Explanations for SkyPipePlotter Applet

Joachim Köppen DF3GJ Kiel/Strasbourg/Illkirch May 2004

Contents

• How we start
• Plot
• Read URL
• File Info
• Channels
• Operations
• Calibrate
• Cal.Table
• Period

• the Applet with example data
• ISU RadioJove Home page
• my Applet Index
• my Home Page

When the applet comes up, we no choice but to Click to start

Then the default file is loaded and displayed:

On the left hand side is a calibration sequence, on the right a periodic signal. Though it looks interesting, it unfortunately is local night-time interference which we are still busy hunting down!

To the top of the screen you'll find the name of the current file, and just below there are a number of buttons for navigating between the various pages. These are described below.

The Plot page

drag & zoom

click on this Button, then drag a rectangle from upper left to lower right over the plot area which you want to zoom in. Releasing the mouse button will display the zoomed view.

unZoom

will switch back to the full view.

Y: lin.Voltage

This Choice selects between the various ways to present the data:

• linear voltage: the normal way to show SkyPipe data, i.e. in linear amplitude of the audio voltage coming out of the sound card
• log(voltage): the logarithm of these values. This is useful when we want to show strong signals but also details of weak ones.
• dB(kT0): only after calibration, the signals can be shown in noise temperature taken in decibels above room temperature (293 K).
• kK: this displays the signal as noise temperature in thousands of Kelvin

Manual Ranges

In the beginning, the TextFields display the dates and times of the start and the end of the plotted observations, and the minimum and maximum voltage value. We may change these values, and by clicking put ranges the plot is done with the new values.

finish at

can be clicked to give finish after which then refers to the time span of the displayed data

put ranges

forces a redisplay with the current plotting ranges. These new plotting ranges then are used as the full view

ranges from zoom

reveals the ranges in x and y shown by the currently used zoomed view

full time span

reveals the entire time span of the data read from the file. If you click put ranges the plot will show the entire data.

x = and y =

when you click with the mouse at any point of the plot, the time and the y-value will be displayed (not shown here)

The following screen gives a zoomed view of the calibration steps. The logarithmic display shows the lower steps much better. Also we see that the full time span is 14 min 34 sec, while the zoomed view shows only about 6 min.

Read URL

To load another file, simply enter in the long TextField at the top the filename, which can be the complete URL of a file - e.g. on your own Web site - and click Read URL.

Note that when loading a new file any calibration done or entered via the calibration table is kept in the program and the new data can be shown based on that earlier calibration.

File info

All the details of the observations, stored in the file, are displayed on this page. Note that I took another data set which had a more interesting content than my example file...

Channels

For each of the channels (maximum: 8) found in the SkyPipe file, we can

• choose the colour of the curve. Default is red. Click on refresh to show the data in the chosen colour.
• select whether a channel is plotted (plot) or not. Default is yes.
• select whether a channel can be modified (mod) or not. Default is no.

Here's an example of data with two channels, the red of which was despiked and smoothed, as explained below:

Operations

If one or several channels have been selected to be modifyable, we may perform some operations on them to improve the apprearence. For the moment, I have available:

• remove spikes: clicking this button will remove all the narrow spikes. The technique is to check every datum whether it lies above a straight line connecting data width pixels apart; if it does so by more than a factor (1+height) of the current y-value, the datum is replaced by the value predicted by the straight line.
• smooth: is done simply by averaging over the width pixels left and right of each pixel.
• back to Original abandons all changes.

First we remove the spikes:

and then we smooth the curve (once or twice...)

Calibrate

Here we use the calibration sequence to convert the voltages into noise temperatures. This is done interactively: Having chosen a good view of the calibration steps - and it helps to remove spikes and smooth the data, as we did - we

• choose between dB(kT0) if we know the calibration steps in decibel above thermal noise (as we shall do here) or kK if they are known in thousands of Kelvin.
• starting from: enter the value for the maximum step (here: +46 dB(kT0))
• Stepping down by [dB] enter the value in decibels by how much each step is lower than the other (here: 5 dB)
• begin cal. click this, then start at the top most step, click on each calibration step, which then is marked with a blue dot, ...
• end cal. ... when done, click this, and the calibrated plot will be shown
• break-off allows to stop the calibration process at any time

Note that this calibration remains valid for any file loaded afterwards.

At the end, we get this view of the calibrated data, done in dB(kT0) [or in kK if you had chosen it at the start]

Here is a zoomed view in linear temperatures in kK

From this zoom we read off that during the low state of our interference we have about 100 kK - which could be sufficient to pick up Jovian bursts - but 200 kK during the high state!

Cal.Table

Here is a zoomed view of the calibration sequence, shown together with the table which the program constructed from our interactive identification of the calibration steps.

• we may switch between dB(kT0) and kK
• we may alter any of the numerical values manually
• and apply them to the data
• wipe removes the entire table and thus the calibration

This calibration is kept inside the program when you load a new file.

Period

If one has a signal which appears to be periodic, we can measure its period and also check whether it is strictly periodic:

• select the units of time sec or min or longer ...
• enter the suspected period - or better still: twice or thrice that period
• refresh will show the data folded repeatedly into this time interval
• back to full shows the entire time span again

Some hints are necessary here to make life easier with this option: First, in Plot select a zoomed view of the signal to be analyzed. In particular, one has to leave sufficient space in the vertical direction. Then, take the ranges from zoomand put ranges to define the current unzoomed view. Note that if the channel was modified by operations, only the modified signal is shown. Finally, it is generally more sensible to select only one channel for plotting...