  We present new Ryle Telescope (RT) observations of the Sunyaev Zel'dovich
(SZ) decrement from the cluster Abell 773. The field contains a number of faint
radio sources that required careful subtraction. We use ASCA observations to
measure the gas temperature and a ROSAT HRI image to model the gas
distribution. Normalising the gas distribution to fit the RT visibilities
returns a value of H_0 of 77 (+19,-15) km/s/Mpc (1-sigma errors) for an
Einstein-de-Sitter universe, or 85 (+20,-17) km/s/Mpc for a flat model with
Omega_Lambda = 0.7. The errors quoted include estimates of the effects of the
principal errors: noise in the SZ measurement, gas temperature uncertainty, and
line-of sight depth uncertainty.
