5700MSC-IP
IP Network Grand Master Clock & Video Master Clock System
Revision 0.2 Page - 25
3.2.2. Selecting the Frequency Reference Type
The frequency reference for the 5700MSC-IP is selected with the Freq Reference Src menu item in the
Frequency Ref menu off the INPUT root menu. When GNSS is selected, the 5700MSC-IP will use the
GNSS receiver attached to the GPS port on the rear of the unit (see section 3.2.13). When set to Ten
MHz, the 5700MSC-IP will look for a 5MHz or 10MHz continuous wave (CW) signal on the frame
reference 1 BNC, frame reference 2 BNC or reference loop input HD-BNCs (see section 3.2.12).
When set to Video, the 5700MSC-IP will lock to an analog video sync signal (auto-detected) that is
applied to frame reference 1, frame reference 2 or the reference loop HD-BNC connectors (see
section 3.2.5). When set to Internal, the 5700MSC-IP will free-run off its internal reference (see section
3.2.12.1).
The Inputs status screen in the STATUS root menu can be used to view which frequency references
have been detected by the 5700MSC-IP. The first three lines indicate status of video sync, 5MHz or
10MHz detection, and GNSS status.
3.2.3. Selecting the Genlock Range
The Genlock Range menu item in the Frequency Ref menu selects which oscillator is used when
locking to a video sync or CW reference. When Narrow is selected, the high-stability oven controlled
quartz oscillator (OCXO) is used and the VCXO runs as backup. When Wide is selected, the voltage
controlled quartz oscillator (VCXO) is used and the OCXO runs as backup. It should be noted that
when the frequency reference source is set to GNSS or Internal Ref, the genlock range is forced to
Narrow mode (OCXO) regardless of this menu setting.
In the event that the frequency reference is lost, the 5700MSC-IP will free-run using the selected
oscillator. The Narrow range OCXO has extremely high stability which will translate to very low drift.
This also translates into lower jitter on the outputs. Another advantage of the Narrow range is that it
allows use of the Slow re-lock mode that prevents glitches when re-locking to a reference (see section
3.2.4). The disadvantages of the Narrow range are that it requires a very tight reference source (±0.1
PPM) and requires a longer time to fully lock. The OCXO also requires five minutes of warm-up time
before reaching full stability once the unit has been powered on.
The Wide range VCXO provides very fast lock times with a wide lock range (±15 PPM) which means it
can lock to just about any reference signal. It can be useful if the 5700MSC-IP reference source
changes frequently such as in a post-production facility. The Wide range cannot be used when locking
to GNSS or when free-running on the internal reference. In almost all cases, the Narrow range is
superior and should be left as the default selection.
In the event that the frequency reference is lost when locked in Wide mode, the
5700MSC-IP will freerun on its VCXO. Note that this oscillator can freerun at a
frequency outside the Narrow mode lock range which may cause problems for
downstream 5700MSC-IP units. The Wide oscillator is also capable of going beyond
the frequency tolerance specifications stated in ITU-R BT.601 and SMPTE ST 292-1.
Operating outside the range of ±10ppm may cause locking issues for downstream
equipment.
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