Interferometer phase calibration sources - I. The region 35deg <= Dec. <= 75deg.

We present a catalogue of 800 compact radio sources in the declination range 35^deg^<= δ <= 75^deg^ whose positions have been measured to an rms accuracy of ~12 milliarcsec with the VLA. They are primarily intended for use as phase reference sources for the Jodrell Bank MERLIN but they will also be suitable phase calibrators for the VLA and the VLBI networks.