Gregorian cal control

DOWNSTAIRS TTL cal selector multiplexor
UPSTAIRS receiver cal multiplexor
CAL diode configurations
Standard gregorian cal block diagram
Online (VxWorks) tcl procedures

07dec17: cal selection fails 13nov17 through 05dec17.. stuck at hcal


All receivers have noise diodes that inject power into the receiver for
calibration purposes. A TTL signal is used to turn the noise diodes
on and off. Some receivers have a high (more power) and a low cal (less power).
The newer receivers also have more than one configuration for the noise diodes
(correlated, uncorrelated, 90 deg phase shift, path reversed).

The TTL signal used to turn diodes on/off is generated downstairs and is
sent to the DOWNSTAIRS TTL cal selector multiplexor. It then goes upstairs
via the fiber optic link. Upstairs the cal signal is sent to the receiver
of interest via the upstairs receiver cal multiplexor.

DOWNSTAIRS TTL cal selector multiplexor:  (top)

    This device is in rack 5 in the receiver room. It has 8 input ports and
one output that is sent to the fiber optic transmitter. The user selects one
of the 8 input ports via the calport routine. The current ports are: This multiplexor can be manipulated with the "if2" or calport commands from vxWorks.


    This transmiter/receiver has a wide bandwidth (about 50mhz) for fast
switching times. There is a single level (on or off) that is sent upstairs
(both polarization's are driven from the same signal).

UPSTAIRS receiver cal multiplexor:  (top)

    The upstairs receiver cal multiplexor takes the 0/1 level from the fiber
optic receiver and sends it to one of the 16 receivers. The port for the
current receiver is automatically setup by the ifsetup routine.

CAL diode configurations:  (top)

    The new receivers have a high and low cal (the difference is generated
via a directional coupler) and 4 different cal diode configurations. If the
diodes are labeled d1,d2 (where d1 goes to Pol A in the straight through case)
then the configurations and keywords are:
keywords code used
in hdr
settings diode config
lcal,hcal 4,5 lo hi uncorrelated cals d1->polA
lxcal,hxcal 2,3 lo hi uncorrelated cals
crossed over
lcorcal,hcorcal 0,1 lo hi correlated cals d1->polA
l90cal,h90cal 6,7 lo hi correlaated cals
with 90 deg phase shift

The configuration is seleted by the ifsetup routine using the setcal routine.

Cal block diagram:

    The  figure shows the standard cal block diagram for the gregorian dome (.pdf)

Online (VxWorks) tcl procedures.  (top)

cal25   on,off        - turn the 25hz cal on or off.
calport 1..8          - select the downstairs ttl cal port.
setcal  configKeyword - select the cal configuration hi,low,corr,uncorr...
corcal  0,1           - turn the correlator ttl cal level on or off.