Reports from NMO - 500kc Procedures
Copyright © 1994 by Jeffrey Herman All rights reserved.
The first thing an op coming on watch does is to check his clock against WWV (ITU regs!), for certain actions on 500 have to be timed down to the second. In the log it goes:
OBTAINED WWVH TIME TICK - CLOCK CORRECT 2500KC 0900Z
Because of the steady stream of signals on 500 a weak station sending a distress message might not be heard. And at one time, calls AND traffic were passed on 500 - there was no shifting to working frequencies to pass messages. Thus silent periods were created.
These consist of two three-minute intervals, in which worldwide no one transmits - volume controls are turned up - ears are pressed to the speaker grill - one's breath is held, from minute :15 to minute :18, and again from minute :45 to minute :48. Even traffic being passed on working frequencies would stop. For example, if I were sending the WX on 440kc:
"...HIGH PRESSURE 1028MB 35.8N 132.3W BT CQ CQ CQ DE NMO AS SP QSY 500 AR"
at which point myself and my listening audience would shift back up to 500 for that particular 3 minutes. Woe to the station whose clock is off or who forgets the SP, for a half dozen stations might jump on him:
VLA VLA VLA DE 3FWR 3FWR K QRT SP SP SRI SP OK SRI SP SP
(the ship 3FWR calls the shore station VLA - someone breaks in to tell him to stop transmitting; he responds with `sorry' and is still scolded, says he's sorry a second time, and is scolded again), although someone somewhere in the Pacific was more direct and to the point:
JNKB JNKB DE FHWN FHWN SHUT UP SP (at 30 wpm)
Now, the last 15 seconds of a Silent Period was set aside for safety and urgent preliminary transmissions ("prelims"): Broadcasts From the lowest to the highest priority, the following types of broadcasts exist:
CQ - meaning ``Hello All Ships and Stations'' sent in a 3X3 format:
CQ CQ CQ DE FUM FUM FUM WX AND TFC LIST QSW 430 AR
Here, the shore station FUM, French Navy Tahiti, makes an announcement that he'll be sending the weather and his traffic list on 430 kc. The CQ is the most common broadcast announcement; one will go out every few minutes from someone somewhere.
TTT - this is the prosign for a safety broadcast: storm warnings, navigation hazards, or anything involving the safety of shipping:
TTT TTT TTT CQ DE ZLW ZLW ZLW CYCLONE WARNING NR 38 QSW 475 UP
Each T is longer than usually sent to provide a very distinctive sound. During the last 15 seconds of a silent period a half dozen TTT's would be going out. In particular, the shore stations running around the perimeter of Australia would sent the same TTT, one station following the previous station. Everyone in the Pacific wanted to be the first one out with their TTT announcement instead of waiting for a station 1000 miles away to finish, so many time they'd all go out at once. What a mess!
XXX - this prosign is indicative of an urgent broadcast where shipping and lives might be in danger (the CO might order the auto alarm sent prior to the preliminary announcement on 500):
XXX XXX XXX CQ DE NMO NMO NMO HURRICANE WARNING QSW 440 AR
Again, each X is drawn out so as to provide a very distinctive sound. This, as with the TTT announcements, went out during the last 15 seconds of a silent period. Those sending a TTT were supposed to give way to an XXX (remember, everyone is working duplex or full QSK - you MUST be able to hear anyone sending under you).
SOS - the darkest hour of an ops career is when the Captain of the ship enters the radio shack, hands the op a piece of paper, and says ``Send the SOS - here's our position''. International procedures dictate *every* step the operator will take:
- Auto Alarm (AA): twelve 4-second dashes, each dash followed by a one-second pause, sent in A2 (modulated CW). ITU regs demand that every ship carry an AA decoding receiver; this decoder will ONLY respond to AA's sent in A2. In A2 the transmitter is modulated by a tone (two meter repeaters ID in this manner). Thus, what you would hear on your receiver, with your BFO on would be several tones, or harmonics - very musical and an attention getter; a station sending CW in A2 sounds like someone sending code on a piano keyboard by pressing a half dozen keys at once! [One very old book in my collection describes an easy (but archaic) method of modulating a CW transmitter: a toothed wheel is rotated at several hundred RPM with a wiper, connected to the keying circuit of the xmtr, rubbing over the teeth of the wheel. Crude but effective.]
