STOAT

STOAT is the name of the program that is used to control the receiver selection on the 26m telescope. It is currently a DOS-based program, running in an emulator on the desktop of the rx26m machine. This is accessible via VNC (vncviewer rx26m). STOAT's main screen is shown below & the program is controlled by keyboard commands indicated by the square brackets.

Selecting a receiver

Always make sure that the telescope is either parked or in the service position before changing receivers. Otherwise, there's a serious risk of damage if cabling gets caught on the platform as it moves. Once it's safe to do so, select option 3 from the main menu and then select the appropriate receiver from the list. The receiver selection page will list some supply voltages & cryo temperatures - see below.

Check that the display in rack 3 shows the selected receiver number after a second or so. If you've changed from one receiver to another, the focus platform should start moving to the new focus position. If it does not, try toggling the switch above the Rx display from "Auto" to "Manual" and back again. Head back to the main page by pressing the Escape key, and then a (to go to the utility menu, a.k.a Main page)

Using the expansion port (Quadrature Hybrid & crossover switch)

From the main page, select option 6.

For most experiments (except at L-band) you should have the Quadrature Hybrid OUT (indicated with the SW1=1 = Quad out line) and the crossoverswitch in "direct" mode (SW2=a = Direct). If the hybrid is in when it shouldn't be, the recorded polarisations will not be circulars but rather some strange elliptical blend. If the display for SW2 shows it as crossed, then the recorded polarisations will be reversed from the nominal (so RCP will be in channel 2 rather than channel 1).

Go back to the main page after you've checked the settings.

Checking cryogenic status

From the main page, select option 7.

If everything is working, the multifeed 70K/20K readings should be ~60/30 and the L-band 70K/20K readings should be ~80/35. If any of the readings are more than ~10 degrees above these nominal values, it may indicate an impending problem. Getting in early saves a lot of time overall, so please let Brett and Eric know about this as soon as possible.