Anything to do with the online software, eg. caobs, vis, spd etc.

Moderator: Mark.Wieringa


Postby baerbel » Thu Apr 15, 2010 1:24 pm

SPD commands:

array 12345 # only show antennas 1, 2, 3, 4 and 5

acs # show auto-correlations
noacs # do not show auto-correlations

on fx # show IFx where x is either 1 or 2
off fx # do not show IFx

chan # plot all channels
chan n1 n2 n3 n4 # select channel ranges for IF1 (n1 - n2) and IF 2 (n3 - n4)

(see also www.csiro.atnf.au/observers/docs/3mm/quickstart.html by Kate Brooks & Vince McIntyre)

Pages at www.narrabri.atnf.csiro.au/operations/corr/corr.html are out-of-date
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Joined: Mon Feb 08, 2010 1:27 pm


Postby ste616 » Thu Apr 15, 2010 10:24 pm

Hi Baerbel,

Good start! I'll contribute some more information:

[on/off] acs: turn on/off display of auto-correlation spectra
[on/off] ccs: turn on/off display of cross-correlation spectra
[on/off] fn: turn on/off display of spectra from IF n (where n is a number between 1 and the number of IFs available)

sel [nm]pq: select spectra formed between polarisations p and q on baselines with both antenna n and m (if specified), where both p and q are one of a or b, and n and m represent the available antennae; note that one can specify more than one selection at a time, ie. "sel 12aa 24aa 36bb 56ab"

ch fn chan1 chan2: change the display of IF n to display only channels between chan1 and chan2, eg. "ch f2 513 1537" will display data between channels 513 and 1537 for all IF 2 spectra

sca mode: change the scaling mode of the amplitude axis, where mode is lin (for linear scaling) or log (for log scaling)

x: change between displaying the channel number and the frequency on the x-axis
p: display phases
a: display amplitudes

auto: turn on time averaging of the SPD display
noauto: turn off time averaging

write [file]: writes a Postscript file of the current display to the current directory (the command will also tell you what file it created). If file is not specified, then a generic filename that includes the current time will be used.

Remember that SPD will only ever show 16 or fewer panels in its PGPLOT window, where each panel represents a single baseline and either an auto-correlation or cross-correlation. It will preferentially display the lowest numbered IF first, so panels from IF 1 (if it is enabled) will always be displayed before panels from IF 2, etc. It will then preferentially display the auto-correlations first within each IF, if they are enabled.

Something to be aware of is that when displaying auto-correlations, SPD will show two different-coloured spectra for each polarisation product aa and bb. These different colours show the power when the noise-diode in the receiver is on or off. Also note that selecting a cross-polarisation product will only work when viewing the auto-correlations, even though the correlator is actually computing cross-polarisations for all baselines.
Jamie Stevens
ATCA Senior System Scientist
Site Admin
Posts: 206
Joined: Thu Feb 04, 2010 3:27 pm
Location: Paul Wild Observatory Narrabri NSW


Postby len067 » Fri Apr 23, 2010 2:46 pm

Hi Jamie,

Do you (or anyone else for that matter) know if there is a way to tell which mode the x-axis is currently in i.e. channel or frequency? It can sometimes get really confusing at 20 cm trying to work out whether something is a channel or a frequency (particularly when sleep deprived) and as the "x" command is a toggle you never quite know which state it is currently in (from what I remember there wasn't any obvious label for the x-axis to help with this).


ATCA Expert
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Postby ste616 » Sat Apr 24, 2010 12:38 am

Hi Emil,

As far as I know, there isn't a way of telling which mode SPD is in.

The only band it is really a problem at is at 20cm as you said, and then only when one is zoomed in on a particular frequency range. One thing to remember here is that the 20cm band is frequency inverted, so when the entire band is being viewed in SPD, which will have a central frequency of 1750 MHz, the usable band will appear above the centre in channel mode, and below the centre in frequency mode. I guess that's one way to be sure.
Jamie Stevens
ATCA Senior System Scientist
Site Admin
Posts: 206
Joined: Thu Feb 04, 2010 3:27 pm
Location: Paul Wild Observatory Narrabri NSW

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