Indoor Broadband Transmitter – ITX21-100
IM4030013-1 Rev – 1
1.0 INTRODUCTION
The ITX21-100 shown in Figure 1 is a solid-state broadband transmitter that converts a
VHF input signal of 119 MHz to a microwave signal of 2.159 GHz.
The ITX21-100transmitter consists of the following assemblies (refer to Figure 2).
1. Upconverter – for converting the incoming VHF signal to microwave. The
upconverter section contains all components necessary for upconversion, i.e. local
oscillator, mixer, as well as band-pass and notch filters.
2. Power Amplifier – The amplification is accomplished with minimum distortion by a
state of the art linearised Gallium Arsenide FET microwave power amplifier. The
power amplifier is protected from failure due to overheating by an internal
temperature sensor. The sensor circuit automatically switches off the amplifier D.C.
power when the amplifier temperature exceeds 158 degrees F (70 degrees C).
3. Power supply system – The microwave modules are powered from a +12 VDC
switching power supply. The local oscillator is powered from a +12 VDC linear
power supply. A 24 VDC power supply powers the downconverter. A +5 VDC
voltage regulator is used to for the power amplifier’s TTL circuit.
4. Monitoring and Diagnostic Circuits – Depending on the configuration of the
compact transmitter, the input and output can be continuously monitored without
interruption of service with a standard TV set or a field strength meter by means of a
front panel dual function coaxial connector. Diagnostic DC voltages can also be
continuously monitored via a front panel meter with a selectable switch or a rear
panel multi-pin connector.
5. On-Delay Timer Assembly – Upon start-up of the compact transmitter, a binary
counter is used to delay voltage to the power amplifier. This gives the +12 VDC
switching power supply time to stabilize.
The ITX21-100transmitter can be equipped to operate on either 120 or 240 VAC at 50 to
60 Hz. This option is specified by customer request, and each unit is shipped according to
this specification.
Complete specifications are listed in Section 6.0.
