  In this paper we address some of the properties of quantum Hall line
junctions (QHLJ) that occur near barriers separating electron gases on quantum
Hall plateaus.In narrow barriers where electron tunneling can occur, the low
energy physics of the QHLJ is described by the quantum sine-Gordon model. We
propose procedures to study a sort of properties of these systems in relation
with recent experimental studies of Kang {\it et al.}, Nature {\bf 403}, 59
(2000). We propose experimental ways of measuring the values of the
dimensionless coupling constant characteristic for the Sine-Gordon model as
well as its Fermi velocity. When the bulk filling of the 2DEG subsystems is
$\nu \sim 2$, these systems can be good candidates for observation of
spin-incoherent LL behavior.
