Simultaneous multifrequency observations of the Crab pulsar giant pulses ( GPs ) were performed with the 64-m Kalyazin radio telescope at four frequencies \nu = 0.6 , 1.4 , 2.2 and 8.3 GHz , using the K5 VLBI recording terminal .
The K5 terminal provided continuous recording in 16 4-MHz wide frequency channels distributed over 4 frequency bands .
Several thousand GPs were detected during about 6 hours of observations in two successive days in July 2005 .
Radio spectra of single GPs were analysed at separate frequencies and over the whole frequency range .
These spectra manifest notable modulation over frequency ranges , \Delta \nu , both on large ( \Delta \nu / \nu \approx 0.5 ) and small ( \Delta \nu / \nu \approx 0.01 ) frequency scales .
Cross-correlation analysis of GPs at 2.2 GHz showed that their pulse shapes can be interpreted as an ensemble of unresolved bursts grouped together at time scales of \approx 1 ~ { } \mu s being well-correlated over a 60-MHz band .
The corresponding GP cross-correlation functions do not obey the predictions of the amplitude-modulated noise model of \citet Rickett75 , thus indicating that unresolved components represent a small number of elementary emitters .