Qualstar Corp. narrowed its adjusted net loss in the fiscal second quarter while reporting a decrease in revenue. The Simi Valley manufacturer of tape storage and power supply products announced a net loss of $336,000 (-16 cents a share) for the quarter ending June 30, compared with a net loss of $254,000 (-12 cents) in the same period a year earlier. Revenue fell 27 percent to $2.4 million. No analysts follow the company. Chief Executive Steven Bronson said that excluding non-recurring expenses, the net loss for the quarter was $75,000. “We are encouraged by the ongoing reduction in our net loss, and remain confident in our ability to return the company to profitability once our restructuring efforts are complete,” Bronson said in a prepared statement. Qualstar released its earnings on Thursday. Shares closed Friday up 19 cents, or more than 4 percent, to $4.59 on the Nasdaq. BNK Petroleum reported wider losses as the price of oil remained volatile in the second quarter. The Camarillo oil producer on Friday announced a net loss of $5.3 million (-3 cents a share) during the quarter ended June 30, compared to a loss of $3.3 million (-2 cents) for the same quarter a year ago. Revenue fell 40 percent to $2.4 million. No analysts follow the company. Shares closed unchanged at 20 cents on the over-the-counter market.