MNT-PTX-150
Doc Ref :
150-100
Issue
:
1.00
Page :
5
SONIK - 1999
The final frequency output from the second mixer is filtered, buffered and amplified to
300 mW at 50 ohms, suitable for presentation to the Power amplifier modules.
Note that the TCXO of 9.6 MHz supplies the DSP, first LO and second LO to provide the
accuracy required for final frequency. The DSP circuitry actually uses 38.4 MHz which is
derived from a crystal at that frequency phase locked to the 9.6 MHz TCXO.
Note also that for high stability options, the 9.6 MHz TCXO is replaced when an external
reference signal is applied to the BNC connector at the rear of the Transmitter. Selection
of this function is via software.
Automatic level control (ALC) of the exciter is affected by the on board Microprocessor
in the Exciter module.
The Exciter output is coupled via coaxial cable to the 20W driver amplifier in a separate
compartment in the chassis.
The driver comprises 2 RF amplifier stages, a Harmonic filter and directional coupler for
generation of forward and reverse power voltage analogs.
The output of the 20W driver amplifier goes into a power splitter, and the two 90 degree
out of phase output signals from the power splitter are feed into two 75W power
amplifiers.
The outputs of the two 75W power amplifiers are then combined to produce 100W
continuous RF output power.
The forward and reverse power output is also monitored using a directional coupler. The
exciter microprocessor computes VSWR from the directional coupler outputs.
ALC is also effected in the PA to ensure stable output for all environmental and external
conditions.
The transmitter is designed to operate from a 24VDC power source with the
internal AC power supply generating the required voltage.
A 37 Pin DIN female socket provides the connection for Data, Clock, mode, channel
change, and PTT control from an external Line interface unit
. (Refer to ‘Installation
Instructions’ for details regarding pin connections)
.
If no external PTT control exists, provision is made for PTT control by the detection of
incoming data on the TX DATA (Lbit) pin of the 37 way connector.
(Hang time for this
automatic PTT control is selectable in software).
A DB9 female socket provides access for either a PSTN dial modem or a PC.
The transmitter can be monitored by a central or local computer for automatic diagnostics
or polling.
The PC and RDK software can be used on site to reprogram parameters of the transmitter.