VS1 Operations and Maintenance Manual Description
Issue 3.1 2013-10-01 Page 1-5
Combiner PWB
See Figure SD-2. The combiner PWB (A10) accepts the RF outputs of the four PA PWBs and
combines them into a single output. This single output is applied to the low pass filter PWB (A11).
The output of the low pass filter PWB (A11) is then applied to the power probe section of the
combiner PWB. Here, three directional couplers monitor the RF signal before it is passed to the
output connctor (J2). Due to each coupler’s proximity and orientation to the RF output signal, RF
voltages are induced in these directional couplers.
The first coupler provides forward and reflected power signals to the combiner/interface PWB (A12)
for signal conditioning purposes.
A second coupler provides an RF Sample output (J4, accessible on the rear panel of the transmitter)
for use by an external exciter, if applicable.
A third coupler provides an RF Monitor output (J3, accessible on the rear panel of the transmitter),
which is a nominal -42 dBc (2 V rms @ 1250 W). This signal is intended for use with a modulation
monitor or spectrum analyzer.
Low pass filter PWB
See Figure SD-2. The low pass filter PWB (A11) accepts the output of the combiner PWB and
attenuates harmonics before applying a filtered RF signal to the output power probe, located on the
combiner PWB.
Combiner interface PWB
See Figure SD-2. The combiner interface PWB (A12) accepts the output of the IPA forward power
coupler and converts it to a dc voltage that is proportional to the RF level through the probe. This
signal is then applied to the exciter/control PWB as the IPA Fwd Pwr sample.
Similarly, the combiner interface PWB accepts the outputs of the transmitter’s output forward and
reflected power couplers and converts them to dc voltages that are proportional to the RF levels
measured by the couplers. These signals are then applied to the exciter/control PWB as the Fwd Pwr
and Refld Pwr samples.
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