The following link has some good info:
http://uboat.net/technical/detectors.htm
I know the "Metox transmitting detectable signals" versus the "Lie told by captured British officer" has been tossed around the forum for a while. I think the general consensus is that it was the introduction of 10cm radar (undetectable at the time by German technology) that was the cause of so many losses of 1943 instead of the Metox transmitting signals.
Thanks,
Ron