Tait TN9275, Инструкция по установке и эксплуатации

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84 Installation
TB9400/TN9275 Installation and Operation
© Tait International Limited May 2023
4.6.6 Connecting an External Frequency Reference
Notice
An external reference is required for simulcast operation.
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 reciter
automatically detects the frequency of the external reference and
configures itself accordingly. The stability of this reference should be as
shown below. For more details, see Technical Note TN-2674 Providing
Synchronization to Tait Networks.
If an external reference is required, enable the “external reference absent”
alarm (Configure > Alarms > Control).
Use a 50

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 BNC goal post adaptors (see
Figure 4.12 ). The maximum overall cable length is 30m. Terminate the last
connection (including single base stations) with a 50

load.
Multicast P25 Phase 1
P25 Phase 1
P25 Phase 2
B and H bands
K4 band
All bands
Not required
100 parts per billion
100 parts per billion
Simulcast P25 Phase 1
P25 Phase 2
All bands 10 parts per billion
Figure 4.11 Daisy-chaining an external frequency reference input
50

termination
(also needed for
single base stations)
maximum of eight base
station loads on one
frequency reference output
maximum overall cable
length is 30m