Re: A Real SOS (OT)

[Mike Morrow-3]

Ron wrote:

> By 1980 receivers had grown very selective, but the fact was that a great
> many ships still used a regenerative receiver as the "backup" in case the
> main receiver was out of commission for some reason.

The auto-alarm (AA) receivers were also designed to be broad enough to detect
A2 (MCW) distress AA signals from 492 to 508 kHz.  Typically the AA receiver
was a dedicated unit of TRF design feeding simple electronics capable of
detecting the distress auto-alarm signal of twelve four-second dashes with
one-second spacing sent in one minute's time.

The AA signal is one of the most interesting portions of the distress signal
in the link to the Morse traffic containing the M/V Prinsendam/PJTA SOS.  I
recommend the web page ( http://www.qsl.net/n1ea/ )of N1EA, the assistant
radio officer on the US merchant ship ship Williamsburg/WGOA that came to
the rescue from 120 nm away after hearing the SOS DE PJTA signal.

More details and background are provided, along with direct link to an MP3
version on the SOS traffic by clicking the SOS DE PJTA button on that page.
Apparently, the decision to send the SOS was made by the Prinsendam's chief
radio officer, Jack van der Zee, and not the ship's master.  Very unusual!

Also, the QRZ.COM page for the chief radio officer on the Williamsburg has
a lot of interesting related information:  http://www.qrz.com/db/ns1l

Both radio officers of the Williamsburg are hams (NS1L, N1EA).

> Some of the signals in the link below sound like they have modulation. They
> do. MCW was the norm for emergency traffic so they could be copied even on a
> receiver without a BFO.

Even the emergency lifeboat transmitters like the SCR-578 and AN/CRT-3 and
commercial equivalents, plus all the larger lifeboat emergency receiver and
transmitters like the RCMA ET-8053 (AN/SRC-6) and the Mackay 401-A (AN/SRC-6A)
sent MCW on 500 kHz.  That actually complicated their design and increased
the power consumption (generated by a human on a hand-crank), compared to a
simple A1 transmitter.  (I collect these sets.)

> The possibility of an SOS not being heard at all in the bedlam is what
> launched the twice-hourly "silent periods" when all ships fell silent and
> the R.O.s listened on 500 kHz for three minutes.

Yep, from minute 15 to 18 and 45 to 48 each hour.  Any Morse traffic being sent
on ANY maritime frequency MF or HF would be paused with a "AS SP" when minute
15 and 45 came up on the clock so that ROs on any frequency could turn their
attention to 500 kHz.

The old MF 405 to 535 kHz Maritime Morse band was an amazing place at night.
For years I kept a bedside receiver tuned to 500 kHz.

> This link is a real SOS recorded in 1980 when the MV Prinsendam had an
> engine room fire and a flooded engine room. It begins with a series of long
> dashes. That was the standard opening that was supposed to set off automatic
> alarm bells on any vessels whose radio rooms were not operating at that
> moment. The bells went off on the navigating bridge and right over the bed
> were Sparks would be sleeping. Following the dashes the SOS and emergency
> message begins.
>
> http://mikea.ath.cx/www.n1ea.coastalradio.org.uk/EJM_CD3_Track03_SOS_de_PJTA.zip

It has always been interesting to me that the radio officer on the Prinsendam,
technically did *not* send the SOS correctly.  It's supposed to be sent as as
one very distinctive signal of ...---..., yet PJTA sent ... --- ... with
definite space between the S, the O, and the S.  But in reality, it's those
four-second dashes of the AA signal that draw the most attention!

Technology did not move very fast in the communications of the merchant marine.
When I took my Second Class Radiotelegraph exam in 1981, the exam material was
dated 1961 and required schematic drawing and short answers in addition to
multiple choice.  I never felt the elation of passing any other FCC exam
that I got after passing the commercial radiotelegraph exam.  Merchant marine
MF Morse signals were, IMHO, the most interesting signals found on the air.  In
high school in the mid-1960s I used a military surplus BC-453-B command set
receiver to copy those signals.

I'll be very interested in the KX3's capabilities on the new MF band, even though
the maritime signals are long gone.

73,
Mike / KK5F
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[w5tvw]

Mike,

Interesting!  I didn 't know you collected lifeboat radios!  One of the
neatest ones I remember was the little Marconi one whose name I cannot
recall now.  It came after the big heavy clumsy one they had named the
"Salvita"  or "Salvor" .  My memory of it is too fuzzy now, too many years
ago!  Anyway it was in a rectangular case about same height and width of a
shoebox but about two and a half times longer!  I did 8364 and 500 khz
CW/MCW
and A3 voice on 2182.  There was a Swedish set that was very nice for it's
size,I think made by STC.  It had a receiver for 8 mhz that tuned a limited
band for CW and lots of tankers had two of them.  One in the lifeboat and
one in the forecastle of the ship.  Several ships I did inspections on had
an emergency antenna erected for that set, so it could be used to
communicate during emergencies, if the tanker broke into two parts (which
happened several times I gather) and left people stranded on the floating
bow of the ship!  It was reassuring when I did an inspection and actually
called WNU Slidell on 500 khz and raised him for the test.  It was easy
enough to crank and work the key single handed.  With the old RCA and Mackay
sets it took 2 people to operate one of those, one cranking one operating.

