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Configuring an IRIG Output

VersaSync can accommodate up to four IRIG RS485 outputs, or up to to one IRIG DCLS/10V and up to five IRIG DCLS/TTL outputs. Supported IRIG output formats are A, B, E, G (DCLS and AM) and NASA 36. Additionally, frequency/resolution values of no carrier/index count interval, 1kHz/1ms, 10 kHz/0.1 ms, and 100 kHz/10 ms, as well as IRIG input coded expressions of the fields BCDTOY, CF, SBS, and BCDYEAR are supported.

To configure an IRIG Output:

  1. Navigate to INTERFACES > OUTPUTS : IRIG Output [x]. The Status window will open, displaying the the currently configured settings:
  2. Click the Edit button in the lower left corner to open the Edit window:

The following configurable settings are available:

  • Signature Control: Used to control when the IRIG modulation will be present. This function allows the modulation to stop under certain conditions; see also Signature Control.
  • Format: Used to configure the desired IRIG output formatting. The available choices are:
    • IRIG A
    • IRIG B
    • IRIG E
    • IRIG G
    • NASA 36
  • Modulation: Changes the type of output signal modulation. The available choices are:
    • IRIG DCLS Only: TTL-modulated output
    • IRIG AM Only: Amplitude-modulated output. The amplitude of the output is determined by the value entered in the Amplitude field.
  • Frequency: The IRIG modulation frequency. This is determined by the configuration of Format and Modulation Type. See IRIG Carrier Frequencies for details.
  • Coded Expression: Defines the data structure of the IRIG signal, where:
    • BCD = Binary Coded Decimal
    • TOY = Time of Year
    • CF = Control Field
    • SBS = Straight Binary Seconds
  • Note: The available options will vary according to the values of Format and Modulation Type.

  • Control Function Field: IRIG signals have an optional section in the data stream that can be used to include additional information (such as the present year, for example). This field allows the Control Field section of the IRIG output to be defined. The available configurations are:
    • Fields conform to RCC 200-04: IRIG spec 200-04 specified a location for year value, if included in this field.
    • Fields conform to IEEC 37.118-2005 (IEEE 1344): Control Field contains year, leap second and daylight savings time information.
    • Fields conform to Spectracom IEEE C37.118-2005: Has been extended to support one-month leap second notification.
    • Fields conform to Spectracom Format: Year is included in Control Field but not in the same location as RCC-2004 output (year is offset by one position).
    • Fields conform to Spectracom FAA Format: A unique IRIG output Control Field that contains satellite lock status and time error flags.
  • Note: The available options will vary according to the configurations of Format and Modulation Type.

  • Amplitude: The peak-to-peak output voltage level into a 600 Ω load is adjusted by entering a digital control value in this field. The level adjustment has no effect on TTL outputs, only on AM formats. The value of 128 will cause the Mark amplitude to be about 5Vp-p into high impedance. A value of 200 results in an output amplitude of about 9Vp-p into high impedance.
  • Note: These are nominal values only. Actual values will vary from unit to unit. To adjust the level precisely, connect an oscilloscope to the output connector when adjusting.

  • Offset: Provides the ability to account for IRIG cable delays or other latencies in the IRIG input. The Offset value is entered and displayed in nanoseconds (ns). The available Offset range is -500 to +500 ms.

For IRIG frequency and output specifications, see IRIG Standards and Specifications.

For information on IRIG output resolution, see About the IRIG Output Resolution.