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New Dual Polarization 4.5 - 5.0 cm Receiver for 26m Telescope 2001/02/22

The new dual polarization receiver for the 4.5 - 5.0 centimetre wavelength band became operational on 2001 Feb 22. This replaces the previous single-polarization receiver. The two polarization modes received are left- and right-hand circular.

This receiver is used primarily for spectroscopy of the excited hydroxyl transitions at 6.0 GHz and of methanol at 6.7 GHz. These transitions produce maser emission in regions where massive stars are forming. Observations can be made either using the telescope as a single "stand-alone" instrument, or as part of a global VLBI network of radio telescopes to resolve the maser positions at the level of a thousandth of a second of arc.

The photograph below shows the receiver with a ruler marked in centimetres for scale. The microwave feed connects to the square aperture on the top of the package. In use all this is inside a vacuum jacket, and it is cooled down to -257 Celsius, or 16 degrees above absolute zero, to minimise receiver noise. Click on the photo for a larger view.

This photograph shows Microwave Engineer Mike Ainley, on the right, and Microwave Technician Johan Kriel, on the left, who constructed the receiver. The receiver itself is on the aluminium frame between them. The refrigerator that cools the package using helium gas is under the receiver section shown in the upper photograph. Click on the photo for a larger view.