sentences:  Intelligence reports in July indicated that U-boats were using the Faeroes-Iceland passage, so a series of deep anti-submarine fields were laid north-west of the Faeroes.A refitting programme in U.S. ports was implemented in 1941, but work was delayed by fog and gales.1942 minelaying used a new Mk XXII mine with a buoyant copper tube upper antenna replacing the solid copper wire and buoyant float of the Mk XX mines.