  A substantial fraction of quasars display broad absorption lines (BALs) in
their rest-frame ultraviolet spectra. While the origin of BALs is thought to be
related to the accretion disc wind, it remains unclear whether the observed
ratio of BAL to non-BAL quasars is due to orientation. We conducted
observations of 48 BAL quasars and the same number of non-BAL quasars at 322
MHz using the Giant Metrewave Radio Telescope. Combined with previous flux
measurements ranging from MHz to GHz frequencies, we compared continuum radio
spectra between the two quasar groups. These data offer insights into
low-frequency radio properties that have been difficult to investigate with
previous observations only at GHz frequencies. Our results present that
$73\pm13$ per cent of the BAL quasars exhibit steep or peaked spectra, a higher
proportion than $44 \pm 14$ per cent observed in the non-BAL quasars. In
contrast, there are no discernible differences between the two quasar groups in
the radio luminosity, peak frequency, and spectral index distributions of
sources with steep or peaked spectra and sources with flat or inverted spectra.
Generally, as the jet axis and line of sight become closer to parallel, quasars
exhibit flat or inverted spectra rather than steep or peaked ones. Therefore,
these results suggest that BAL quasars are more frequently observed farther
from the jet axis than non-BAL quasars. However, given that a certain
proportion of BAL quasars exhibit flat or inverted spectra, more than the
simple orientation scenario is required to elucidate the radio properties of
BAL quasars.
