Scottish broadcaster STV said it has seen a strong start to 2010, with ad revenues picking up, but remains cautious about the second half of the year.The group also announced plans to sell Pearl and Dean to Image Limited for £1 on a cash free, debt free basis as it refocuses on its main TV business. While its core business continues to trade in line with the company expectations, it remains cautious about the second half of 2010, with uncertainty surrounding the outcome of the General Election and with visibility remaining very short term. The advertising market is forecast to be up 21% in April and up 23% in May with preliminary indications for June showing 10% to 20% growth on 2009, STV said.During the first quarter, STV said national TV airtime revenues were up 17% on last year, with the regional TV airtime market up 4%.