With all the programs on TV this last week or so about the Titanic, I happened to catch a bit of one that started with the distress message from Titanic.
The purported message was in Morse and was a series of 'hissing' pulses on a quite background.
On reflection, I realized that I have no idea what code reception would have sounded like on the Marconi system in April of 1912. Firstly, the detector was, I believe, either a coherier or the Marconi metal tape unit, although on the other ships it may have been a 'crystal' detector. In any case I doubt that you would hear the hiss of the arc of the transmitter, but I don't know what you would hear in the earphones from those various detectors. Also, with the relatively broadband receivers, I would assume the 'atmospherics' would have been substantial, but again, no idea what that would sound like.
Lastly, I seem to recall that in the early days, the code used was not Morse but a special Marconi code.
Anyone on this NG know what reception would have really sounded like on April 15, 1912??
"nesesu" <neil_sutcli...@telus.net> wrote in message
news:11744688.363.1334517720064.JavaMail.geo-discussion-forums@pbbph3...
With all the programs on TV this last week or so about the Titanic, I happened to catch a bit of one that started with the distress message from Titanic.
The purported message was in Morse and was a series of 'hissing' pulses on a quite background.
On reflection, I realized that I have no idea what code reception would have sounded like on the Marconi system in April of 1912. Firstly, the detector was, I believe, either a coherier or the Marconi metal tape unit, although on the other ships it may have been a 'crystal' detector. In any case I doubt that you would hear the hiss of the arc of the transmitter, but I don't know what you would hear in the earphones from those various detectors. Also, with the relatively broadband receivers, I would assume the 'atmospherics' would have been substantial, but again, no idea what that would sound like.
Lastly, I seem to recall that in the early days, the code used was not Morse but a special Marconi code.
yea
Anyone on this NG know what reception would have really sounded like on April 15, 1912??
Neil S.
====================
Response:
++
They used spark gap transmitters. They sounded like buzz. One of the traveling Titantic exibits years ago had a tape recording of exactly what a spark gap transmitter sounded like....like fast buzz really, rather low in pitch, quite unlike the sounds generated by a BFO. Not hard to listen to at all. They did transmit SOS, which was new at the time, as well as the old distress symbol, which I have forgotten for the moment. And I just threw out my QST, which had an article on that subject two months ago. I don't seem to be able to activate QST on line this PM.
"nesesu" <neil_sutcli...@telus.net> wrote in message
news:11744688.363.1334517720064.JavaMail.geo-discussion-forums@pbbph3...
With all the programs on TV this last week or so about the Titanic, I happened to catch a bit of one that started with the distress message from Titanic.
The purported message was in Morse and was a series of 'hissing' pulses on a quite background.
On reflection, I realized that I have no idea what code reception would have sounded like on the Marconi system in April of 1912. Firstly, the detector was, I believe, either a coherier or the Marconi metal tape unit, although on the other ships it may have been a 'crystal' detector. In any case I doubt that you would hear the hiss of the arc of the transmitter, but I don't know what you would hear in the earphones from those various detectors. Also, with the relatively broadband receivers, I would assume the 'atmospherics' would have been substantial, but again, no idea what that would sound like.
Lastly, I seem to recall that in the early days, the code used was not Morse but a special Marconi code.
Anyone on this NG know what reception would have really sounded like on April 15, 1912??
Neil S.
==============
Here is a BBC clip. I looked it up through QST.
Wireless operators originally used Marconi's "CQD" distress signal. "CQ" was the signal to stop transmission and pay attention. The "D" was added to signal distress. In 1906 the International Radio Telegraphic Convention in Berlin created the signal "SOS" for summoning assistance. The letters were chosen for their simplicity in Morse Code - three dots, three dashes and three dots. While the "SOS" superseded "CQD" in 1908 Marconi operators rarely used it. It became standard after the sinking of the Titanic.
"nesesu" <neil_sutcli...@telus.net> wrote in message
news:11744688.363.1334517720064.JavaMail.geo-discussion-forums@pbbph3...
With all the programs on TV this last week or so about the Titanic, I happened to catch a bit of one that started with the distress message from Titanic.
The purported message was in Morse and was a series of 'hissing' pulses on a quite background.
On reflection, I realized that I have no idea what code reception would have sounded like on the Marconi system in April of 1912. Firstly, the detector was, I believe, either a coherier or the Marconi metal tape unit, although on the other ships it may have been a 'crystal' detector. In any case I doubt that you would hear the hiss of the arc of the transmitter, but I don't know what you would hear in the earphones from those various detectors. Also, with the relatively broadband receivers, I would assume the 'atmospherics' would have been substantial, but again, no idea what that would sound like.
