Hardware Hacking

New! Live strip chart data.

Along with the 232Mhz band experiment, I've also identified another band inside the frequency range of my VHF collinear array antenna which is also relatively radio quiet at around 173.5Mhz. However, in this series of observations I will try to set up my scans in such a way that I can also identify where in the sky the antenna is pointed and what would cause the rise and fall of signals recorded.

To do this I have first set-up the antenna using a compass to orient it in a North-South direction. This is so that the antenna can be tilted in ark from North to Zenith to South in order to conduct a meridian drift scan in different parts of the sky, as the earth rotates. In my case I used a simple Protractor to measure Zenith at 90 degrees directly up.

Then using a Level and a Protractor I have first pointed the antenna slightly North at an elevation of 80 degrees North and conducted a 24 hour scan using a software data-logger called Radio-SkyPipe. The result is the following trace in Red.

The time scale on these graphs begin in Adelaide Time February 2010 at 4pm for 24 hours.

I then repeated the scan, beginning at the same time on the next day, but with the antenna re-pointed at an elevation of  80 degrees South recording a different trace seen here below in Blue.  In preparation I for these scans also run several in order to rule out terrestrial interference and although the the peak noise spikes seen in these graph changes, the same overall shape of the 24 hour scan is consistent.  

Then using a program called Radio Eyes which is similar to a optical planetarium program I was then able to plot my location and time; along with the direction, elevation and beam width of the antenna. The program then provides a prediction of radio signals that the antenna could expect to receive at any specific time or date.  The follow is a image is of the sky at radio frequency and has been edited to demonstrate the approximate source locations are in the above scans. Traced as it falls in relation to each.

Red being an elevation of 80 degrees North, and Blue being an elevation of 80 degrees South.