  We analyze the spectral stability of small-amplitude, periodic,
traveling-wave solutions of a Boussinesq-Whitham system. These solutions are
shown numerically to exhibit high-frequency instabilities when subject to
bounded perturbations on the real line. We use a formal perturbation method to
estimate the asymptotic behavior of these instabilities in the small-amplitude
regime. We compare these asymptotic results with direct numerical computations.
This is the second paper in a series of three that investigates high-frequency
instabilities of Stokes waves.