Lastly, I seem to recall that in the early days, the code used was not Morse but a special Marconi code.
Anyone on this NG know what reception would have really sounded like on April 15, 1912??
Neil S.
===============
Here is a link to the last hour or so of the Titanic, with a simulation of the signals and then translated into words.
"nesesu" <neil_sutcli...@telus.net> wrote in message
news:11744688.363.1334517720064.JavaMail.geo-discussion-forums@pbbph3...
With all the programs on TV this last week or so about the
Titanic, I happened to catch a bit of one that started with
the distress message from Titanic.
The purported message was in Morse and was a series of
'hissing' pulses on a quite background.
On reflection, I realized that I have no idea what code
reception would have sounded like on the Marconi system in
April of 1912. Firstly, the detector was, I believe, either
a coherier or the Marconi metal tape unit, although on the
other ships it may have been a 'crystal' detector. In any
case I doubt that you would hear the hiss of the arc of the
transmitter, but I don't know what you would hear in the
earphones from those various detectors. Also, with the
relatively broadband receivers, I would assume the
'atmospherics' would have been substantial, but again, no
idea what that would sound like.
Lastly, I seem to recall that in the early days, the code
used was not Morse but a special Marconi code.
Anyone on this NG know what reception would have really
sounded like on April 15, 1912??
Neil S.
There is a pretty good article on the Titanic's radio
set up at:
The transmitter was a 5KW rotary arc. Keep in mind
that the transmissions were not continuous waves but
modulated by the arc. The received signal would have had an
audio tone determined by the arc rotation rate probably
around 500 hz.
The receiver on the Titanic was of the Marconi magnetic
type which replaced the coherer used previously on Marconi
ships. The Titanic also had a back-up tube receiver.
The code was "continental" code AKA international code,
the same as is used today. American Morse was used by some
US stations and ships very early on but never on British
ships. The only special code was the U.S. Navy code, also
used only very early on.
The initial distress message carried the Marconi prefix
if CQD, meaning CQ (seek you) distress but after a few
tried the operators switched to the new international
distress signal SOS. SOS has no meaning, it was chosen (by
the Germans BTW) because it is very distinctive ... _ _ _
... The instructions say to exaggerate the dashes.
The first link above has a further link to written
records of the Titanic distress traffic.
Whoever decided on the hissing pulses didn't do their
homework.
There is a very great deal about the Titanic and its
wireless equipment in the literature.
--
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
"nesesu" <neil_sutcli...@telus.net> wrote in message
news:11744688.363.1334517720064.JavaMail.geo-discussion-forums@pbbph3...
With all the programs on TV this last week or so about the Titanic, I happened to catch a bit of one that started with the distress message from Titanic.
The purported message was in Morse and was a series of 'hissing' pulses on a quite background.
On reflection, I realized that I have no idea what code reception would have sounded like on the Marconi system in April of 1912. Firstly, the detector was, I believe, either a coherier or the Marconi metal tape unit, although on the other ships it may have been a 'crystal' detector. In any case I doubt that you would hear the hiss of the arc of the transmitter, but I don't know what you would hear in the earphones from those various detectors. Also, with the relatively broadband receivers, I would assume the 'atmospherics' would have been substantial, but again, no idea what that would sound like.
Lastly, I seem to recall that in the early days, the code used was not Morse but a special Marconi code.
Anyone on this NG know what reception would have really sounded like on April 15, 1912??
Neil S.
A century ago it was happening NOW. God Bless all those who lost their lives and God Bless the survivors (there are no more) and a moment of silence for remembrance.
--
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
On Sun, 15 Apr 2012, George Conklin wrote:
> Here is a BBC clip. I looked it up through QST.
> Wireless operators originally used Marconi's "CQD" distress signal. "CQ" was
> the signal to stop transmission and pay attention.
Well no. "CQ" is a call to any station. Most traffic is point to point, so you have the station you are calling. But in an emergency, or in amateur radio where you just want to talk to anyone, you arent' looking for anyone specific, you are looking for a response.
> The "D" was added to
> signal distress. In 1906 the International Radio Telegraphic Convention in
> Berlin created the signal "SOS" for summoning assistance. The letters were
> chosen for their simplicity in Morse Code - three dots, three dashes and
> three dots. While the "SOS" superseded "CQD" in 1908 Marconi operators
> rarely used it. It became standard after the sinking of the Titanic.
