For cable TV investors, this week's challenge is to separate the unexpected disappointments from the expected ones.On Wednesday and Thursday, the nation's three largest operators of cable TV systems are slated to report earnings for the quarter ended June 30. The second quarter has typically been the slowest quarter of the year for cable operators, and this year promises to be no exception. But complicating the expected negatives of basic subscriber losses and slowing gains for advanced services are issues that can't be dismissed as seasonal: competition from satellite in the multichannel video market, and the onslaught of local telcos into the high-speed Internet-access business. Rightly or wrongly, the threat to cable posed by satellite operators and regional Bell operating companies -- both separately and in joint ventures -- has weighed heavily on cable stocks over the past six months. So, with analysts preparing for less-than-blowout quarters in the next few days, investors will have to decide how much seasonality is to blame -- and whether there's any reason to hope that the turnaround of cable stocks has arrived. Kicking off the reporting season Wednesday morning will be Comcast ( CMCSA), the nation's largest operator of cable TV systems, and Time Warner ( TWX), the multimedia conglomerate that's the operator of the second-largest group. Cox ( COX), the country's third-largest cable operator, reports Thursday morning, and Insight ( ICCI), a top 10 operator, posts its numbers Friday morning. Shares of all four companies have suffered this year amid a sustained cable-sector selloff. On Friday, Comcast closed at $27.99, Time Warner at $16.94, Cox at $27.66 and Insight at $8.60.