DescriptionSPD displays data from the correlator/spectrometer, either in the lag domain - the correlation function, as measured directly by a correlator, or in the frequency domain - the spectrum, which results from the Fourier transform of the correlation function in the case of a correlator, or from direct measurement in the case of a spectrometer. The user can select which of the products contained within the correlator/spectrometer configuration to display and in what form to display them.
SPD can also display time bin profiles and time bin images for correlator/spectrometer configurations which provide time or pulsar binning. In the case of pulsar binning, the de-dispersed pulsar bin profile can be displayed.
For the correlation function, the default action is to display only that part of the function which is actually measured in the correlator. For autocorrelations, this will generally be only be the positive lags. If negative lags are requested for autocorrelations with the 'lags' command, the positive lag measurements are mirrored into the negative lags for display.
CommandsType the following commands - minimum match - in response to the prompt SPD>
SPD has a standard command line editing and prior command recall facility.
SPD> modeDefines the mode in which the select command operates in selecting products to display.
SPD> mode v - selection by variable or product number. SPD> mode b - selection by baseline and/or polarisation. SPD> mode - show current mode setting.
SPD> selectSelects which products to display.
1. Selection by product number ( mode v ):
In the following examples, the letters refer to the type of display. viz.
- l - The lag spectrum, i.e. correlation function.
- a - The amplitude of the frequency spectrum.
- r - The real part of the frequency spectrum.
- i - The imaginary part of the frequency spectrum.
- p - The phase of the frequency spectrum.
- d - The amplitude difference of the frequency spectrum, using a previously stored reference.
- q - The amplitude quotient of the frequency spectrum, using a previously stored reference.
The numbers refer to the product numbers in the order they appear in the correlator/spectrometer configuration.
If only numbers are used, then the display type is set to the global display type (see below).
SPD> select 2 5 7 - displays spectra of products 2, 5 & 7 on seperate plot panels. SPD> select 4>12 - displays spectra of products 4 to 12 on seperate plot panels. SPD> select l1 a1 - displays lag and frequency spectra of product 1 on separate plot panels. SPD> select a1&2 - displays frequency spectrum of products 1 & 2 on one plot panel. SPD> select a1&2 a3&4 - displays frequency spectra in two panels, each containing two products. SPD> select a2-1 - displays the difference frequency spectrum between two products. SPD> select 1-2 4+5 - displays difference and sum frequency spectra in two panels.
Special Parkes Multibeam Selection:
SPD> select mbN - displays lag or frequency spectra of N beams, two polarisations per plot panel, in the special Parkes multibeam layout.
2. Selection by frequency band/baseline/polarisation ( mode b ):
A new plot panel is created for each baseline and frequency band selected.
Baseline, polarisation, frequency selection:
SPD> select 1aa - displays all baselines with antenna 1, polarisation AA, frequency 1. SPD> select 12ba - displays baseline 1*2, polarisation BA, frequency 1. SPD> select 14cc - displays baseline 1*4, polarisation AA, frequency 2. SPD> select cd - displays all baselines, polarisation AB, frequency 2. SPD> select 24 - displays baseline 2*4, all polarisations. SPD> select * - displays all active products
Frequency only selection, displaying all previously selected baselines/polarisations for the selected frequencies:
SPD> select f2 - display frequency 2 only. SPD> select f1 f3 - display frequencies 1 and 3 only. SPD> select f1-4 - display frequencies 1 to 4 only. SPD> select f* - display all frequencies. SPD> select z1 - display CABB zoom band 1 only. SPD> select z1 z3 - display CABB zoom bands 1 and 3 only. SPD> select z1-2 - display CABB zoom bands 1 to 2 only. SPD> select z* - display all CABB zoom bands.
Note: The polarisation types must be enabled with the ON/OFF command (see below). Initially only AA, BB, CC and DD are enabled. The use of C and D to denote the A & B polarisations of the second frequency is allowed only for certain two frequency operating modes. It is not allowed in cases where more than two frequencies may be available, for example with MOPS and CABB. In these cases control of which frequencies are displayed is via the fn parameter of the SELECT or ON/OFF commands.
Then use one of the global display type commands (see below) to select the display type.
SPD> select bp11 - displays the time bin profiles for baseline 1*1, all polarisations. SPD> select pp11 - equivalent to above. SPD> select dp - displays the de-dispersed pulsar bin profiles for all baselines and polarisations.
The bin profile plots the integral over frequency of the amplitude spectrum against bin number. The limits of the integral, by default the entire spectrum, can be defined by the bchannels command. bchannels also defines the frequency range over which the de-dispersion is carried out.
SPD> select bi - displays the time bin image for all polarisations. SPD> select biaa - displays the time bin image for polarisation AA.
The bin image shows colour coded amplitude on the Z-axis as a function of bin number on the X-axis and frequency channel on the Y-axis. If the biq command is set ( see below ), the Z-axis shows a quotient obtained by subtracting and normalising by the band shape, computed from an average of the spectra of all bins included in the plot. X-axis limits are set by the bpbins command. Y-axis limits are set by the bchannels command.
SPD> biq - displays quotient in the bin image plots. SPD> nobiq - displays amplitude in the bin image plots.
SPD> l or SPD> a or SPD> p or SPD> d or SPD> r or SPD> iSets the global display type and changes all current panels to this display type.
SPD> xFor frequency domain plots, toggles the X axis units between frequency and channel number.
SPD> arrayIn baseline mode, defines the currently active antennas.
