  Blazar spectral models generally have numerous unconstrained parameters,
leading to ambiguous values for physical properties like Doppler factor delta
or fluid magnetic field B'. To help remedy this problem, a few modifications of
the standard leptonic blazar jet scenario are considered. First, a log-parabola
function for the electron distribution is used. Second, analytic expressions
relating energy loss and kinematics to blazar luminosity and variability,
written in terms of equipartition parameters, imply delta, B', and the
principal electron Lorentz factor gamma'_pk. The external radiation field in a
blazar is approximated by Ly alpha radiation from the broad line region (BLR)
and ~0.1 eV infrared radiation from a dusty torus. When used to model 3C 279
SEDs from 2008 and 2009 reported by Hayashida et al. (2012), we derive delta ~
20-30, B' ~ few G, and total (IR + BLR) external radiation field energy
densities u ~ 0.01 - 0.001 erg/cm^3, implying an origin of the gamma-ray
emission site in 3C 279 at the outer edges of the BLR. This is consistent with
the gamma-ray emission site being located at a distance R <~ Gamma^2 c t_{var}
~ 0.1 (\Gamma/30)^2 (t_{var}/10^4 s) pc from the black hole powering 3C 279's
jets, where t_{var} is the variability time scale of the radiation in the
source frame, and at farther distances for narrow-jet and magnetic_reconnection
models. Excess >~ 5 GeV gamma-ray emission observed with Fermi LAT from 3C 279
challenge the model, opening the possibility of hadronic origins of the
emission. For low hadronic content, absolute jet powers of ~10% of the
Eddington luminosity are calculated.
