Ships Nostalgia banner

21 - 40 of 59 Posts

·
Registered
Joined
·
44 Posts
Does anyone remember how many four second dashes were required to set off an auto alarm?
Bob
ITU rules dictate he leaves a receiver tuned to 500 kc with a decoder attached - if that decoder hears at least four 4-second dashes each with 1-second seperation, relays in the decoder will clamp shut triggering alarm bells in the radio room, in the radio officer's sleeping quarters, and up on the bridge, to warn of a distress message about to be sent on 500 kc.
 

·
Registered
Joined
·
179 Posts
As noted four 4 second dashes would activate the A/A but the autokey would actually send twelve 4 second dashes with one second spacing followed by SOS (3 times ) followed by de and callsign (3 times). Then the actual distress message.If the AKD was not manually stopped it would go on for 36 hours of course without the distress message. A coast station could send it as well or another ship close by. Sometimes the A/A would go into alarm especially at night and it would be a coast station in Canada and you would be rounding the Cape.I think generally coast stations would take over the distress and co-ordinate the rescue. Silence periods would still be observed but the station involved would still send the twelve 4 second dashes and an updated distress message proceeded by SOS.Every message pertaining to the distress was proceeded by SOS and the recommended speed was 12 words per minute. I still practically fall out of my chair when i hear an SOS sent in some old movie, a bit like Pavlov's dog I suppose. Normal working was supposed to move to 512 kc/s but this was in theory because ships out of range of distress reception would go merrily calling until the QRT distress was sent in a very stern manner.
On occasion in a dead part of the world radio wise some one would check that the AKD was actually keying the emergency transmitter and not stop it until well past the 4th dash then realized that they were actually starting a distress call then it would abruptly stop followed by total silence, For all it's faults it was a very good system in the days before Satellite communication, I personally was not impressed with GMDSS and I generally found the person responsible for it, had very little knowledge or interest in it. When I left the radio room I never wanted anything more to do with GMDSS. On occasion when I was called to make it work it was usually operator error. Even as it was introduced I felt it was a poorly conceived concept. But that's my opinion.(to quote Mandy Rice Davis "he would say that")
While not a big fan of Marconi Marine equipment (especially their radars) I must pay complement to their a/a and akd being robust and reliable.
 

·
Registered
Joined
·
58 Posts
Does anyone remember how many four second dashes were required to set off an auto alarm?
Bob
I would guess that both were correct for different time periods, I'm guessing after 1959 when "Electronic Commuication" by Robert L. Shrader (W6BNB) was first published there was a change in the number of dashes, because even the 1991 6th edition says "three dashes" - it's obvious from comparing this with other publications and the bizarrely worded FCC regulations that Mr. Shrader (a dear friend of mine who died at his 99th year on April 11, 2012, who edited his book brilliantly never new about the change from 3 correct dashes to 4 correct dashe

From "MARINE RADIOTELEGRAPH OPERATOR LICENSE HANDBOOK" by Edward. M. Noll, 1975, 1st Edition, 1st Printing, copyright Howard W. Sams & Co., Inc.

From page 27:

The standard autoalarm signal involves the transmission of four-second pulses with intervening one-second spaces for a period of one minute. Thus twelve pulses are transmitted in a one-minute period. Autoalarm receivers must respond to four successive pulses of this type, setting off the alarm bells.

Ed Noll cites the FCC regulations in this book as being the edition of FCC Part 83 as of March 7. 1974.

§ 83.457 Tests of radiotelegraph auto alarm.
(a) The radio officer shall at least once every 24 when the ship is in open sea, outside of a harbor or port:

(1) Test the efficiency of the radiotelegraph auto alarm by using the testing device to determine if the apparatus will will respond to not less than 4 nor more then 12 consecutive dashes having the approximate duration of 4 seconds and the approximate spacing between dashes of 1 second, the timing to be made by reference to the seconds hand of the radiotelegraph station clock.

Noll, Edward M. “SHIPBOARD RADIOTELEGRAPH STATIONS AND OPERATOR LICENSING / AUTOALARM RECEIVER.” Marine Radiotelegraph Operator License Handbook, 1st ed., IBSN 0-672-21109-2 Chapter 1, p. 27., published by H.W. Sams, Indianapolis, IN, copyright 1975.

The identical wording is found in my October 1, 1987 Code of Federal Regulations, Chapter 47, Part 80 as:

§ 80.817 after Federal Communications Commission reorganized § 83 into a unified § 80 which was to have all the maritime regulations except for equipment specifications which were contained elsewhere in the FCC regulations, a copy of which I do not own, and the autoalarm specifications no longer are in that part as accessed by Internet.

