  We calculated the coupled channel photoproduction amplitudes of the scalar
isovector resononace $a_0(980)$, which include the $\pi\eta$, $K^+K^-$ and
$K^0\overline{K^0}$ intermediate states. Based on them we obtained the mass
distribution in the $\pi\eta$ channel at photon energy $E_\gamma$=7 GeV,
corresponding to energy accissible in new JLab experiments CLAS12 and GlueX. We
also analyzed the shape of mass distribution as a function of the phase of the
background amplitude.
