  We present images of the SNR HB3 at both 408 MHz and 1420 MHz from the
Canadian Galactic Plane Survey mainly based on data from the Synthesis
Telescope of the Dominion Radio Astrophysical Observatory. We reproduce the
100m-Effelsberg HB3 image at 2695 MHz at large scale, and find that there
exists a background emission gradient across the HB3 area. Based on our
analysis of background emission and the boundary between W3 and HB3, we give
HB3's flux density as 68.6 +/- 11.5 Jy at 408 MHz and 44.8 +/- 12.0 Jy at 1420
MHz, after subtracting flux from compact sources within HB3. The integrated
flux-density-based spectral index between 408 MHz and 1420 MHz is 0.34 +/-
0.15. The averaged T-T plot spectral index using all subareas is 0.36. Our
measurement values are less than a previously published value of 0.6. The
408-1420 MHz spectral index varies spatially in HB3 in the range 0.1 to 0.7. We
investigate the data used by previous authors, and consider more data at 232
MHz, 3650 MHz and 3900 MHz which are not included in previous calculations.
There is evidence for two spectral indices for HB3 in the radio band, i.e.,
0.63 (38 - 610 MHz) and 0.32 (408 - 3900 MHz). This is consistent with the
spatial variations: the low frequency data mainly reflects the steeper indices
and the high frequency data mainly reflects the flatter indices.
