@Leitender: The following I found in Wikipedia (ok, I know it's not the ultimate reference):

"Bis Ende 1942 wurde das Gerät mit gutem Erfolg verwendet, versagte dann aber immer häufiger, da die alliierten Ortungsanlagen auf Dezimeterwellen
umgestellt wurden." = Metox was successfully used until end of 1942......

That was the reason for me to increase the failure probability to 50% from Nov. 42.

By the way: For my private use I plan to assign a failure probability to all german RWR, not only Metox and Naxos, in order to model system failures, malfunctions and thus make aircraft more dangerous and the game more surprising.

Any idea about halfway appropriate failure probabilities?

Concerning allied techniques, i would prefer native "allied" sites. E.g.

http://jproc.ca/sari/sarrad1.html

http://www.vectorsite.net/ttradar_2.html

The introduction dates correspond to the changing numbers of U-boat and allied ship losses. "Ende 1942" is a time period about which i didn´t read anything important - concerning the battle of the beams. Maybe anyone else can help us to find out what happened at the end of 1942?