A7 Pulse Generator; All Phase Lock; A3 Source; Source Super Low Band Operation - HP 8753E Service Manual

A step recovery diode in the pulse generator produces a comb of harmonic
multiples of the VCO output. These harmonics provide the high band LO (local
oscillator) input to the samplers. In low band and super low band the operation
the pulse generator is turned off.

All Phase Lock

This assembly compares the f&t IF (derived from the source output in the
integrated into the drive for the A3 source assembly.
This assembly includes a 3.0 to 6.8 GHz YIG oscillator and a 3.8 GHz cavity
oscillator. The outputs of these oscillators are mixed to produce the RF output
signal. In Option 006 (30 kHz to 6 GHz) the frequencies 3.0 to 6.0 GHz are no
longer a mixed product, but are the direct output of the YIG Oscillator. The
signal tracks the stable output of the synthesizer. The ALC (automatic leveling
control) circuitry is also in the A3 assembly.

Source Super Low Band Operation

The Super Low Band Frequency Range is 10 kHz to 300 kHz. These frequencies
are generated by the Al2 Reference Board. They are the amplified output of
the fractional-N synthesizer. This output is not phase locked and is not subject
to ALC control. Refer to 'lhble 12-1.
I
Theory of Operation 12-15