  We construct a simple analytical model to study the effects of cosmic strings
on the microwave background radiation. Our model is based on counting random
multiple impulses inflicted on photon trajectories by the string network
between the time of recombination and today. We construct the temperature
auto-correlation function and use it to obtain the effective power spectrum
index n, the rms-quadrupole-normalized amplitude $Q_{rms-PS}$ and the rms
temperature variation smoothed on small angular scales. For the values of the
scaling solution parameters obtained in Refs.\cite{bb90},\cite{as90} we obtain
$n=1.14 \pm 0.5$, $Q_{rms-PS}=(4.5\pm 1.5) G\mu$ and $({{\Delta T}\over
T})_{rms}=5.5 G\mu$. Demanding consistency of these results with the COBE data
leads to $G\mu=(1.7 \pm 0.7)\times 10^{-6}$ (where $\mu$ is the string mass per
unit length), in good agreement with direct normalizations of $\mu$ from
observations.
