[Milsurplus] RAK Question

[Tom Brent]

In response to Robert's posting..........

The CNM-47367 coupling unit has a 3 position bandswitch labeled "FREQUENCY 
BAND KILOCYCLES" and marked in ranges of 15-25, 25-43.5 and 43.5-77.5. 
Similar to the RAK/RAL receivers, the tuning dial is not marked directly in 
frequency and the front panel has a small tuning chart holder. My unit 
appears to be unused and the tag bears the serial number 215. I have heard 
of 3 or 4 more of these coupling units in the last 15 years.

What would a submarine have used this loop for at such low frequencies?

TB
._._.