[This plot is updated every minute.]

The plot shows the last 24h of observation.  The two prominent, adjacent interference patterns are from (on right) the supernova
remnant Cass A, (situated in our own Galaxy) and (on left) the active galaxy Cygnus A, at a distance  ~1/30th of the way to the 
edge of the Universe.  The Sun also produces a signal whose amplitude can vary greatly from day-to-day, depending on
sunspot activity, as the Sun passes through the antenna sidelobes. (Currently, this signal is superimposed on the
Cygnus/Cass patterns.)

The periodicities of the interference patterns are determined by the declinations of the sources.


Description of the Receiver.
---------------------------

After further amplification by two preamplifiers, the signal from one Yagi aerial is put through a 180 deg switch, combined
with the signal from the other aerial, and fed into a "TV Dongle" tuned to 150.4MHz and plugged into a Raspberry Pi 2.

The Raspberry Pi -
i)    provides the drive waveform for the 180 deg switch;
ii)   uses the TV dongle to sample the signal at 900 ksample/s, converts it to baseband (0-450 kHz), 
      providing 8-bit Cos and Sin samples of the resulting  +-450 kHz bandwidth signal;
iii)  calculates the total power of each sample, both with and without phase-sensitive demodulation;
iv)   integrates both values for ~5s and records the ratio (times 10**4) in a 'round-robin' database;
v)    produces a plot of this ratio for the last 24h period.

The plot is therefore a (scaled) measure of the amplitude of the correlated component in the signals from the two Yagi
antennas.

             The Receiver                                                                                 The two antennas