  We study the intensity, the modulation depth and the mean modulation depth of
the gyrosynchrotron (GS) radiation as a function of the frequency and the line
of sight (LOS) in fast sausage modes. By solving the 2.5D MHD ideal equations
of a straight coronal loop considering the chromosphere and with typical
flaring plasma parameters we analyse the wavelet transform of the density and
the GS emission for different radio frequencies and different spatial
resolutions, given impulsive and general perturbations with energies in the
microflare range. A wavelet analysis performed over the GS radiation emission
showed that a fast fundamental sausage mode of 7s with a first harmonic mode of
3s developed, for all the initial energy perturbations used. For both the high
spatial resolution (central pixel integration) and the low spatial resolution
(entire loop integration), the larger the radio frequency, the larger the
modulation depth. However, high and low resolution integrations differ in that,
the larger the LOS angle with respect to the loop axis, results in a larger and
smaller modulation depth, respectively. Fast MHD modes triggered by
instantaneous energy depositions of the order of a microflare energy are able
to reproduce deep intensity modulation depths in radio emission as observed in
solar events. As the trends of the GS emission obtained by Reznikova, Antolin,
and Van Doorsselaere (2014), for a linear and forced oscillation, remain
present when analysing a more general context, considering the chromosphere and
where the sausage mode is triggered by a impulsive, nonlinear perturbation, it
seems that the behaviour found can be used as observational identifiers of the
presence of sausage modes with respect to other quasi-periodic pulsation
features. It can be inferred from this that finite-amplitude sausage modes have
the potential to generate the observed deep modulation depths.
