The 6C survey of radio sources - I. Declination zone delta > +80.

The 6th Cambridge Survey of radio sources covers most of the sky north of delta +30 deg with an angular resolution of 4.2 x 4.2 cosec delta sq arcmin and a limiting flux density of 120 mJy at 151 MHz. This paper, the first of a series, describes the telescope and the methods used to produce the survey maps and source list, and presents maps of a circular area of radius 10 deg centered on the North Celestial Pole and a list of 1761 sources north of delta +80 deg.