Explanations for SkyPipePlotter Applet

Joachim Köppen DF3GJ Kiel/Strasbourg/Illkirch May 2004


How we start:

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.
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...


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

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


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:

One simply fiddles with these three parameters, until one obtains what one accepts as a nice result...

First we remove the spikes:

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


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

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!


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 could enter manually any calibration point data, such as given by the observer in the file header or the labels.

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


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

The resultant plot shows that the period is close to 47 seconds, but that the pulses do not follow with an exactly constant period. There is some phase jitter ... So it seems unlikely that this signal is produced by a quartz clock or a computer...

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...

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