User's Manual

AT71-250 Transmitter Owner’s Manual

MOD 4791: 2:1 UHF Combiner

The UHF 2:1 combiner is a module operates over the all UHF band from 470 to 806 MHz, without

adjustments.

Moreover, it has an internal low pass filter mainly designed to reduce the 3rd harmonic components

generated by the amplification chain. It also has a power level detector circuit, reading the values of

direct (FWD) and reverse power (REF).

A directional coupler built in on the same hardware structure It also has a directional coupler circuit

responsible for providing a sample of the signal after the amplification before the output mask filter.

The RF signal out from this sample is intended to be used as a RF sample for the non-linear pre-

correction system.

MOD 4812: DC/DC 2kW Power Supply

The 4812 module is a DC / DC converter with +370 Vdc input and +50Vdc output. Its function is to

lower the voltage delivered by the AC / DC converter with PFC (Phase Correction Factor) and

perform insulation.

The circuit topology chosen for this circuitry is the topology named full-bridge, with synchronism

performed on the secondary, set up with 4 powers MOSFET’s on the primary of the transformer.

The control circuit is assemble on a separate printed circuit board named; CIP 8696. This printed

circuit board has a TPO that is used to precisely adjust the nominal voltage of the power supply.

The complete module 4812 is composed by the following boards:

- Power PCB (DC/DC): CIM 3918 and CIP 8708.

- Control PCB: (DC/DC): CIM 3855 and CIP8696.

MOD 4812 - Technical Specifications:

Parameter

Specification

Input Voltage

370Vdc

Switching Frequency

27KHz

Nominal Output Voltage

50Vdc

Nominal Power

3kW

Max Current

60A

MOD 4810: 2kW PFC Power Supply