Crescend Technologies P35XXE Users Manual

User Manual

1. GENERAL DESCRIPTION

1.1. INTRODUCTION

This manual contains installation and operating information for the Crescend High Power VHF
Power Amplifier. The manual is organized into three sections as follows:

Section 1. General Description

Section 2. Installation

Section 3. Operating Information

1.2. PRODUCT DESCRIPTION

The Crescend Technologies High Power VHF RF power amplifier is designed for paging and
other VHF applications that use a single carrier constant envelope waveform. The amplifier is
designed to be powered from a 48 VDC source, but optionally incorporates an internal AC power
supply. The amplifier covers a 150-174 MHz without retuning. Amplifier specifications are shown
in Table 1-1. There are four input ranges available as shown in Table 1-2. Closed loop power
control is used to maintain a constant output power under varying voltage, signal input level,
frequency and output load conditions. Several design features work to protect the amplifier under
adverse conditions.

The amplifier is designed to fit into 5.25 inches (3RU) of vertical 19 inch rack space. The front
panel includes LED indicators for monitoring status and alarm conditions. This information is also
accessible via a monitor connector on the rear of the amplifier. The fan assembly draws ambient
air in from the front and blows the air across the heat sink fins out the back of the amplifier.

• Notice: The manufacturer’s rated output power of this equipment (see Table 1-1) is specified
for single carrier operation using constant-envelope modulation. This equipment is NOT
designed for multiple-carrier operation, nor is it intended to be used with non-constant envelope
modulation types.

Table 1-1. Amplifier Specifications

Specification Value

Instantaneous Bandwidth 150-174MHz

Output Power 350W

Input Impedance

Output Impedance

Table 1-2. Amplifier Input Power Ranges

Input Power Designator Code Input Power Range

5 5-10 W

10 10-20 W

20 20-50 W

50 50-100 W

50Ω

50Ω

Nominal Gain (350W Output)

18.5dB

15.5dB

12.4dB

8.5dB

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2. INSTALLATION

2.1 INSTALLATION INSTRUCTIONS

The amplifier is designed for installation in a rack that permits access to the rear of the rack for
connection of DC power, RF, and monitor/control cables. The amplifier must have a minimum of
3 inches of open space in front and to the rear of the chassis to allow adequate air flow and
ventilation.

To install the amplifier proceed as follows:

1. Mount the amplifier in equipment rack and secure in place.

2. Connect a properly sized 50 ohm cable and load (antenna) to the RF OUT connector on
rear of amplifier.

3. Connect the transceiver/exciter output to RF IN connector on rear of amplifier.

4. If monitoring of PA is desired, connect alarm cable to MONITOR connector on rear of
amplifier module. See section 3 for more details about monitor pins.

5. Connect ground wire to ground stud on rear of amplifier if desired.

6. If unit is the 48 VDC version, measure primary DC input voltage of power supply. DC
input voltage should be +48 +/- 0.5VDC. Turn off DC voltage.
NOTE:

• Make sure power supply DC is well filtered and well behaved with minimal
voltage overshoot.

• Keep DC wires as short as possible to minimize inductance induced voltage
transients.

• Size DC Wires properly to handle the load current to minimize voltage drop.

WARNING: Turn off external primary DC power before connecting DC power cables.

7. Connect positive primary power wire (+48VDC) to terminal marked +48VDC and negative
primary power wire to GND terminal next to it on rear of amplifier.

8. Check your work before applying DC voltage to the system. Make certain all connections
are tight and the DC wires are going to the correct terminals.

9. If the unit has the optional power supply: Connect unpowered AC cord to AC plug on
rear of amplifier.

10. Refer to Section 2.2 for initial start-up procedures.

2.2 INITIAL STARTUP

To perform the initial start-up, proceed as follows:

1. Check to ensure that all input and output cables are properly connected and tightened.

Note: Use high quality coaxial cable and connectors. Properly install all connectors for reliability.

CAUTION: Before applying power, make sure that the input and output of the amplifier are

properly terminated in 50 ohms. Do not operate the amplifier without a load
attached. Refer to Table 1-1 for input power requirements. Excessive input power

will damage the amplifier.

NOTE: The output coaxial cable between the amplifier and antenna must be 50 ohm cable

and adequately sized to handle the rated power level with additional stresses from
high VSWR taken into account.

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2. Apply 48 VDC from your power supply or AC mains power (depending on whether amplifier
has optional power supply) to the amplifier with the supplied line cord. The fans will power on.
Check that all four fans are running.

3. Visually check the indicators on the front of the amplifier and verify the following:

a. The PWR ON indicator (green) is on.
b. All other LED indicators (red and yellow) are off.

4. Set the external exciter power level so that it is within the specified input power range and apply
the RF signal to the amplifier input port. The amplifier will deliver nominally 350W at the output
connector. The green exciter drive status LED will illuminate when the RF drive is detected.
This LED is meant to give the user a general indication that the exciter is active and is
delivering output power when troubleshooting an alarm condition. However, it does not indicate
that the minimum input power level has necessarily been reached.

5. Remove the RF input signal. The output power will drop to zero. Only the Power On indicator
will be illuminated. Amplifier is ready for use.

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