Moderated Discussion Areas
ContinuousWave: Small Boat Electrical
|Author||Topic: MAYDAY Call|
posted 12-27-2007 02:13 AM ET (US)
I found this audio recording of an actual MAYDAY situation to be noteworthy with regard to the quality of the radio transmission from the vessel in distress. I noted that there is some spurious whine or noise on the modulation from the vessel in distress. Also, the operator of the vessel sounds like he is shouting into the microphone of his transmitter, causing his audio to be distorted. Later in the recording the operator of the vessel in distress appears to lower his voice a bit and his radio transmission becomes much more intelligible. There also appears to be a lot wind blasts into the microphone, either due to wind or poor microphone technique.
Listen and see how difficult it is to copy the distress call due to the distortion and spurious noise on the transmission.
posted 12-28-2007 02:53 PM ET (US)
I had been thinking that the VHF transmitters which reported position were a bit of electronic overkill. Maybe I'll rethink that Dave
posted 12-28-2007 04:22 PM ET (US)
Ah ..... remember the six P's.
Prior Planning Prevent Piss Poor Performance!
Know what your going to say before you have to say it.
posted 12-28-2007 06:38 PM ET (US)
The person making the distress call was holding the microphone too close, shouting and talking too fast. The hum in the background is just icing on the cake. The replies from the Coast Guard station leave a lot to be desired, too. His transmissions were technically better, but he talked way, way too fast. If he wasn't reprimanded, he should have been.
posted 12-29-2007 02:14 PM ET (US)
On closer listening, I think the strong hum might be in the recording system, not in the actual transmissions. Listening with headphones and playing the recording several times, I compiled this partial transcript:
posted 12-29-2007 04:38 PM ET (US)
VHF sometimes makes cell phones sound good.
The recording is a .WAV file. I think that's 8-bit, which
The real message here is: when stuff happens, keep your head
posted 12-29-2007 07:09 PM ET (US)
I have also noticed over the years that for whatever reason, some people are much better deciphering radio chatter then others.
I am one of the handicap when it comes to making sense of some of the unintelligible VHF garble, and the person next to me might say they understood.
I grew up listening to SSB on my Allied ham radio, so I would think I would have an advantage, but no!
I live close to Newark International Airport and the pilots seem to be experts at mumbling as the tower clearly understands and replies back in a very clear transmissions.
posted 12-29-2007 08:18 PM ET (US)
From the recording, it seems as though the Coast Guard was able to copy the location of the vessel when it was given (in the first transmission). I make this assumption because the Coast Guard never asks for a repeat, and they say there is a vessel en route.
It is also entirely possible that the distortion heard in the transmissions from the vessel occurred more in the recording process than in the actual transmissions.
The monophonic digital audio file is encoded with 16-bit encoding and with an 11-kHz sample rate. Those parameters are usually adequate for voice reproduction with good communication quality.
I also think the radio watchstander at the Coast Guard spoke rather rapidly. You can hear a sense of excitement in his voice.
I also assume that this transmission was made on Channel 16. It is important to remember that a distress call should be made on Channel 16, which is reserved for this purpose. It is also important to remember that all vessels which are equipped with a marine radio should maintain a watch on Channel 16. This is nicely explained in
Radio Watchkeeping Regulations
posted 12-30-2007 12:48 AM ET (US)
Not "should maintain a watch on 16", but rather "MUST maintain
a watch on 16". If you have a VHF radio, you must monitor
16 if you aren't using it on another channel.
posted 12-30-2007 01:37 PM ET (US)
I think it's a bad assumption that the Coast Guard heard the distressed vessel's location given in the first transmission of the recording. If that had been the case, I doubt they would announce, "we have a vessel en-route at this time" so quickly, and without asking for confirmation of the location. It could be that they learned of the situation previous to the vessel's Mayday call.
Regarding the hum in the background of the boat's transmissions, I believe it came from the boat, not from the recording system. In my experience, such recordings are made at the base station responsible for dispatching an emergency response. The base station operator's voice is captured on its way to the transmitter, while the remote radio user's audio is taken from the base station's radio receiver. Unless there is a serious defect in the equipment, the recording should reflect what the base station operator heard.
posted 01-07-2008 09:06 AM ET (US)
The Coast Guard's new radio system, RESCUE 21, was first deployed at Chincoteague in the Spring of 2006. The system includes a built-in digital voice recorder system. Based on that information, I have a feeling that the recording we've been listening to was made with RESCUE 21 equipment.
See: http://www.nationaldefensemagazine.org/issues/2006/may/U.S.CoastGuard. htm for more information about RESCUE 21 and some of the problem encountered in its deployment.
posted 01-07-2008 06:50 PM ET (US)
Despite his excitement and tendency to yell into the microphone in what was likely a very traumatic experience, do you think that this boater could have hit his "DSC-Distress" button on his DSC-Enabled VHF? That would have given the USCG an exact location to dispatch a rescue boat or helicopter.
This is interesting information, and it reminds me first and foremost why I like my Whaler, but also to be sure to speak clearly and enunciate my words when calling for help!
I also agree that the Coastie on the recording was talking very fast - if I were trying to plug a hole in my sinking boat, I'm not sure I would have understood his questions or instructions - at least, not enough to calm me down. The whole purpose of speaking in a metered calm tone in these situations is to help the hyper-alert person facing an emergency to calm down and understand/receive instructions on what to do.
Considering that his passenger had donned a PFD and swam for shore, either the situation aboard was dire indeed, or the atmosphere aboard was in a high-state of panic.
Incidentally, if you are close enough to shore for your passenger to reasonably "make a swim for it", aren't you close enough that you should be able to run the boat aground and save it from sinking?
posted 01-14-2008 04:56 AM ET (US)
I downloaded the [audio recording of the MAYDAY call],whatever that is worth. I monitor 13/16 daily via external speaker upgrades. [Because of the combination of] of speaker, good antenna, [good] vhf unit, many years of listening, [and many years of] assisting others trouble shoot, I can tell if another transmission is distant, low battery, bad antenna, bad or cheap microphone, etc. I would not classify this as a bad recording of the MAYDAY call because the USCG is pretty clear. On a scale of 1-10, I would give the [recording] itself a 6 rating.
The distress radio is simply distant, bad mic or small antenna, or all of the above.
Sometimes I wonder who needs to be trained in emergency radio proceedures, Citizens or USCG? I suppose, just like 911, some operators are better than others.
DSCs are great. [RESCUE 21] is scheduled to be adapted to the NW area this summer.
posted 01-15-2008 03:20 PM ET (US)
Wikipedia had a link to a nice distress card procedure. I liked it so much I posted it next to the radio...
posted 01-15-2008 03:54 PM ET (US)
ICOM provide two stickers when you purchase a VHF. You can place these stickers around your vhf or if you prefer you can lamimate them for use as needed. My navy training included distress voice calls we memorized what was to transmitted and practiced it until it became second nature.
I also carry a white & black china marker (grease pencil) that are located by my radio in case I have to copy a position, call sign etc. You can write on your windshield or helm area. The grease comes right off.
Here's what they look like.
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