On Sun, 15 Apr 2012, Richard Knoppow wrote:
> The initial distress message carried the Marconi prefix
> if CQD, meaning CQ (seek you) distress but after a few
> tried the operators switched to the new international
> distress signal SOS. SOS has no meaning, it was chosen (by
> the Germans BTW) because it is very distinctive ... _ _ _
> ... The instructions say to exaggerate the dashes.
An important consideration is that "SOS" isnt' really. It looks like
the three letters, but is sent as one character, no spacing, so it's actually a very special character, rather than three letters. It's either misuse or convenience that it gets called "SOS".
> "nesesu" <neil_sutcli...@telus.net> wrote in message
> news:11744688.363.1334517720064.JavaMail.geo-discussion-forums@pbbph3...
> With all the programs on TV this last week or so about the
> Titanic, I happened to catch a bit of one that started with
> the distress message from Titanic.
> The purported message was in Morse and was a series of
> 'hissing' pulses on a quite background.
> On reflection, I realized that I have no idea what code
> reception would have sounded like on the Marconi system in
> April of 1912. Firstly, the detector was, I believe, either
> a coherier or the Marconi metal tape unit, although on the
> other ships it may have been a 'crystal' detector. In any
> case I doubt that you would hear the hiss of the arc of the
> transmitter, but I don't know what you would hear in the
> earphones from those various detectors. Also, with the
> relatively broadband receivers, I would assume the
> 'atmospherics' would have been substantial, but again, no
> idea what that would sound like.
> Lastly, I seem to recall that in the early days, the code
> used was not Morse but a special Marconi code.
> Anyone on this NG know what reception would have really
> sounded like on April 15, 1912??
> Neil S.
> There is a pretty good article on the Titanic's radio
> set up at:
> The transmitter was a 5KW rotary arc. Keep in mind
> that the transmissions were not continuous waves but
> modulated by the arc. The received signal would have had an
> audio tone determined by the arc rotation rate probably
> around 500 hz.
> The receiver on the Titanic was of the Marconi magnetic
> type which replaced the coherer used previously on Marconi
> ships. The Titanic also had a back-up tube receiver.
> The code was "continental" code AKA international code,
> the same as is used today. American Morse was used by some
> US stations and ships very early on but never on British
> ships. The only special code was the U.S. Navy code, also
> used only very early on.
> The initial distress message carried the Marconi prefix
> if CQD, meaning CQ (seek you) distress but after a few
> tried the operators switched to the new international
> distress signal SOS. SOS has no meaning, it was chosen (by
> the Germans BTW) because it is very distinctive ... _ _ _
> ... The instructions say to exaggerate the dashes.
> The first link above has a further link to written
> records of the Titanic distress traffic.
> Whoever decided on the hissing pulses didn't do their
> homework.
> There is a very great deal about the Titanic and its
> wireless equipment in the literature.
> --
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickb...@ix.netcom.com
The current issue of the National Geographic contains more information on the state of the radio room as it exists today. For example, apparently the switches are still there, and are open.
I have a question. How exactly was the broadcast frequency regulated with a spark gap transmitter. Since spark gaps create a wide range of frequencies, how was a 600 meter frequency decided on, and how was the spark gap "tuned" to that. Was it through the antenna? After all, 500 mHZ is not exactly what you would call a long-distance frequency today.
Receivers used what to rectify the signal? Crystal sets, I know them. What did Marconi use?
> The transmitter was a 5KW rotary arc. Keep in mind
> that the transmissions were not continuous waves but
> modulated by the arc.
A bit of confusion here. It is not -- strictly speaking -- correct to say
the arc was "modulated". An arc transmitter didn't produce /any/ output
until it was keyed. *
This is why the "modern" system of code transmission is called (very
confusingly) continuous-wave -- CW. The RF is always being generated, with
the key modulating it.
* Mathematically, of course, this /is/ modulation.
> How was the broadcast frequency regulated with a spark gap transmitter?
> Since spark gaps create a wide range of frequencies, how was a 600m
> frequency decided on, and how was the spark gap "tuned" to that?
> Was it through the antenna? After all, 500 mHZ [sic -- MHz] is not exactly
> what you would call a long-distance frequency today.
Your decimal point is off. It's 500kHz, not megahertz.
I have a question. How exactly was the broadcast frequency regulated with a
spark gap transmitter. Since spark gaps create a wide range of frequencies,
how was a 600 meter frequency decided on, and how was the spark gap "tuned"
to that. Was it through the antenna? After all, 500 mHZ is not exactly
what you would call a long-distance frequency today.
