The Energy Spectrum of a Radio Pulse Created by a Cascade Disk Within   the Moon's Regolith
  Some known analytical solutions for a cascade shower were used for determining the intensity of excess electrons' radio-emission. It is shown that the energy spectrum has a sharp decline in the region of high frequencies. At a usual root-mean-square radius of the disk within the Moon's regolith ~ 0.06m the maximum of the spectrum is in the region ~ 0.5-0.6 GHz while in the range 2-2.5 GHz the pulse's amplitude drops by 5-6 orders. This fact is a consequence of loss of coherence due to finite dimensions of the cascade disk and demands conducting a significant correction of "radio-frequency window" for measuring cosmic rays' flux with a radio telescope. 
Anatoliy D. Filonenko, Evgeniy V. Nikitin
astro-ph.HE