[Milsurplus] R-3 on U-boats

[Hubert Miller]

Here is some text I copied from a militaria dealer website:

"The Radione R3 is a WWII-era portable communications receiver also used for troop entertainment.
It was used by all services, including U-Boats. It runs on a variety of voltages and has a BFO for CW reception.
More information can be seen here. At one point in WWII the Germans thought that U-boats were being located
by emissions from radio receivers and issued an order (later rescinded) to turn off and not use these radios. "

I'd never read about this order anywhere else. Anyone know the dates, even if approximate? If I had to guess, I 
would say the order was promulgated summer of '43, which was a very bad one for the U-boats.
-Hue