  Recent measurements of gamma rays from the powerful quasar 3C273 by the
Compton Gamma Ray Observatory show that a powerful cosmic accelerator must be
operating. In this paper the evidence for proton acceleration is collected with
the result that (i) the gamma ray spectrum should flatten slightly above a few
GeV and that (ii) high energy neutrinos from the decay of photomesons are
difficult to observe, although the power carried by these particles is as large
as the gamma ray power. However, the power is concentrated at energies in the
EeV range, whereas in the TeV-PeV range neutrinos from pp and p$\alpha$
collisions dominate due to their steeper spectrum. Consequently, the flux of
cosmic neutrinos from flat spectrum radio sources such as 3C273 in the energy
range relevant for proposed underwater or underice detectors could be much
lower than inferred from assuming the same spectrum for gamma rays and
neutrinos.
