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User Guide
48
temperature range changes in a range of ±10 ºC, then the error becomes closer to
3000 ns.
There are some interesting facts related with errors induced by temperature variations.
We could try to describe two typical situations to illustrate these facts:
1. A test is to be done in a room where access to GNSS is not possible and there is
no other signal that could be used as an alternative reference input. xGenius is
synchronized in a different room at a different temperature and then moved to the
test location. If the temperature difference in both rooms is larger than four
degrees Celsius then the 1000 ns holdover performance could not be guaranteed.
Not only phase and time measurements will be affected; the frequency in the test
location will also be different to the room where the equipment was synchronized.
2. The test unit is synchronized in a laboratory and then transported to the test loca-
tion. The temperature in the laboratory is similar to the test location but during
transport the temperature is different. Now, frequencies in the laboratory and the
testing site will be closer one each other because temperatures are the same in
both locations. However, the phase and time error accumulates during transport.
The longer the transport time and the temperature difference, the larger the error.
The conclusion is that it is better to minimize the transport time when time and
phase is to be tested because the accumulated error will be difficult to remove
from the test result.
2.7.Using the Clock Reference Output
The xGenius clock reference output enables you to synchronize any external
equipment with a clock signal generated by the tester or to connect the internal /
recovered clock to an oscilloscope, spectrum analyser or other equipment. The
reference clock output is therefore very useful for many tests related with network
synchronization. These are the clock reference output ports and formats allowed by the
test unit:
• Clock/PCM (Port Ref. In/Out): The clock reference output is encoded as a fre-
quency or PCM signal. Options included in this set are 2048 kHz, E1,1544 kHz, T1,
5 MHz and 10 MHz. This signal is transmitted through the REF IN/OUT RJ-45 port.
For this reason, this option is available only if a clock reference input has not been
previously configured over the same port.
• ToD (Port Ref. In/Out): Clock reference output constituted by a 1 PPS / ToD inter-
face transmitted through the RJ-48 REF IN/OUT port. There are two ToD protocols
supported: NMEA, ITU-T G.8271. These are automatically detected. This option is
available only if a clock reference input has not been previously configured over the
same port.
• 1 PPS (Port Ref. In/Out): Generates a 1 PPS output synchronized (phase and fre-
quency) with the local oscillator through the RJ-48 REF IN/OUT port. For this rea-
son, this option is available only if a clock reference input has not been previously
configured over the same port.
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