A schedule was an appointed time (i.e. every 4 hours) to come up to periscope depth (but not to the surface) to receive traffic on the naval broadcast frequency but not to transmit. CW and RATT (RTTY) naval broadcasts were transmitted simultaneously on 4, 6, 8, 12, 16/17, 22 and 25 MHz. There was also a CW broadcast on 115.3 kHz and a RATT broadcast on 73.6 kHz.
For CW schedules, the regular traffic running on the broadcast at 22 WPM would be stopped, and the submarine traffic was sent at 100 WPM. It was copied on a tape recorder at high speed and later on slowed down to 25 WPM to copy all the messages once the submarine returned to the deep. This minimizes the time that the submarine must spend at periscope depth.
For RATT schedules, submarine traffic replaced regular traffic at the allotted times. Each message addressed to a submarine had a serial number and was sent on 4 consecutive schedules. To make sure that a message was not missed, at least every 4th schedule had to be copied. But sometimes this was impossible due to operational requirements. The control room was kept informed on the number of schedules that were missed and the Captain decided whether to ascend for the next schedule. If the last 4 schedules were missed, that did not mean that the messages had been missed. If there were no new messages in the first schedule that were missed, then missing the 4th schedule was not a problem. New messages sent on the second missed schedule would still be sent on the fifth schedule.
Submarines did not send receipts. All messages sent from the shore station on four consecutive schedules were assumed to have been received. However, if a message was missed by a submarine for whatever reason, a request had to be sent by the submarine to transmit the missed message again. The message serial number was used as a reference. Upon receipt of the request, the shore station sent the message again on the next four consecutive schedules.
We did not need to come up ahead of a schedule on CW. As long as the Racal receiver was properly tuned and the tape recorder was ready, raising the radio mast only a few seconds before the start of the schedule was OK. The only adjustment to be made was the pitch of the receiver audio. High pitch was required because the pitch was lowered when the tape was replayed at 25 WPM on the tape recorder . If we were say at 500 feet, it would only takes us a minute or two to get up to periscope depth.
Transmitting was kept to a minimum during exercises or during special operations. Unless we were involved in a stealth spy mission, we had to send a check report every 72 hours to let Headquarters know that we were safe. The check report looked like this:
CHECK SEVEN TWO
The check report had an immediate precedence (O) and was sent on the calling frequency. Here is a typical call:
CFH3 CFH3 DE CGNQ CGNQ ZPP ZBO 1 O QRK CHF - 5 K
The '3' in CFH meant that the call is being made on 6 MHz. '2' was used for 4 MHz, '4' was used for 8 MHz, ' 5' was used for 12 MHz...etc...
ZPP means that it is a submarine surface message to be sent on the calling frequency. Otherwise we would shift to a working frequency.
ZBO 1 O means I have one immediate message. If I was requesting a missed message to be sent again, then the extra message would be indicated as ZBO 1 O 1 P. (P for Priority)
QRK CFH - 5 means that the navy broadcast is being copied on Morse code with a good quality signal. If I was copying teletype, I would say ZBZ CFH - 5 instead. This is important because it tells the shore station what to use to get back to me.
Normally, about 60 hours after the last check report had been sent (check+60), I would inform the control room (or the Captain) that we are at check+60. Thereafter, each time we came up to periscope depth, I would remind the control room how many hours left before the 72 hours expire. Depending on the exercise, the Captain would decide to go up right away for the check report or to wait until close to check+70. Waiting too long was a risky business because we relied entirely on the conditions of the ionosphere. What if the conditions were such that the check report had to be relayed via the Commonwealth or NATO networks, and therefore delayed. If a check report was not received at CANMARCOM before check +70, operation SUBMISS was triggered, meaning that a submarine might be missing. If the message was not received at check+72, operation SUBSUNK was triggered, meaning that there was a high probability that a submarine had sunk. This is the moment when all the NATO navies went on alert and began searching for the missing submarine.
Going back to the check report - , when I was informed that we were going up to send it, I had to be ready. Using ionospheric propagation predictions, I tuned the Racal-17 receiver for the best naval broadcast frequency for the time of the day (4, 6, 8, 12, etc... MHz). I also prepared the 618-T or the URC-32 transmitter on the calling frequency.
As soon as the radio mast went up and the bottom insulator cleared the surface, I loaded the HF antenna and called CFH on the calling frequency. As noted above, the shore station would know if I was monitoring CW (QRK) or teletype (ZBZ). CFH would stop their running tape of ongoing traffic on the CW or RATT broadcasts and would reply using a two-letter blank call sign:
CK CK de CFH CFH K
The running tape or ongoing traffic would not resume until all my messages had been received.
Upon hearing the reply to CK, I would assume it was for me and I would send my messages on the calling frequency. Each of my messages would be numbered. Let's say I sent the check report as # 1. Upon completing my first message, the receipt would come back on the broadcast frequency:
CK de CFH R 1 K
If I have more messages, I would continue sending on the calling frequency instead of shifting to a working frequency because the original message was a check report.
CFH would come back
CK de CFH R 2 K
After all traffic had been send, I would end my last message with AR. Let's say I had 3 messages.
CFH would come back
CK de CFH R 3 AR
CFH would resume their regular tapes or traffic. I would advise the control room that all traffic has been sent, the radio mast would be lowered and we would quickly return to the deep.
It became quite exciting when CFH could not be contacted when coming up for a check report. Other options would be to work CKN on the west coast, or a British shore station, such as Poldhu or Gibraltar, or as last priority, an American shore station.
Contributors and Credits:
1) Donald Courcy VE2GG <doncourcy(at)aol.com>
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