SPD> array 1346 - antenna 1,3,4,6 active, antennas 2,5 inactive. SPD> array - show the currently active antennas.
SPD> binsIn baseline mode, and when time or pulsar binning is active, defines the currently selected time bins.
SPD> bins 1-5 10-16 - selects bins 1 to 5 for frequency one, 10 to 16 for frequency 2. SPD> bins 1.3.5 10.11 - selects bins 1,3 & 5 for frequency one, 10 & 11 for frequency 2. SPD> bins - show the currently selected bins.
SPD> on OR SPD> offIn baseline mode, defines which frequencies and polarisations are displayed, and whether auto-correlations and/or cross-correlations are displayed.
SPD> on ab ba cd dc - turn on display of all cross polarisation products. SPD> off cc cd dc dd - turn off all second frequency polarisation products. SPD> on f1 f4 - turn on display of frequencies 1 and 4. SPD> on ccs - turn on cross-correlations. SPD> off acs - turn off auto-correlations. SPD> on - display which types are currently displayed.
Note: The 'on' or 'off' commands for frequencies are probably more conveniently carried out with the 'select fN' command (see above).
SPD> scaleAllows the plots to be scaled on the Y axis. The default is auto-scaling.
SPD> scale l -0.01 0.01 - scale lag plots to cover the range -0.01 to 0.01 SPD> scale bp 0 200 - scale bin profile plots to cover the range 0 to 200 SPD> scale bi -1 1 - scale bin image plots to cover the range -1 to 1 SPD> scale a - return to auto-scaling for amplitude plots. SPD> scale - autoscale all plots. SPD> scale log - autoscale amplitude plots on a logarithmic scale. SPD> scale log 30 - set the range of log plots to 30dB.
SPD> freqFor frequency domain plots, allows a selection of a range of frequencies to plot. The default is the full frequency range of the spectrum.
SPD> freq [f1] 1146 2125 - display the frequency range 1146 MHz to 2125 MHz for band 1. SPD> freq f2 1146 2126 - ditto for frequency band 2. SPD> freq - reset to full band for all frequency bands. SPD> freq f3 - reset to full band for frequency band 3. SPD> freq z2 1410 1420 - set frequency range to plot for CABB zoom band 2.
SPD> channelsAllows a selection of a range of frequency channels to plot. The default is all channels.
SPD> channels [f1] 100 200 - display channel range 100 to 200 for frequency band 1. SPD> channels f2 200 500 - display channel range 200 to 500 for frequency band 2. SPD> channels 100 200 300 500 - display channel range 100 to 200 for frequency band 1 AND channel range 300 to 500 for frequency band 2. SPD> channels - reset channel selections to defaults.
SPD> bchannelsAllows the selection of a range of frequency channels to be used to compute the bin or pulsar profile. The default is the range of channels defined by the 'channels' command. The format is the same as the 'channels' command.
SPD> lagsAllows a selection of a range of lag channels to plot. The default is all channels.
SPD> lags [f1] -800 100 - display lag channel range -800 to 100 for frequency band 1. SPD> lags f2 -100 500 - display lag channel range -100 to 500 for frequency band 2. SPD> lags -200 200 -100 100 - display lag channel range -200 to 200 for frequency band 1 AND lag channel range -100 to 100 for frequency band 2 SPD> lags - reset lag channel selections to default.
SPD> bpbins OR SPD> ppbinsIn baseline mode, and when time or pulsar binning is active, defines the range of bins over which bin profiles and bin images are plotted.
SPD> bpbins 20 30 - displays the bin profile for bins 20 to 30. SPD> ppbins - reset to the full range of available bins.
SPD> avgWhen the next data arrives, resets the averaging buffers and starts a vector averaging in time of the frequency spectra. This also results in a time averaging of bin profile and bin image displays.
SPD> noavgWhen the next data arrives, reverts to non-averaging mode.
SPD> saveSaves the current frequency spectra amplitudes in a stored reference area.
SPD> rsaveRepetetively saves the previous frequency spectra amplitudes in a stored reference area. This provides a means to continuously monitor changes, using for example the difference display. Mainly useful for debugging problems, or looking at how RFI is changing with time.
SPD> autoWhen the next data arrives, resets the averaging buffers and enables an automatic averaging mode where the averaging is reset at the start of each scan.
If the selected display is frequency spectrum amplitude and a scan is on a reference position then the averaged data will be saved in the reference area and subsequent signal scans will be displayed as quotient spectra.
SPD> noautoDisable automatic averaging mode.
SPD> layoutControls the layout of plot panels. The default layout is the smallest square (NxN) layout which will contain the number of plot panels, with the exception that a two panel layout defaults to 1x2, representing :
(number of panels in X) x (number of panels in Y). The maximum number of panels is currently set to 16.
SPD> layout 3x4 - 3 panels in X by 4 panels in Y. SPD> layout [0x0] - revert to default layout.
SPD> write [[no]c[olour]] [filename]Writes a colour (the default) or nocolour=greyscale postscript file of the current display to the filename, if given, otherwise to a constructed filename which includes date and time. The path used is the environment variable SPD_HARDCOPY, if defined, otherwise the directory from which SPD was started. A message is printed identifying the actual filename used.
SPD> ssSet SPD into "single shot" mode. The automatic update of the display is disabled. Entering a further ss command causes the display to be updated. This command is particularly useful when using SPD over slow links, to reduce data flow.
SPD> nossCancel "single shot" mode and resume continuous updates of the display.
SPD> quitExits the program.
Last updated: 18 May 2012, Warwick Wilson