How to setup the Receiver and the Software

Joachim Köppen DF3GJ Kiel/Strasbourg/Illkirch Summer 2004

When the receiving station is first set up, check whether the use of the narrow band filter is needed: Listen to the audio output for any signs of music or speech transmission which are present irrespective of the setting of the tuning control (right hand knob). But you must check at several times of the day, and for a couple of days, because the ionospheric conditions - which cause strong short wave broadcast signals - change appreciably!

If you need to use the filter, you should convince yourself that the filter is optimally tuned (it might have changed due to the transport!):

• turn on the calibrator, use maximum noise, and switch from antenna to calibrator. Set the receiver tuning control in the 12 o'clock position, i.e. in the centre of the tuning range. Listen to the audio output and observe the tracing on the SkyPipe chart
• slowly and gently turn the screws of the trimmer capacitors in either way, until you get a maximum noise output. Note that the trimmers come in two pairs acting in parallel. Use the one whose screw is sticking more our than the other.
• Change the receiver tuning to both ends of the range. The noise level should fall off somewhat towards the ends, preferably in the same amount to either side. If this is so, the filter's pass band is centered on the middle of the receiver's tuning range
• If not, adjust the trimmers a bit more, until you get an almost symmetrical fall-off of the noise.
• The filter tuning might change due to mechanical handling and strong temperature changes. After placing in position at the receiving station, it may need a bit of time to relax. This means that in the first few days the filter's passband might drift a little off the frequency of the receiver, and thus the receiver will get less signal...
• To check this, we simply use the receiver I sent from Strasbourg, operating it for the first few daya, and making regular calibrations. If one notices that the audio amplitudes for the various calibration steps change systematically and significantly (say, by more than 3 to 5 percent), we have to retune the filter a bit.
• But once settled and tuned properly, the filter remains stable over months! This is our experience at ISU

The Radio-SkyPipe software has to be configured to suit your needs ( Help pages are here): In the Options menu

• submenu Identity enter the details of your station and set the correct time zone
• submenu Stripchart: set data sampling and averaging rate. At ISU we use:
  • sample period (stand alone): 1 ms (default value is 10 ms)
  • averaging (stand alone): over 50 samples (default value is over 5 samples)
  • I found our present setting more suitable than the default one; we do not loose significantly in the data, but one can store about 3.5 hours in a file with 50000 data points. The data volume is about 30 MB/day (with default options), and only about 6 MB/day with the higher averaging. I think one could go even higher in averaging without losing much. One needs to try ... I find that with averaging over 100 samples some interesting information is lost (30 june 2004)
  Also, you can influence how the plot is being done (setting the your default value for the maximum ordinate, and the number of ticks on the axes, the colour of the tracing, etc)
• submenu Logging: specifiy that you want to use UT, give maximum duration or maximum file size (I use 50000 samples which gives files of about 800 kB size), and whether you want to restart the chart at a specific time (I use 00:00 UT).