I also have a Ballentine 1605A. These are quite accurate, reasonably fast, wide frequency response instruments. They're microprocessor controlled and will do automatic measurements so you don't have to do manual nulling. It can also be calibrated against a DC standard, but that doesn't correct for frequency non linearity, of course. The manual is still available from Ballentine (for a silly amount of money). I don't see many of these on FleaBay, though. -- Bill Ezell ---------- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners.