  We present 85-GHz observations of the archetypal double-hotspot radio source
3C20 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 two
hotspot components are very similar, despite the clear differences in their
radio structure and their wide separation. We discuss the implications for
models of double hotspot formation. Weak emission from the lobes of 3C20 is
detected at 85 GHz, at a level consistent with the predictions of standard
spectral ageing models.
