By definition, a radio broadcast is a unidirectional wireless transmission over radio waves intended to reach a wide audience. In other words, a broadcast is a transmission from one station to multiple stations. When two stations are communicating with each other on radio, they are not broadcasting. They are simply transmitting to each other.

In the civilian world, a broadcast is intended to reach the general public. We have AM radio broadcasts, FM radio broadcasts and television broadcasts to disseminate information to the public at large.

In the Navy, back in the 1960s, we had the naval broadcast to send radio messages to the fleet at sea. All ships had to copy the naval broadcast continuously on a 24-hours basis. Submarines below periscope depth could not copy the naval broadcast on a continuous basis so messages addressed to submarines were sent on special submarine schedules every 4 hours.

The naval broadcast for message traffic was transmitted in two modes; morse code (CW) (A1) and teletype (RATT) (F1). There was also a third mode, facsimile, which was used to send weather maps.

On the east coast, the naval broadcast was transmitted from the CFH transmitting site located at Newport Corner near Windsor, Nova Scotia. The Radiomen who remotely controlled the naval broadcast were located 90 kilometers away at the CFH receiving site at Mill Cove near Hubbards, Nova Scotia. Before 1967, the CFH receiving site was located at Albro Lake near Halifax, Nova Scotia but the site had to be moved to Mill Cove due to radio interference near the city of Halifax.

On the west coast, the naval broadcast was transmitted from the CKN transmitting site located at Matsqui, British Colombia. The Radiomen who remotely controlled the naval broadcast were located 20 kilometers away at the CKN receiving site located at Aldergrove, British Columbia.

The east coast CFH naval broadcast and the west coast CKN naval broadcast were two completely separate broadcasts. Canadian ships and submarines at sea copied either one or the other. So messages addressed to a specific ship or submarine were sent on the appropriate broadcast and not on both. However, when it was time to send ship-to-shore traffic, it was not unusual to contact the other coast when ionospheric conditions made it difficult to communicate with your own coast.

The morse code and teletype broadcasts originating from the same station did not have the same content. The teletype broadcast operated at 100 words per minute and there was no need for manually decryptimg classified messages. This was all done automatically. The morse code broadcast operated at 22 words per minute (with the exception of the submarine schedules which operated at 100 words per minute) and classified messages had to be decrypted manually. So the teletype broadcast was able to handle a lot more traffic. The shore station knew which broadcast was being copied by individual ships and submarines so messages addressed to them were sent on the appropriate broadcast.

To make sure that ships and submarines could receive the naval broadcast at all times, it was transmitted simultaneously on multiple frequencies throughout the HF band.  The naval broadcast was also sent on LF for ships and submarines  within a few hundred kilometers which were able to copy ground waves better than sky waves. No matter which frequency was used to receive the naval broadcast, the content was the same.

In the late 1960s, most surface ships were copying the teletype broadcast because it was faster and required less work to handle classified messages. ( see the info on the KWR-7 on the equipment page ). But some ships still copied the morse code broadcast containing encoded classified messages in 5-letter groups  ( see the info on the KL-7 on the equipment page ).

Submarines also copied both the teletype and morse code broadcast when at periscope depth or on the surface. When the radio mast was raised for a long periods of time, like during snorkeling or on the surface, teletype was the preferred mode to copy the submarine schedule. But when time was of the essence and the submarine went up to periscope depth for the sole purpose of copying the submarine schedule, morse code was the preferred mode. Synchronising the teletype crypto gear took too long while the Captain was waiting to return quickly below periscope depth. Morse code was quick and easy when sneaking up to periscope depth for the submarine schedule.

At the shore station, perforated Wheatstone tapes were used to send the morse code broadcast at 22 words per minute. Perforated Baudot tapes were used to send the teletype broadcast at 100 words per minute.

When there was no shore-to-ship radio traffic being sent on the morse code broadcast, the transmission was maintained by using a continuous Wheatstone tape loop containing the call sign and the NATO area covered by the shore station. A continuous transmission was necessary because the naval broadcast was used as a beacon by the fleet to assess the condition of the ionosphere throughout the HF band. Here is an example of the continuous loop transmitted by CFH when there was no shore-to-ship radio traffic. The letter "L" indicates the NATO area covered by CFH:

VVV VVV VVV CFH CFH CFH L L L     VVV VVV VVV CFH CFH CFH L L L ...

MORSE CODE AT 100 WORDS PER MINUTE !!!

As mentioned at the beginning, submarines below periscope depth could not copy the naval broadcast on a continuous basis so messages addressed to submarines were sent on special submarine schedules every 4 hours.

If the submarine was already at periscope depth or on the surface when the time came to copy the submarine schedule, it was normally dopied on the teletype broadcast because the equipment was already synchronized and ready to go. However, when time was of the essence and the submarine had to come up, copy the schedule and go back below, the schedule was copied on the morse code broadcast.

To minimize the time spent at periscope depth, the schedule on the morse code broadcast was sent at 100 words per minute !!!!  Everyone knows that morse code cannot be copied at that speed. Well, the morse code was not actually copied. It was recorded on a tape recorder to be copied later when the submarine was back below periscope depth.

Once the submarine had returned to the deep, the tape recorder was slowed down so morse code could be copied at 25 words per minute. Slowing down the tape recoder caused the sound pitch to go down so it was important to tune the signal to a high pitch when recording the schedule so copying would be easier.

Whenever it was time to send a submarine schedule on the naval broadcast, the Radioman at the shore station stopped the Wheatstone perforated tape which was sending traffic at 22 words per minute in morse code to the fleet. The speed of the Wheatstone perforated tape was then increased to send the submarine schedule in morse code at 100 words per minute.

The Radioman on the submarine used a tape recorder to record the submarine schedule. When the schedule was over, the shore station resumed the traffic to the fleet at 22 words per minute.

Classified messages received on morse code were coded into 5-letter groups. So once the messages coded in 5-letter groups had been typed on a typewriter, the task of decoding the messages began using the KL-7 crypto machine. This was quite a task if messages were long. The work was much easier on teletype which used in-line crypto. Once the messages had been copied on the teleprinter, all that was required is to rip off the message from the teleprinter, log it and deliver it to the Captain.

Each message sent to submarines had a serial number and each message was sent on four consecutive schedules. To make sure no messages were missed, a submarine had to copy at least every 4th schedule. In other words, the submarine had to go up to periscope depth at least every 16 hours. For operational reasons, this was not always possible. It was up to the Captain to decide if he should take the risk of missing the 4th consecutive schedule.

Missing four consecutive schedules was not a guarantee that messages had been missed. For example, if there were no new messages on the first two schedules that were missed, new messages that began on the third schedule would continue to be sent until the sixth schedule. This was in the Captain's mind as he decided if he should go up to periscope depth for the 4th schedule or wait for the next schedule.

Sometimes, messages were missed because the Captain, for operational reasons, had decided to miss a schedule which had messages being sent for the last time. At other times, the submarine had gone up to periscope depth at the last minute and ionospheric conditions had made it impossible to be ready on time for the schedule. For example, if a schedule started at 0400 GMT and the radio mast was raised at 0359 GMT there wasn't any time to retune the receiver to a better frequency if there was a lot of atmospheric noise (QRN) or fading (QSB). By the time a better frequency was found, the schedule had already started and could only be recorded in part only.

Whenever messages were missed, a service message had to be sent to the shore station via ship-to-shore requesting that the missed messages be sent again. When this happened, the missed messages were sent again on the next four consecutive schedules.

Those were the days....

Donald Courcy

18 June 2017

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