Initially, tune the receiver for maximum total power in the
traditional manner.
Check the magnetic field. Turn on the magnetic field, and either look at
the
or
to adjust the field strength to minimise/suppress the general Josephson
structure and give the
Some critera
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.
850 GHz Receiver Tuning in Detail
There are Two Multipliers for this Receiver:
720-840 GHz, RPG Physics, x12 , Self biased (1998 model, 4 tuners, refer to data sheet for settings)
600-660 GHz, RPG Physics, x6 Self biased (2000 model, 4 tuners, refer to data sheet for settings)
Monitor the
and recheck from time to time that the
is still in lock.
Optimum junction current is typically about 9-11uA.
From now on the tuning process is iterative. That is,
optimize the SIS current by adusting all the available micrometers, as well as the
When finished tuning, make a final check of the
Any Josephson oscillations will seriously effect the receiver stability.
Make sure the
is set somewhere between 2.1-2.15 mV.
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
the
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