three microvolts will be received as clearly as those of one volt.