G4NNS
Amateur Radio Astronomy
located 51 14'53.1N 1 34'15.6W

Listen to Echoes from Meteor Trails


The signal is coming from a VHF transmitter at a distance of about 1400Km which is far beyond the normal Radio Horizon. As the meteors burn up they leave trails of ionised material that briefly reflect the radio signals. Sometimes the Pitch of the received signal changes due to Doppler shift as the centre of reflection moves rapidly across the sky.

Listen to VHF Radio signals reflected from the Aurora


Again this signal is from far beyond the normal Radio Horizon, coming from DL1EAP in Germany. Also,it has arrived at G4NNS from the North having been reflected from the Aurora. The rough note of this CW (Morse) signal is due to the loss of coherency caused by reflection from the auroral curtain which does not behave like a reflector with a plane surface. Reflections from different parts of the “curtain” reach the receiver at slightly different times.

Listen to the Crab Pulsar


When all its fuel has been “burnt” in Nuclear Fusion, stars with a mass much greater than our sun explode in a Super Nova sending about half their material out into space and causing the other half to collapse and become a Neutron Star. A typical mass for a Neutron Star is 2-3 times that of the sun but this is compressed into a space of only about 20Km in diameter and thus has an incredibly high density of millions of tonnes per cubic centimetre. In the process of collapse, angular momentum is conserved causing the Neutron star to spin many times faster than its “parent” in the same way that a ballerina increases her rate of spin when she draws in her arms. Neutron stars have very strong magnetic fields and emit large numbers of electrons and charged particles at speeds approaching that of light. These spiral in the magnetic fields and give rise to Synchrotron radiation at radio frequencies beamed out from the magnetic poles. If the axis of the magnetic field is offset from the axis of spin, this gives rise to a beam of radio energy sweeping around as the neutron star spins. The explosion of the Crab was observed by Chinese astronomers in 1054 and has given rise to the Crab Nebula and Pulsar. The Crab Pulsar is about 6500 light years away in the constellation Taurus and rotates about 30 times per second. This recording was not made at G4NNS.

To view an image of the Crab Pulsar courtesy of APOD Click Here Use the Back button to return to this page.

See also The G4NNS Web Cam Astronomy Page

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