On Mon, 07 Nov 2011 10:14:14 +0100, Szczepan Bialek rearranged some
electrons to say:

"The first observations of cosmic radio emission were made by the
American engineer Karl G. Jansky in 1932, while studying thunderstorm
radio disturbances at a frequency of 20.5 MHz (14.6 m). He discovered
radio emission of unknown origin, which varied within a 24-hour period.
Later he identified the source of this radiation to be in the direction
of the centre of our Galaxy. From:
http://encyclozine.com/science/astronomy/radio

I understand that the frequency "varied within a 24-hour period". It is
the "diurnal effect".
And what about the 365 days period (annual effect)?
S*

It is not the frequency that changed, but the intensity. And not a 24
hour period, but 23 hours, 56 minutes, thus proving that the noise was
not generated or varied by the earth's rotation.

http://www.enotes.com/karl-jansky-reference/karl-jansky