  The 2004 December 27 giant flare from SGR 1806-20 produced a radio nebula
that was detectable for weeks. It was observed at a wide range of radio
frequencies. We made a total of 19 WSRT observations. Most of these were
performed quasi simultaneously at either two or three frequencies, starting
2005 January 4 and ending 2005 January 29. We reobserved the field in 2005
April/May, which facilitated an accurate subtraction of background sources.
  At 350 MHz, we find that the total intensity of the source is lower than
expected from the GMRT 240 MHz and 610 MHz measurements and inconsistent with
spectral indices published previously. Our 850 MHz flux densities, however, are
consistent with earlier results. There is no compelling evidence for
significant depolarization at any frequency. We do, however, find that
polarization angles differ substantially from those at higher frequencies.
  Low frequency polarimetry and total intensity measurements provide a number
of clues with regard to substructure in the radio nebula associated with SGR
1806-20. In general, for a more complete understanding of similar events, low
frequency observations can provide new insights into the physics of the radio
source.
