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WRS Low Jitter Daughterboard

Faq

Last edited by Mattia Rizzi
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FAQ

Q: What are the typical figures for ADEV and Jitter that I may expect with a WR Switch with the low jitter board?

Modified ADEV at 1s < 5E-13 (typical 4E-13)
Modified ADEV at 10s < 5E-14
Jitter (10 Hz to 100 kHz) < 2 ps RMS (typical 1.5 ps RMS)

Q: In a network with a standard (off-the-shell) WR Switch (WRS) in Grandmaster mode, using a boundary WRS with the low jitter board would result in a improved timing and jitter performance?

A: No, because the phase noise of the standard Grandmaster is very high. You will get an improvement if you use as Grandmaster WR Switch that has the low jitter daughter-board installed

Q: Can I benefit of the performance of the WRS Low jitter board if the GM is using it but the boundary switch is a standard one?

A: Yes, you will experience a 10 dB reduction of noise.
Better improvements can be achieved if

  • you cover the boundary VCTCXO (VM53S3) of RTV3140 silicone resin (hardware modification) OR

  • you increase the bandwidth of the boundary VM53S3 (software modification) with Kp=10000 and Ki=300

Q: What to do if I want to have the very best jitter performance?

A: Switch off the Ethernet management interface. The jitter will be slightly improved by 10 to 20%. The stability will not change.
See the measurement results.
Likely the small improvement you may get will not be worth it as you will not be able to manage your switch remotely over Ethernet anymore.

24 March 2017