However "Electronic Communication" by Robert L. Shrader, 6th Edition, Chapter 29-9 states that:

The radiotelegraph AA signal is 1 minute of alternate 4s on and 1s off A2A radio transmissions on 500 kHz.

The AA receiver times received dashes, accepting only those between 3.5 and 6 s long, if separated by 0.1 to 1.5 s spaces. After three such received dashes are accepted into memory the receiver relay closes, ringing bells and lighting lights in the radio station, on the bridge, and in the radio operator’s quarters.

Shrader, Robert L., “Chapter 26-9 MARITIME RADIO, Auto Alarms and Silent Periods.” In Electronic Communication, 6th ed., pp. 594–95, published by Glencoe, Macmillan-McGraw-Hill, Lake Forest, IL copyright 1991.

73
David J. Ring, Jr., N1EA
ex R/O USMM
 

·
Registered
Joined
·
18,765 Posts
As noted four 4 second dashes would activate the A/A but the autokey would actually send twelve 4 second dashes with one second spacing followed by SOS (3 times ) followed by de and callsign (3 times). Then the actual distress message.If the AKD was not manually stopped it would go on for 36 hours of course without the distress message. A coast station could send it as well or another ship close by......"
On later models, following the Distress Signal (SOS X3 de Callsign X3), the Autokey would send two 12 second dashes which were supposed to be for direction finding purposes.

John T
 

·
Premium Member
Joined
·
10,325 Posts
I am with the 4 dash brigade. I sailed with both the Seaguard and Lifeguard (on which I did my ticket).
 

·
Registered
Joined
·
44 Posts
I think the autokeyer sent 4 dashes, any 3 of which would activate the autoalarm. The 1960's Marconi autoalarm was an electromechanical wonder, whereas the AEI one, the Q29, was all valves and relays. The sequence had to be learnt off for the PMG exam. "S1 closes, energising SA....." and so on!
The system worked great especially in winter in the Med, when you'd frequently get woken up at night by distresses in the North Sea - quite unnecessarily re-broadcast by PCH, the very powerful Dutch station.
 

·
Registered
Joined
·
545 Posts
Did they ever invent an Auto Alarm that could hear the signal through night time static in the tropics ?
When I was visiting RAF Gan, they had an AA which if I remember correctly was just one continuous carcophy of static at night.
 

·
Registered
Joined
·
42 Posts
Sailed with the Type-M (Vigilant) auto alarm on several ships. It always managed to raise eyebrows on fellow crew members if they saw me setting it to work when I was going off watch. The vibrating reed had to be set in motion by means of giving a sharp blow to the side of the cabinet, while at the same time it was necessary to depress and spin the spring-loaded knob on the front panel (so as to engage its spindle with a gear on the motor shaft).....
I'm sorry you had to remind me of the "vibrating reed". On the good ship ss Appledore, in 1955, the alarm bell was just above my bed. The contact on the "reed" was burnt. I was rudely awakened on multiple occasions because the A-Alarm had been triggered. Invariably a false alarm. This was my first ship as sole R/O so I dutifully tried to keep the equipment going by burnishing the contacts to a bright sheen but, lo and behold, that only lasted a couple of days before I was struggling to do what was right, again. In the middle of the Pacific en route to Nahkodka near Valdivostok or wherever. Many moons away from a reed replacement. Can't remember what the final resolution was - but I longed to an undisturbed sleep and another ship.
 

·
Registered
Joined
·
701 Posts
As I mentioned above, my recollection from the PMG course and sailing with Marconi and other AAs in the early 60s, it was three dashes to set the bells ringing. The Marconi book Wireless At Sea The First Fifty Years mentions the development of and compulsory fitment of AAs from 1927 on but is silent on how many dashes were needed to set the device off.
in One Hundred Years of Maritime Radio by W D Goodwin he says: “the special receiver responded to three, four-second dashes spaced one second apart. After considerable testing the device was finally approved by the British Board of Trade in 1927.”
So, it looks like the question is not how many dashes but when did the regulations change?
It was all a long time ago for me and it doesn’t matter now in this modern GMDSS world.
Happy days
gwzm
 

·
Registered
Joined
·
193 Posts
Back in the 1950s a common PMG question required you to draw an auto alarm and describe how it registered an Alarm signal and actuated the alerting bells. Hatches, pawls and cams featured strongly.
At Riversdale we had an AEI AL90. (I think). In the orals, I was asked what relay did what on one of the dashes. I hadn’ t a clue.
When resitting the orals, I had learn’t everything about the AA.
The same examiner referred to his ‘case notes’. Said to me. “I think you will fully know the workings of the AL90 now”.
Then went on to ask me a question about another piece of gear!!
 

