  If they exist, networks of superconducting cosmic strings are capable of
injecting copious amounts of electromagnetic energy into the background over a
broad range of frequencies. We study this injection both analytically, as well
as numerically using the thermalization code CosmoTherm. With our refined
analytic formalism, we update constraints from CMB spectral distortions by
following the injection of entropy, as well as energy, on the amplitude of the
$\mu$-distortion, leading to a significant improvement in those limits.
Furthermore, we utilize the full shape of the distorted spectrum from
CosmoTherm to include constraints from non-$\mu$, non-$y$ type distortions.
Additionally, we use the outputs for the ionization history and global 21cm
signal to derive and update constraints on string model parameters using
measurements from other datasets. Analysis of CMB anisotropies provides the
most stringent constraints, though with a slightly modified shape and strength
when compared to previous results. Modifications of the reionization history
provide new bounds in the high current domain, and we also find that the
observations of the low-frequency radio background probe a small region of
parameter space not explored by other datasets. We also analyze global $21$-cm
constraints, and find that the inclusion of soft photon heating plays a crucial
role, essentially removing any constraints in the considered parameter domain.
Spectral distortion measurements from COBE/FIRAS are covered by other
constraints, but our conservative forecast shows that a PIXIE-type satellite
would probe important unexplored regions of parameter space.
