85-GHz BIMA observations of the double-hotspot radio galaxy 3C 20

We present 85-GHz observations of the archetypal double-hotspot radio sourc e 3C 20 made with the BIMA millimetre array. The resolution of BIMA allows us to separate the two components of the eastern hotspot. By comparing the BIMA observations with existing VLA data, we show that the spectra of the t wo hotspot components are very similar, despite the clear differences in th eir radio structure and their wide separation. We discuss the implications for models of double hotspot formation. Weak emission from the lobes of 3C 20 is detected at 85 GHz, at a level consistent with the predictions of sta ndard spectral ageing models.