User's Manual

Operation
RFI-148 & RFI-900 High Output Power Paging Transmitters User Manual Page 29 of 134
The external reference frequency must be configured correctly in order to lock to the external reference (Radio
-> Reference -> Ext. Ref. Frequency). By default, the external reference is configured to 10 MHz but 5 MHz
is also supported.
4.3.5 Absolute Delay Adjustment
The paging transmitter can insert a small artificial delay on data presented on the LIU interface before it is
passed to the digital synthesiser. The delay adjustment can be set from 0 to 40 ms in 5 µs steps. The additional
net delay is accurate to  3 µs.
Absolute delay adjustment can be used for matching delay in:
• Simulcast networks where transmitters from different manufacturers are used.
• Radio and leased line simulcast systems.
4.3.6 RF Diagnostics
The paging transmitter provides an RF diagnostics port output on the back panel. The RF diagnostics port can
be configured for two different modes using the “Isolator Mode” setting:
• Set for Transmitting: The RF diagnostics port will output a signal identical to that of RF out but at a
much lower power level.
• Set for Listening: Insertion loss from RF out to RF diag is decreased to 12 dB. This is a special mode
of operation used for network testing. NOTE: While in listening mode, PTT override is forced to
disable transmit.
LISTEN MODE TIMEOUT
A timeout can be enabled for listening mode. When the listening mode timeout is enabled, the isolator mode
will automatically revert to transmitting mode after the timeout expires. The timeout starts when the isolator
mode is set to listening mode. By default, the listening mode timeout is disabled.
ISOLATOR FEEDBACK
The isolator feedback is a read-only field that indicates the isolator status when the isolator is in listening
mode. When the isolator mode is set to listening, the feedback status will change to “Switching” for one second
and then change to “Listening Mode”. However, if the status changes to “Listening Failure” then there may
be a hardware failure of the mechanical attenuation switch-out.
4.4 Data
Paging data that is to FSK modulate the carrier is externally input from the L-bit and H-bit pins on the LIU
connector. The data encoding implemented by the RFI-148/900 250 is controlled by the Paging Protocol and
the Data Invert. A third parameter, 4-Level Operation, only applies when a 4-level FSK modulation format is
selected. This is described in the following sections.
Radio -> Absolute Delay Adjustment
Radio -> Isolator