  High-energy cosmic ray air-showers have been known for over 30 years to emit
strong radio pulses in the regime between a few and several 100 MHz (Allan
1971). To date, however, a thorough analysis of the emission mechanisms has not
yet been conducted. Adopting a simplified shower geometry and electron-positron
energy distribution, we calculate theoretical pulse spectra in the scheme of
synchrotron emission from highly relativistic electron-positron pairs gyrating
in the Earth's magnetic field. These calculations will play an important role
for the calibration of observational data of radio-emission from cosmic ray
air-showers acquired with LOPES and later LOFAR and SKA.