Tuning the spark wasn't difficult at all. As the spark is much like a square wave, in that it has many MANY harmonics. The tuned tank simply tuned to use a specific harmonic (or group of harmonics). It was an energy wasteful way of doing it, but it worked. Tesla coils work on much the same principle. Not sure when the transition started, but somewhere along the line land based transmitters went to using AC generators at the direct carrier frequency (until the electronic oscillator came into its own).
BTW, it was 500 KHz, which is still to this day used as a marine beacon frequency (at least on special occasions).
>> The transmitter was a 5KW rotary arc. Keep in mind
>> that the transmissions were not continuous waves but
>> modulated by the arc.
> A bit of confusion here. It is not -- strictly speaking -- correct to say
> the arc was "modulated". An arc transmitter didn't produce /any/ output
> until it was keyed. *
> This is why the "modern" system of code transmission is called (very
> confusingly) continuous-wave -- CW. The RF is always being generated, with
> the key modulating it.
> * Mathematically, of course, this /is/ modulation.
>> How was the broadcast frequency regulated with a spark gap transmitter?
>> Since spark gaps create a wide range of frequencies, how was a 600m
>> frequency decided on, and how was the spark gap "tuned" to that?
>> Was it through the antenna? After all, 500 mHZ [sic -- MHz] is not >> exactly
>> what you would call a long-distance frequency today.
> Your decimal point is off. It's 500kHz, not megahertz.
Sorry about the decimal. But how was the frequency limited since spark gaps cover a huge frequency spread.
> I have a question. How exactly was the broadcast frequency regulated with > a
> spark gap transmitter. Since spark gaps create a wide range of > frequencies,
> how was a 600 meter frequency decided on, and how was the spark gap > "tuned"
> to that. Was it through the antenna? After all, 500 mHZ is not exactly
> what you would call a long-distance frequency today.
> Tuning the spark wasn't difficult at all. As the spark is much like a > square wave, in that it has many MANY harmonics. The tuned tank simply > tuned to use a specific harmonic (or group of harmonics). It was an energy > wasteful way of doing it, but it worked. Tesla coils work on much the same > principle. Not sure when the transition started, but somewhere along the > line land based transmitters went to using AC generators at the direct > carrier frequency (until the electronic oscillator came into its own).
> BTW, it was 500 KHz, which is still to this day used as a marine beacon > frequency (at least on special occasions).
I read that even during World War II very long wave transmitters for submarines still used AC generators to generate the fundamental frequency.
> The current issue of the National Geographic contains more information on
> the state of the radio room as it exists today. For example, apparently the
> switches are still there, and are open.
> I have a question. How exactly was the broadcast frequency regulated with a
> spark gap transmitter. Since spark gaps create a wide range of frequencies,
> how was a 600 meter frequency decided on, and how was the spark gap "tuned"
> to that. Was it through the antenna? After all, 500 mHZ is not exactly
> what you would call a long-distance frequency today.
It was too early for much regulation. Ship board radio was just really starting out, one of the first concrete uses for the otherwise lab curiosity of radio. Maybe it was mandatory at that point for ships to have radio, but if so it was a relatively new thing.
Spark gap transmitters were relatively broadband. There really wasn't much control, over the transmitters, frequency, or usage.
It was the Titanic sinking that caused real radio regulations to come into effect. The Radio Act of 1912 came later that year in the US (and other coutnries followed), which got those obnoxious amateurs out of the way (cast out to the useless frequencies above 200metres, about the top of the current AM braodcast band). The useful frequencies were reserved for serious use, shipboard radio being the most obvious. Remember, radio broadcasting didn't arrive until about 1922 (somewhat earlier if you take someone else's claim)
>> Sorry about the decimal. But how was the frequency >> limited
>> since spark gaps cover a huge frequency spread?
> That's a different question. I'd like to hear the answer, > myself.
Pretty much only by the selectivity of the tank circuit and antenna tuner. Its detailed in many places. Many early arc and spark transmitters could not be keyed on and off, rather the tuning of the output tank was changed by keying turns on the coil. This could be done directly (see the extra large spark keys) or by a relay. One of the great problems with early wireless was the very broad signals and that the key-up signal was just shifted over. Eventually, a single frequency method of keying was developed. According to Howeth's book, _The History of Communications-Electronics in the United States Navy_ by a U.S. Navy engineer. This was called uniwave signaling.
This book is available on-line free and is a great source of early wireless history.
