  We present radio observations of the magnetic chemically peculiar Bp star HR
Lup (HD 133880) at 647 and 277 MHz with the GMRT. At both frequencies the
source is not detected but we are able to determine upper limits to the
emission. The 647 MHz limits are particularly useful, with a 5\sigma\ value of
0.45 mJy. Also, no large enhancements of the emission were seen. The
non-detections, along with previously published higher frequency detections,
provide evidence that an optically thick gyrosynchrotron model is the correct
mechanism for the radio emission of HR Lup.
