  The Galactic black hole candidate X-ray binary GX339-4 spends most of its
time in the low/hard state, making it an ideal candidate for modeling the
assumedly low accretion phase. The radio emission correlates very tightly with
the X-rays over more than two orders of magnitude in X-ray flux density,
suggesting that the jet plasma also plays a role at higher frequencies. We
compare the predictions of our jet model, with and without acceleration, to
thirteen broadband simultaneous or quasi-simultaneous spectra over this
changing flux history. In addition, we consider a simple standard thin disk
which transitions to an optically thin accretion flow, in order to account for
the assumedly thermal optical data seen in some observations. A solution
without acceleration cannot describe the data without unrealistic energy
requirements. But because of the low disk luminosity, and possibly the assumed
disk geometry, acceleration in the jet is limited only by synchrotron cooling
and can extend easily into the X-rays. We present a model which can account for
all the broadband spectra included here, by changing only two parameters in the
jet model: the input power and the location of the first acceleration zone.
However, the model is most sensitive to changes in the jet power, the varying
of which can also account for the slope of the observed radio/X-ray correlation
analytically. At the highest low/hard state luminosities, the synchrotron
self-Compton emission from the jet could be detectable with missions such as
{\em GLAST}, providing a way to test the extent of the synchrotron
contribution. We conclude that jet synchrotron is a possible way to explain the
broadband features and this correlation, and discuss ways of incorporating this
component into the ``standard'' corona picture.
