Since there is not a variable attenuator between the Gunn and multiplier,
special care must be taken when firing-up the L.O. Before bringing the Gunn
up to its operating voltage ( 
V), apply 
V of bias
voltage to both multipliers. Then as you turn the Gunn voltage above
about 7.5 V, you may see a jump in multiplier current as the Gunn
begins to oscillate. The range of acceptable voltages and currents on
the multiplier change with Gunn power and frequency.
To keep each multiplier's voltage and current within these ranges
you will have to slowly
turn-up the bias voltage on both multipliers as you turn up the Gunn
voltage. Do not exceed the listed bias voltages and currents on either multiplier.
The multiplier and harmonic mixer are biased using the bias boxes provided by Peter Zimmermann. I suggest reading his instructions on operating the LO chain before applying power to the unit.
Calculate the required Gunn, reference, and synthesizer frequencies using the following formulas.
Channel 1:
where, 
LSB; 
USB
Channel 2:
where, LSB; USB
where, LSB; USB+
For example, Let us say you wanted to observe the CI line in the upper sideband of channel 2:
GHz
GHz
GHz
Set the Gunn power and tuner backshorts to the proper values. Look for
a lock signal. The Gunn normally runs with an operating voltage of
V.
Leaving the
X input of the XY plotter connected to the 
of the SIS bias box,
connect the DC output of channel 1 to the Y input of the XY
plotter. You will probably have to reduce the voltage sensitivity of the
Y channel to keep the plotter from going off scale.