- The op in distress now must wait two minutes (if possible - if his feet are getting wet then he skips this step) for off duty ops, on board other ships that have received his AA, to get to their radio rooms. 500 kc is now in a continuous silent period until the controlling station sends:
- The distress broadcast. All traffic pertaining to the distress will be sent on 500. Those not in a position to assist will move to 512 kc, the alternate calling freq when 500 is in distress use. Here is a typical distress bcst (sent at no more than 16 wpm (ITU regs!)):
The AA will activate the decoder onboard every ship within receiving distance after just four correctly sent dashes are received; the decoders are designed to be a bit forgiving regarding the timing of the AA dash: they will accept, as a valid dash, a dash of between 3.5s and 6s in length (just in case the sending op is nervous!). As mentioned, only four correct dashes are needed, but just to be sure, ITU demands that twelve be sent. Once the AA decoder receives four dashes its latching relay closes activating lights and bells in the radio room, the radio officer's stateroom, and up on the bridge.
CQ CQ CQ DE (cs of controlling stn) QUM 500 KC VA Note that QUM
Meaning distress traffic has ended - resume normal traffic. The controlling station is the distressed vessel - he can and does give control to the first responding shore station; thus if I was the first shore stn to respond, then NMO would be the controlling stn. Woe to ANY ship or shore station who transmits normal tfc during a distress:
9JBV 9JBV DE HCKO HCKO HW OM K QRT QRT QRT SOS 500 (sent by dozens of stations)
SOS SOS SOS CQ DE 5TER 5TER 5TER BT SOS 281751Z MV PANAMA TRADER TAKING ON WATER ENGINE ROOM FLOODED POSN 13.73N 152.55W 13.73N 152.55W NEED IMMEDIATE ASSISTANCE AR MASTER SOS
This broadcast would be followed by a 10 second long dash to aid receiving stations in getting a bearing to 5TER's position. Then would come the acknowledgements:
SOS 5TER 5TER DE NMO NMO NMO R R R
SOS SOS 5TER DE KFS KFS KFS R R R
SOS SOS 5TER 5TER 5TER DE JNA JNA JNA R R R
SOS SOS 5TER 5TER 5TER DE WNPH WNPH WNPH R R R SOS WE ARE IN POSN 11.81N 151.32W CHANGING CSE TO UR POSN WILL GET ETA K SOS
WNPH DE 5TER R TU HERE IS MORE INFO .....
The first thing you'll notice is that ALL transmissions MUST start with SOS (ITU regs!). What happened here is that three shore stns QSL'd the distress bcst - ITU regs state that you must send R R R SOS; a nearby ship also QSL'd and is proceeding to 5TER's posn.
The 500 op at NMO (me!) would be on the phone to RCC (Rescue Coordination Center) passing all info - RCC would launch aircraft and also key up the AMVER computer to check for nearby vessels. Suppose the AMVER computer shows that KPLH is steaming nearby:
SOS KPLH KPLH KPLH DE NMO NMO NMO
would be sent every 5 minutes both on 500kc and on all the HF freqs.
In case no ship responded to 5TER's distress call, 5TER might give control to NMO. We would then periodically send:
DDD SOS SOS SOS DDD CQ DE NMO NMO NMO BT
where the DDD indicates that NMO is relaying a distress.
Other Broadcasts I had mentioned that the last 15 seconds of the silent period were reserved for safety (TTT) and urgent (XXX) preliminary broadcasts. The problem was that 10 or 20 shore stations might have such a broadcast to put out and none of them knew who else would be a sending one - the result was sometimes a mess. To hear a dozen shore stations trying to send at once:
TTT TTT TTT CQ DE ...
was extremely funny! Thus, some would start a bit earlier than H:17:45 or H:47:45. I would start hearing
TTT TTT TTT CQ DE ...
sometimes as early as the last 30 seconds of an SP.
