  Protostellar jets are one of the primary signposts of star formation. A
handful of protostellar objects exhibit radio emission from ionized jets, of
which a few display negative spectral indices, indicating the presence of
synchrotron emission. In this study, we characterize the radio spectra of
HH80-81 jet with the help of a numerical model that we have developed earlier,
which takes into account both thermal free-free and non-thermal synchrotron
emission mechanisms. For modeling the HH80-81 jet, we consider jet emission
towards the central region close to the driving source along with two
Herbig-Haro objects, HH80 and HH81. We have obtained the best-fit parameters
for each of these sources by fitting the model to radio observational data
corresponding to two frequency windows taken across two epochs. Considering an
electron number density in the range $10^3 - 10^5$ cm$^{-3}$, we obtained the
thickness of the jet edges and fraction of relativistic electrons that
contribute to non-thermal emission in the range $0.01^{\circ} - 0.1^{\circ}$
and $10^{-7} - 10^{-4}$, respectively. For the best-fit parameter sets, the
model spectral indices lie in the range of -0.15 to +0.11 within the observed
frequency windows.
