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

The Latest from the Hydrogen Line Observing group can be downloaded from here as a pdf.

The Redenham Radio Telescope




The 3.7 Metre dish Antenna at G4NNS Click the picture to see a larger photo. The 3.7 Metre dish Antenna on its new Azimuth and Elevation mount. Click the picture to see an explaination of its design and construction The tracking software developed with G8APZ. Click on the picture for more details and a larger picture.





Listen to Echoes from Meteor Trails

The signal is coming from the Graves RADAR near Dijon a distance of about 670Km from Redenham and 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.The audio spectrogram is from the recording you can play by pressing the start buton on the recorder icon above.
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.
Hydrogen Line Astronomy
by the Hydrogen Line Observing Group

Hydrogen emits radiation at 1420.405752MHz a wavelength of 21cm in the microwave L-Band and being the most abundant element in the universe it provides a very useful means of measuring relative velocity. When the source of radiation is moving relative to the observer it is Doppler shifted from the “rest frequency”. The above plot shows signal level, equivalent to brightness, as the vertical scale and radial velocity as the horizontal scale, derived from the Doppler equation. This observation was made "looking" in the plane of the our galaxy, the Milky Way, across its spiral arms towards Cygnus. The are three peaks due to there being three “bodies” of Hydrogen contained in the spiral arms of the galaxy. As planet earth has a different velocity relative to each arm, three peaks appear in this scan. The largest peak is from radiation in the local Orion arm with the next peak being radiation from the Perseus Arm and the right hand peak from the Cygnus arm. This plot shows the observation data from the Hydrogen Line Observing Group, using the Redenham Telescope in blue with the predicted spectra from the LAB survey (University of Bonn) in Red



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