Introduction

The hardware and software has been designed to guide the user through the correct SIS receiver tuning procedure which, in theory at least, provides for stable receiver operation. There are a number of major changes in the receivers. All 5 mixers now have magnets. There are 3 new control computers. These are operated by portable touch panels, using small menus of options. Also, a Y factor device has been added. This is a cold load (currently a small dewar of liquid nitrogen that needs to be refilled every day) with a rotating blade in front of it. This blade has alternating holes and hot load sectors. A mirror above the 345/650 GHz receiver moves into the beam on a linear stage, directing the beam from the dewar into the entrance window of the new Y factor device.

Important Note: We have observed on some rare occasions that the Computer I/O hangs. This is probably due to static discharges on the computer ground. Fortunately this does NOT effect receiver operation so do not worry about it while observing. Unlike the old computer, which reset the junctions when it reset, the new one has no affect on them. You only need to reset it if you need to tune. If you push a "button" on the menu and nothing happens please follow the following simply directions:

1. Do not touch the manual bias knob as this will alter the receiver setting.
2. Reset the computer with the red button on the front panel. (This can take up to 1 minute).
3. Follow main menu procedure below. The receiver will return to it original bias position.