LO must be on the receiver to set the magnetic field.
Minimized the magnetic field (current) since it suppresses the superconducting
energy gap, which results in degraded receiver performance.
On the 230 and 345 GHz receivers, use the
(Total Power vs SIS bias) and/or the
to check you are not getting the
Finally, check the
to make sure the receiver is responding to the correct harmonic.
(This is usually only a problem with the 345 GHz receiver).
230 GHz Receiver Tuning in Detail
Note: The 210-270 GHz and 180-220 GHz Mulipliers have NO micrometers and
are self biased!!
LO Procedure: Do Nothing, except for locking the Gunn
Rx Tuning Procedure: Refer to the
Receiver Tuning Cookbook.
Bias the junction to
Set the Magnetic field Current to about 20-35 mA (+ or -).
and recheck from time to time that the
is still in lock.
Optimum juncton current is typically about 9-11uA.
From now on the tuning process is iterative. That is,
optimize the SIS current by adusting the:
When finished tuning, make a final check of the
Any Josephson oscillations will seriously effect the receiver stability.
Make sure the
is set to 2.35-2.45 mV.
Refer to Tuning Hints.
to make sure that there is no second photon step!!
Finally it is best to put the SIS bias voltage on a flat spot
of the P/V curve (dP/dV=0). This is critical because in this way
Please do remember to
the total power on the Sky when all is set and done and you are ready to observe! This guarantees
that the AOS are presented with a fixed IF power level.
Last but not least, do perform standard Y-factor measurements to make sure that the receiver properly works