If they were still in use, I'd imagine one could build a tiny radio now
capable of more than the old tube stuff that used to be around then.  Mackay
built a solid state lifeboat set, but it was an awkward thing to use and
could have been much smaller and lighter for what it was.

73

Sandy W5TVW
-----Original Message-----
From: Mike Morrow
Sent: Saturday, April 14, 2012 5:56 AM
To: [hidden email]
Subject: Re: [Elecraft] A Real SOS (OT)

Ron wrote:

> By 1980 receivers had grown very selective, but the fact was that a great
> many ships still used a regenerative receiver as the "backup" in case the
> main receiver was out of commission for some reason.

The auto-alarm (AA) receivers were also designed to be broad enough to
detect
A2 (MCW) distress AA signals from 492 to 508 kHz.  Typically the AA receiver
was a dedicated unit of TRF design feeding simple electronics capable of
detecting the distress auto-alarm signal of twelve four-second dashes with
one-second spacing sent in one minute's time.

The AA signal is one of the most interesting portions of the distress signal
in the link to the Morse traffic containing the M/V Prinsendam/PJTA SOS.  I
recommend the web page ( http://www.qsl.net/n1ea/ )of N1EA, the assistant
radio officer on the US merchant ship ship Williamsburg/WGOA that came to
the rescue from 120 nm away after hearing the SOS DE PJTA signal.

More details and background are provided, along with direct link to an MP3
version on the SOS traffic by clicking the SOS DE PJTA button on that page.
Apparently, the decision to send the SOS was made by the Prinsendam's chief
radio officer, Jack van der Zee, and not the ship's master.  Very unusual!

Also, the QRZ.COM page for the chief radio officer on the Williamsburg has
a lot of interesting related information:  http://www.qrz.com/db/ns1l

Both radio officers of the Williamsburg are hams (NS1L, N1EA).

> Some of the signals in the link below sound like they have modulation.
> They
> do. MCW was the norm for emergency traffic so they could be copied even on
> a
> receiver without a BFO.

Even the emergency lifeboat transmitters like the SCR-578 and AN/CRT-3 and
commercial equivalents, plus all the larger lifeboat emergency receiver and
transmitters like the RCMA ET-8053 (AN/SRC-6) and the Mackay 401-A
(AN/SRC-6A)
sent MCW on 500 kHz.  That actually complicated their design and increased
the power consumption (generated by a human on a hand-crank), compared to a
simple A1 transmitter.  (I collect these sets.)

> The possibility of an SOS not being heard at all in the bedlam is what
> launched the twice-hourly "silent periods" when all ships fell silent and
> the R.O.s listened on 500 kHz for three minutes.

Yep, from minute 15 to 18 and 45 to 48 each hour.  Any Morse traffic being
sent
on ANY maritime frequency MF or HF would be paused with a "AS SP" when
minute
15 and 45 came up on the clock so that ROs on any frequency could turn their
attention to 500 kHz.

The old MF 405 to 535 kHz Maritime Morse band was an amazing place at night.
For years I kept a bedside receiver tuned to 500 kHz.

> This link is a real SOS recorded in 1980 when the MV Prinsendam had an
> engine room fire and a flooded engine room. It begins with a series of
> long
> dashes. That was the standard opening that was supposed to set off
> automatic
> alarm bells on any vessels whose radio rooms were not operating at that
> moment. The bells went off on the navigating bridge and right over the bed
> were Sparks would be sleeping. Following the dashes the SOS and emergency
> message begins.
>
> http://mikea.ath.cx/www.n1ea.coastalradio.org.uk/EJM_CD3_Track03_SOS_de_PJTA.zip

It has always been interesting to me that the radio officer on the
Prinsendam,
technically did *not* send the SOS correctly.  It's supposed to be sent as
as
one very distinctive signal of ...---..., yet PJTA sent ... --- ... with
definite space between the S, the O, and the S.  But in reality, it's those
four-second dashes of the AA signal that draw the most attention!

Technology did not move very fast in the communications of the merchant
marine.
When I took my Second Class Radiotelegraph exam in 1981, the exam material
was
dated 1961 and required schematic drawing and short answers in addition to
multiple choice.  I never felt the elation of passing any other FCC exam
that I got after passing the commercial radiotelegraph exam.  Merchant
marine
MF Morse signals were, IMHO, the most interesting signals found on the air.
In
high school in the mid-1960s I used a military surplus BC-453-B command set
receiver to copy those signals.

I'll be very interested in the KX3's capabilities on the new MF band, even
though
the maritime signals are long gone.

73,
Mike / KK5F
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
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Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html