·
Registered
Joined
·
7 Posts
As noted four 4 second dashes would activate the A/A but the autokey would actually send twelve 4 second dashes with one second spacing followed by SOS (3 times ) followed by de and callsign (3 times). Then the actual distress message.If the AKD was not manually stopped it would go on for 36 hours of course without the distress message. A coast station could send it as well or another ship close by. Sometimes the A/A would go into alarm especially at night and it would be a coast station in Canada and you would be rounding the Cape.I think generally coast stations would take over the distress and co-ordinate the rescue. Silence periods would still be observed but the station involved would still send the twelve 4 second dashes and an updated distress message proceeded by SOS.Every message pertaining to the distress was proceeded by SOS and the recommended speed was 12 words per minute. I still practically fall out of my chair when i hear an SOS sent in some old movie, a bit like Pavlov's dog I suppose. Normal working was supposed to move to 512 kc/s but this was in theory because ships out of range of distress reception would go merrily calling until the QRT distress was sent in a very stern manner.
On occasion in a dead part of the world radio wise some one would check that the AKD was actually keying the emergency transmitter and not stop it until well past the 4th dash then realized that they were actually starting a distress call then it would abruptly stop followed by total silence, For all it's faults it was a very good system in the days before Satellite communication, I personally was not impressed with GMDSS and I generally found the person responsible for it, had very little knowledge or interest in it. When I left the radio room I never wanted anything more to do with GMDSS. On occasion when I was called to make it work it was usually operator error. Even as it was introduced I felt it was a poorly conceived concept. But that's my opinion.(to quote Mandy Rice Davis "he would say that")
While not a big fan of Marconi Marine equipment (especially their radars) I must pay complement to their a/a and akd being robust and reliable.
Yep, the correct auto alarm transmission was 12 four second dashes each separated by a one second space. However, A/A receiving equipment would actuate after receiving any four correct dashes and spaces. Back in the late 1970's I purchased a Marconi Seaguard auto alarm which is now residing in our garage. Information with the unit indicated that it had ben originally installed during the fitting our of the Commonwealth (of Australia) Lighthouse ship Cape Don/VLFQ. The Cape Don Society was contacted to see if they wanted it, but difficulties arose due to the ship is in Sydney and I live in Western Australia. Add in Covid-19 and so the A/A still resides in my garage.
 

·
Registered
Joined
·
179 Posts
Twelve 4 seconds and 1 second spacing I was referring to the akd. Of course the auto alarm worked on any four consecutive 4 second dashes and one second spacing should operate the auto alarm.
Another point is that the auto alarm would not reject a dashes and spaces that was not exactly correct, in case the operator on the vessel in distress was sending it by hand. In fact the radio room clock is segmented to facilitate this.
It is amazing that a Seaguard is in garage in Western Australia.
 

·
Premium Member
Joined
·
10,325 Posts
It would not be in my garage but whirring away in by lounge for all to appreciate. A clickety clickety clack AKD would be an ideal pairing.
 

·
Registered
Joined
·
6,089 Posts
Interesting comments using the AKD to test the Auto Alarm before going off watch.
Was keying the AA test oscillator with the AKD an eventual station requirement?
 

·
Registered
Joined
·
67 Posts
For the full info regarding the signal suggest you have look at the HMSO Hanbook for Radio Operators, this gives full detail regarding the signal, operations over 1 min & the A/A operating after 4 x 4 sec .dashes, with a spacing of 1 sec. between each dash (in case you have to send it by hand) and also that provided by AKD units should be capable of.
For Circuit if information, Daniallson & Mayo's "Marine Radio Manual" has a step buy step guide on the circuit of the all valve Lifeguard (it may also have the old camshaft version - sorry memory is not so good.
 

Attachments

·
Registered
Joined
·
545 Posts
A B E H D C S
I won't regale you with the (rude) mnemonic I made up to remember them for my exam in 1965
 

·
Registered
Joined
·
67 Posts
It was also in my Part 2, however, after trying time and time again to understand how this infernal AA worked, would believe me if I admitted it clicked on the evening prior to exam day, and low and behold, there was a question on it in the exam paper, and I actually picked to answer it, and I passed !
 

·
Registered
Joined
·
19 Posts
I sailed in the late 60s early 70s. I sailed mainly with Seaguards and Lifeguards, but I seem to remember sailing with an older piece of kit that only needed three dashes. I think it was a Marconi Vigilant.
 

·
Registered
Joined
·
107 Posts
I still have my PMG note book from the late fifties which contains a circuit diagram and my written notes on the workings of the selector mechanism of the AA. They state quite clearly that the alarm will be activated and the bells ring on receiving three four second dashes subject to them adhering to the constraints imposed by the makers. i.e. the period between each dash and of course the length of the dash. The PMG exam that year required one to draw and explain the operation of the mechanism. Yippee I passed the exam and promptly put away my notes for the next 61 years.
 
21 - 40 of 59 Posts
Top