THREE SPEED PHILLIPS TAPE RECORDER
Surface ships were able to copy the Navy's main radio broadcast continuously on
a 24-hour basis. However, for a submarine to copy the Navy's main radio
broadcast, he had to be on the surface or at periscope depth with the radio mast
raised above the surface. Most of the time, submarines could not copy the radio
broadcast because they were submerged below periscope depth. Therefore submarine
radio traffic using morse code was sent during specific submarine schedules
every four hours. It was up to the submarine Captain to decide when to go up to
receive radio traffic. Depending on the operational exercise, he sometimes
decided to wait for the next schedule thus taking the risk of missing messages
adressed to the submarine. Each message to submarines had a serial number and
was sent on four separate submarine schedules. So up to three schedules could be
missed without missing any messages. Sometimes, four or five schedules were
missed due to operational requirements but it was still OK if there had been no
new messages on the first two missed schedules. However, there were messages
being missed on occasions and a request had to be sent to the shore station to
have the missed messages resent again. When this happened, the missed messages
were sent again on the next four schedules.
Every 4 hours, the radio sparker on duty
reported to the control room that the next radio schedule was coming up in
30 minutes. If it was decided to go up and copy the radio traffic, the radio
sparker got ready by tuning his receiver in advance and preparing the tape
recorder. As soon as the submarine arrived at periscope depth, the radio
mast was raised and the radio sparker did the final tuning of his receiver.
When it was time to
begin the submarine radio schedule, surface ship radio traffic being sent at
22 words per minute was stopped by the shore station. Submarine radio
traffic would then begin in morse code at 100 words per minute.
When submarine radio traffic was over, the shore station returned the navy's main radio broadcast to
surface ship radio traffic at 22 words per minute.
A tape recorder similar to the one above was used onboard submarines to record
the submarine morse code radio traffic at 100 words per minute.
When all submarine radio traffic had been recorded the submarine would quickly return
below periscope depth.
After the submarine had returned to the deep, Radiomen lowered the speed of the
tape recorder to copy the messages. Morse code recorded at 100 words per minute
was reduced to
25 words per minute for easy copying on a typewriter.
It was important to record the CW signal at high pitch.
It made it easier to copy the messages because the slower speed drastically
reduced the pitch.
It should be noted that most radio traffic
was classified and had to be encrypted. An in-line crypto machine, the
KWR-37 mentioned earlier, was used for radioteletype traffic, but morse code
traffic was a lot more work since it had to be manually encrypted into
5-letter groups and decrypted back into plain language using the KL-7 crypto
machine. It was a lot more work for radiomen, and a lot slower process.