Cables & References
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      What Cable Delay Compensation Value Should be Used for VeEX's Multi-band (Quad Constellation) GNSS/GPS Antenna?

      The typical cable delay for the Quad Constellation Multi-band antenna's 5m (15 ft) coaxial cable is 25 ns.

      The typical cable delay compensation value to be used for the portable Quad Constellation Multi-band antenna is 25 ns (VeEX P/N: Z99-99-033G).

      • Coaxial Type: RG-174
      • Cable Length: 5 m
      • Velocity of Propagation: 66% or 5.05 ns/m 
      • Theoretical Delay: 25.25 ns

      The actual cable delay value of the antenna can be measured following a quick procedure using a TDR with direct time-of-flight reading, like the CX41 (no conversions, estimates or approximations required). Note that other portable GNSS antennas come with different coax cable lengths (e.g., 3m, 4m, 5m) as well as any added cable extensions.

      GNSS Antenna Cable Delay measured with a CX41 TDR

      Tip: For Precision Timing applications, test and measurement in particular, it is recommended to measure and label all test cables and antenna cables with their intrinsic physical delays.

      This multi-band GNSS portable active antenna supports the 1.2 GHz and 1.6 GHz bands, with a high LNA gain of 38 dB, supporting GPS L1C/A and L2C, GLONASS L1OF and L2OF, Galileo E1B/C and E5B, BeiDou B1 and B2I.

      A multi-band GNSS Receiver card (optional P/N: Z99-99-034P) is required, to take advantage of the multi-band antenna, when used for High Precision timing applications. Supports tracking of up to eight concurrent satellite signals, including the GPS (L1C/A, L2C), Galileo (E1B/C, E5B), GLONASS (L1OF, L2OF), and BeiDou (B1I, B2I) bands.

      What If You Don't Have a Proper TDR?

      The next best thing one could do to get the best estimate is: Measure the cable length, read the coaxial cable's markings, find its datasheet online and use its typical Velocity of Propagation to calculate the approximate delay. For example, a 3m cable with VP = 5 ns/m (1.4837 ns/ft or 66% of the speed of light) could be approximated to 15 ns. However, longer cables may introduce more error and some cables may not be properly marked.

      Glossary

      GNSS - Global Navigation Satellite Systems (generic for USA GPS, Russia's GLONASS, Europe's Galileo and China's BeiDou)

      LNA - Low Noise Amplifier

      TDR - Time Domain Reflectometer

      VP - Velocity of Propagation (in ns/m or ns/ft)

      VP% - Velocity of Propagation as a percentage of the speed of light.

      Related Test Solutions

      • RXT-1200 - Advanced Modular Test Platform
      • TX340s - Advanced Multi-Service Test Set
      • MTTplus - Modular Test Platform
      • CX41 - Coaxial Time Domain Reflectometer (TDR)