  We report results of a serendipitous hard X-ray (3--20 keV), nearly all-sky
(|b|>10deg) survey based on RXTE/PCA observations performed during satellite
reorientations in 1996--2002. The survey is 80% (90%) complete to a 4$\sigma$
limiting flux of ~1.8 (2.5) e-11 erg/s/cm2 in the 3--20 keV band. The achieved
sensitivity in the 3--8 keV and 8--20 keV subbands is similar to and an order
of magnitude higher than that of the previously record HEAO-1 A1 and HEAO-1 A4
all-sky surveys, respectively. A combined 7000 sq. deg area of the sky is
sampled to flux levels below 1e-11 erg/s/cm2 (3--20 keV). In total 294 sources
are detected and localized to better than 1 deg. 236 (80%) of these can be
confidently associated with a known astrophysical object; another 22 likely
result from the superposition of 2 or 3 closely located known sources. 35
detected sources remain unidentified, although for 12 of these we report a
likely soft X-ray counterpart from the ROSAT all-sky survey bright source
catalog. Of the reliably identified sources, 63 have local origin (Milky Way,
LMC or SMC), 64 are clusters of galaxies and 100 are active galactic nuclei
(AGN). The fact that the unidentified X-ray sources have hard spectra suggests
that the majority of them are AGN, including highly obscured ones (nH>1e23
cm^{-2}). For the first time we present a logN-logS diagram for extragalactic
sources above 4e-12 erg/s/cm2 at 8-20 keV.
