RF Technology PA220
Page 9
4
SPECIFICATIONS
3.2 Tuning Procedure
3.2 Tuning Procedure
Adjustment of the matching circuits is carried out with the aim of
•
ensuring that the specified power is available
•
balancing the load reasonably equally between the power transistors, and
•
obtaining acceptable efficiency in the power transistors.
Note that the factory alignment procedure is complicated, but allows a given unit to
operate across a full 10% bandwidth, without further adjustment. Alignment without
appropriate equipment can leave the amplifier unstable or otherwise unable to meet
specification. However, the procedure below will usually provide adequate
performance.
1.
Disconnect the ALC line.
2.
Set the RF source to deliver 15W at the highest frequency in the band over which
the PA is specified.
3.
Measuring the RF output power, adjust C10, C24, C102, C112, C58, C59, C104 and
C114 to obtain maximum output.
4.
Measuring the collector currents of Q1 and Q2 at the test socket, adjust C58 and C59
to reduce and balance the currents, but keeping the power above the required level.
5.
Proceed to carry out the power setting procedure in section 3.1.
4
Specifications
4.1 Description
The PA220 power amplifiers are designed for use with the T220 series transmitters to
provide 100 Watts of RF output. Output power is regulated by connecting the ALC
output to the ALC input of the driving exciter. The drive from the transmitter module is
then automatically adjusted to maintain the required output.
The regulated power level can be preset over a wide guaranteed range from 25 to 100
Watts or more, depending on the available input power and the model.
Sensing circuits are provided to protect the output transistors from excessive
temperature. If the heat sink temperature rises to 80C, the input drive will be reduced to
prevent damage.
