User's Manual

TB9400 Installation and Operation Manual Installation 91
© Tait Limited December 2013 (Draft)
5.6.6 Connecting an External Frequency Reference
For K4 Band, the internal frequency reference accuracy is inadequate, and
an external reference must be used. An external reference is also required
for simulcast. The external reference frequency can be 10MHz or
12.8MHz, with an input level of 300mV
pp
to 5V
pp
. The stability of this
reference should be better than 50 parts per billion (for non-simulcast) or
≤1 part per billion (for simulcast). The reciter automatically detects the
frequency of the external reference and configures itself accordingly.
If an external reference is required, enable the external reference “Absent”
alarm (Configure > Alarms > Control).
Use a 50Ω coaxial cable (RG58 or RG223) to connect the external
reference to the base station’s external reference frequency input. You can
daisy-chain up to eight base stations using F-junctions. The maximum
overall cable length is 30m. Terminate the last connection with a 50Ω load.
Figure 5.12 Daisy-chaining an external frequency reference input
50Ω termination
maximum of eight base
station loads on one
frequency reference output
maximum overall cable
length is 30m