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Receivers and LO Visualisation

In the Spectral Editor at the top left, the graph displays thefrequency range within which ALMA can observe, the ALMA frequencybands (1-10), the atmospheric transmission curve, and the frequenciesof the first local oscillator and the upper and lower sidebands. Thegraph will also display the position of the basebands and theirbandwidth, once they are defined. The top scale of the graph gives theobserving frequency scale, at the bottom the frequency scale in thesource (rest) frame is displayed. The shift of the two frequencyscales with respect to each other depends on the source velocity whichincludes the convention that was used to calculate the sourcevelocity: optical, radio or relativistic.

The checkboxes labelled Basebands , Other Transitions , BBC Centre Frequencies , Receiver Bands , Side Bands and Transmission control whether or not the indicated information isshown on the graph. The button Select Other Transitions can beused to display additional lines. The Zoom ... buttons can beused to fine-tune the displayed information.

In the graph (see Fig.  10.2 ) the selected receiverband (field Receiver Band ) is represented by the broader hashedband with the blue colour. The narrower band represents the possiblerange of the LO1 frequency. The LO1 frequency, the sidebands and theline to be observed and its identification have colours defined by the Option $\rightarrow$ Colours settings the menu.

The LO1 (and the USB and LSB) and the target frequency can be moved using the left button of the cursor. When changing these frequency settings with the mouse the corresponding fields in the Frequency Setup panel are updated. Moving the LO1 frequency and the sidebands positions allows the user e.g. to observe a particular line together with the main target line.


next up previous contents index
Next: Baseband and Spectral Windows Up: The Visual Spectral Editor Previous: Overview of the Graphical   Contents   Index
The ALMA OT Team, 2011 May 20