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TB9400 Installation and Operation Manual

© Tait Limited March 2015

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 and P25 Phase 2. 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 50

Ω 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 (including single 
base stations) with a 50

Ω load. 

50

Ω termination

(also needed for

single base stations)

maximum of eight base 

station loads on one 

frequency reference output

maximum overall cable 

length is 30m