Technical Manual

PINEAPPLE TECHNOLOGY, INC.

UTX3KW-A Operating and Service Manual

Page 56

VIII — ADJUSTMENTS AND TUNING

The UTX3KW-A is basically an FCC Type Certied broadband transmitter with a few frequency selective

sub-assemblies. A list of these sub-assemblies are listed below and followed by general instructions where

applicable:

A. MODULATOR — Instructions for making adjustments to the modulator are included in the

Manufacturer’s Instruction Manual.

B. BPU3KW Band Pass Filter comes adjusted to the channel as purchased. To change frequency

would require a tuning adjustment to the lter. To perform this adjustment it is necessary to use a

NETWORK ANALYZER and a signal generator with necessary I/O Adaptors to connect to the lter.

The Technician performing this adjustment should be skilled in tuning Band Pass Filters. If the target

frequency is outside of the tuning range of the lter, it becomes necessary to purchase a new lter.

Replacement lters and service is available from Pineapple Technology, Inc.

C. U600LDV-2 POWER AMPLIFIER MODULE — The U600LDV-2 has three areas where adjust-

ments may be necessary over time or in the event of a frequency change. These areas are:

1. Bias adjustments: The LDMOS FET devices used in these pallet ampliers are set to 500ma/device

side or a total of 1 amp/device. This adjustment can be made on the bench by rst terminating the

input and output with 50 ohm terminations. Apply 31 volts DC to the PA using a power supply that

can provide a minimum of 15 amps. Note: a cooling fan will be necessary to cool the amplier

during this adjustment.

To adjust the bias’ it is best to turn all the bias adjust resistors CCW or to minimum on the pallet

being adjusted. Using a clamp on the AMP Meter connected to the DC Feed terminal — located

on the DC ISOLATION AND CURRENT MONITOR BOARD — measure the current levels. The

rst resistor is increased to 500ma indicated on the Amp meter. Repeat this adjustment for each

additional resistor for reading of 1.0 A, 1.5 A, and 2.0 A. This will indicate that each device half

is set to 500 ma.

This concludes the bias adjustment procedure. This adjustment should be made at any time when a

device has to be replaced. Normal bias ranges from 1.5 amps to 2.3 amps per pallet as indicated on

the ADP500/1000. DO NOT USE THE ADP500/1000 CURRENT READINGS FOR MAKING

BIAS ADJUSTMENTS.

2. PA PALLET RF circuit tuning: These circuits are broadband and xed tuned providing no adjust-

ments. Any tuning at this level is performed by the factory.