Now, EVERY shore station worked duplex and everyone wanted to be the first to get their broadcast out. The Japanese stations were always the most polite. I'd hear a New Zealand TTT and an Australia TTT and a Japanese TTT and the Japanese station would always stop his bcst to yield to the others. Once the freq was quiet then the Japanese station would start his TTT prelim again.
Oh, a prelim broadcast is the short announcement on 500 telling everyone to shift to one's working freq for the full bcst text:
XXX XXX XXX CQ DE VLA VLA VLA URGENT MARINE BCST MAN OVERBOARD QSW 472 UP
is a prelim bcst. The Australian shore stations were a well-behaved unit (even though they might crush other countries trying to send prelims!). The following Aussie stations would take turns sending their prelims - as soon as one finished the next would start: VII, VIA, VIR, VID, VIS, VIT, VIM, VIB. The only New Zealand shore station I used to hear was: ZLZ.
Other South Pacific shore stations I heard nightly were: FJP - New Calidonia 3DP - Fiji Islands P2M - Papua New Guinea DUQ - Samoa 8BB - Indonesia VJZ - New Britain FUM - Tahiti (French Navy) XSU - can't remember - used to hear a lot of X__ shore stations, and ones from Korea, Philippines, China, Central and South America... North Pacific West Coast shore station that would boom in nightly included: NMQ - USCG Radio Long Beach CA NMC - USCG Radio San Francisco CA NOJ - USCG Radio Alaska KFS - San Fran commercial station KPH - another SF commercial station KHK - Honolulu commercial station KOK - Southern California commercial station.
To hams, 500 would have been a DX'ers dream but we took the excellent conditions for granted. Keep in mind that NMO had a *very* long a *very* long longwire receiving antenna (over one mile in length). Not only would there be pile ups at the end of a silent period, but also, at the top of each hour; that's when the low priority ``CQ CQ CQ DE ... WX AND TFC LIST QSW ... AR'' type of prelims would go out.
So, not wanting to take a number and wait for others, prior to sending a prelim bcst I would always send: dit dit dit (or I E) (i.e. .. . ) as a way of saying ``Hey - don't anyone else send anything because I'm running 10 thousand Watts and in A2 and I'll crush you...'' or something like that.
Seriously, if I had a safety or urgent to send at the end of an SP, as I was sending my TTT or XXX I'd hear other countries under me as they started their prelim and they would suddenly stop when they heard us; NMO must have put out a commanding signal to the entire Pacific for everyone to yield to us.
Generally, 500 was very orderly and eveyone was a gentleman.
Frequency scheme: Ships had a choice of using any of the following working frequencies: 425, 454, 468, 480, and 512 kc. Shore stations only had one fixed working freq, so during an initial call on 500 a shore station would give his working freq and the ship would choose one of the above to get as close as possible (so as to work duplex):
3LF 3LF 3LF DE CKHB CKHB TR K CKHB DE 3LF GE QSW 471 K DE CKHB R 471/480 UP R UP EE EE
Here, the ship CKHB called the shore stn 3LF wanting to pass a travel report (TR); 3LF has a fixed working freq of 471 so the ship chose to use 480: 471/480 means ``you use 471 and I'll use 480''. Why these particular choice of frequencies? Note that 454 kc was the old 660 meter wavelength, 480 kc = 625 meters, and of course, our star frequency 500 kc = 600 meters.
Oh, if you haven't guessed, shore stations have 3 character callsigns, and ships have 4 character calls. Many folks have shown their suprise that this kind of activity was occuring, on a worldwide scale, just below the broadcast band. But as a young pup I knew something was lurking just below the rock and roll band; living near NMQ (USCG Radio Long Beach, CA) I would ocassionally hear an unusual on-and-off hissing sound which would get stronger the lower I tuned: sheeeesh shesh sheeeesh shesh sheeeesh sheeeesh shesh sheeeesh (NMQ sending their CQ - of course my AM table top tube radio didn't have a BFO). That prompted me to both study the code and take the cover off my AM radio to move to `down' to the source of this noise (boy did I ever ruin that radio; thank goodness my parents bought me a Heathkit shortwave receiver - with a BFO).