Operating instructions

RF Technology PA501 Page 6

2 CIRCUIT DESCRIPTION

1.4 Amplifier I/O Connections

The PA501 has three connectors on the rear panel.

1.4.1 RF Input

The RF drive is delivered via a BNC connector. The absolute maximum power that

should be applied to this connector is 17 Watts.

1.4.2 RF Output

The RF output signal is available from an N-type connector.

Pins Function

1, 2, 3, 4, 5, 14, 15, 16, 17 Positive supply

9, 10, 11, 12, 13, 22, 23, 24, 25 Ground (negative supply)

8 ALC output

Table 1: Pin connections for the 25 pin “D” connector on the rear panel

Note: The amplifier is capable of delivering as much as 120 Watts continuously.

In certain conditions

an RF power of 180 Watts or more can be available via this

connector. This power level can cause burns like any 180w power source.

Appropriate care should be taken when working on the PA501 to avoid making or

breaking connections when the amplifier is operating, and to avoid RF burns

through close proximity to live connections, etc.

1.4.3 25 Pin Connector

The 25-pin “D” connector provides connection to ground and dc power, and from the

automatic level control (ALC) circuit. The pin connections are given in table 1.

2 Circuit Description

The following descriptions should be read as an aid to understanding the block and

schematic diagrams shown in figures 1 and 2.

2.1 Block Overview

The PA501 is comprised of two stages of RF amplification, a directional coupler

sensing forward and reverse power flow, an output low-pass filter and sundry associated

control and monitoring circuitry. The second RF amplifier employs two transistors

operating in parallel, a power splitter following the first RF

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Excessive powers may be available, for example, in the event of a failure of the ALC loop,

such as may arise if the ALC feedback connection is broken.