We present the results of a long-look monitoring of 3C 273 with RXTE between 1996 and 2000 .
A total of 230 observations amounts to a net exposure of 845 ksec , with this spectral and variability analysis of 3C 273 covering the longest observation period available at hard X-ray energies .
Flux variations by a factor of 4 have been detected over 4 years , whereas less than 30 \% flux variations have been observed for individual flares on time-scales of \sim 3 days .
Two temporal methods , the power spectrum density ( PSD ) and the structure function ( SF ) , have been used to study the variability characteristics of 3C 273 .
The hard X-ray photon spectra generally show a power-law shape with a differential photon index of \Gamma \simeq 1.6 \pm 0.1 .
In 10 of 261 data segments , exceptions to power-law behaviour have been found : ( i ) an additional soft excess below 4 keV , and ( ii ) a broad Fe fluorescent line feature with EW \sim 100 - 200 eV .
Our new observations of these previously reported X-ray features may imply that 3C 273 is a unique object whose hard X-ray emission occasionally contains a component which is not related to a beamed emission ( Seyfert like ) , but most hard X-rays are likely to originate in inverse Compton radiation from the relativistic jet ( blazar like ) .
Multi-frequency spectra from radio to \gamma -ray are presented in addition to our RXTE results .
The X-ray time variability and spectral evolution are discussed in the framework of beamed , synchrotron self-Compton picture .
We consider the “ power balance ” ( both radiative and kinetic ) between the accretion disk , sub-pc-scale jet , and the 10 kpc-scale jet .