I am currently reading about five books on the history of radio, a fascinating mixture of technology, politics, finance, greed, all the elements of a new industry.
--
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
>> I have a question. How exactly was the broadcast >> frequency regulated with a
>> spark gap transmitter. Since spark gaps create a wide >> range of frequencies,
>> how was a 600 meter frequency decided on, and how was the >> spark gap "tuned"
>> to that. Was it through the antenna? After all, 500 mHZ >> is not exactly
>> what you would call a long-distance frequency today.
>> Tuning the spark wasn't difficult at all. As the spark is >> much like a square wave, in that it has many MANY >> harmonics. The tuned tank simply tuned to use a specific >> harmonic (or group of harmonics). It was an energy >> wasteful way of doing it, but it worked. Tesla coils work >> on much the same principle. Not sure when the transition >> started, but somewhere along the line land based >> transmitters went to using AC generators at the direct >> carrier frequency (until the electronic oscillator came >> into its own).
>> BTW, it was 500 KHz, which is still to this day used as a >> marine beacon frequency (at least on special occasions).
> I read that even during World War II very long wave > transmitters for submarines still used AC generators to > generate the fundamental frequency.
I think these were holdover Alexanderson alternators. Some as large as 200,000 watts were built, mostly for frequencies below about 100 KHz. There is only one left in existence, in Sweden. Its fired up once a year. Alternators put out true CW, that is, a single frequency. They continued to be used after vacuum tube transmitters supplanted all other types because for the power they put out they were very satisfactory and replacing them would have been expensive.
Very low frequencies penetrate sea water and can be received underwater with relatively short antennas. Currently, the United States Navy maintains two very high power transmitters operating in the range between about 10khz and 15 khz for communication with submerged submarines. Also, these VLF frequencies have the property of being phase stable so they can be used for extremely accurate time, frequency, and navigation data.
--
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
>> The current issue of the National Geographic contains >> more information on
>> the state of the radio room as it exists today. For >> example, apparently the
>> switches are still there, and are open.
>> I have a question. How exactly was the broadcast >> frequency regulated with a
>> spark gap transmitter. Since spark gaps create a wide >> range of frequencies,
>> how was a 600 meter frequency decided on, and how was the >> spark gap "tuned"
>> to that. Was it through the antenna? After all, 500 mHZ >> is not exactly
>> what you would call a long-distance frequency today.
> It was too early for much regulation. Ship board radio > was just really starting out, one of the first concrete > uses for the otherwise lab curiosity of radio. Maybe it > was mandatory at that point for ships to have radio, but > if so it was a relatively new thing.
> Spark gap transmitters were relatively broadband. There > really wasn't much control, over the transmitters, > frequency, or usage.
> It was the Titanic sinking that caused real radio > regulations to come into effect. The Radio Act of 1912 > came later that year in the US (and other coutnries > followed), which got those obnoxious amateurs out of the > way (cast out to the useless frequencies above 200metres, > about the top of the current AM braodcast band). The > useful frequencies were reserved for serious use, > shipboard radio being the most obvious. Remember, radio > broadcasting didn't arrive until about 1922 (somewhat > earlier if you take someone else's claim)
> Michael
Broadcasting was done experimentally before WW-1 but the control of all wireless by the government stopped it until about 1919 when wireless was released again to private hands. Since there had been great development in practical vacuum tube transmitters and receivers broadcasting of voice and music was much more practical following the war. One of the primary experimenters was Dr. Frank Conrad, of the Westinghouse company who began fairly regular transmissions around 1919. By the end of 1920 it became evident that broadcasting was practical and the United States Department of Commerce began to issue licenses for commercial broadcasting stations about the end of 1920. Westinghouse obtained the first three licenses issued and four of the first dozen or so. The stations were KDKA, Pittsburgh; WBZ, Boston; and WJZ, New York. The last was KYA, originally issued for Chicago but moved later to Philadelphia. All these were issued in December of 1920. Quite a large number of licenses were issued in 1921 but 1922 saw an explosion in stations and home receivers. There is a great deal of history available both in books and on the web. The early radio bulletins which list all stations licensed by the U.S. Government are available at the FCC web site.
--
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
> The transmitter was a 5KW rotary arc. Keep in mind
> that the transmissions were not continuous waves but
> modulated by the arc. The received signal would have had an
> audio tone determined by the arc rotation rate probably
> around 500 hz.
Sounds about right. I recall from somewhere that it was 300 Hz...
need to check.
Cheers,
Roger
> >> I have a question. How exactly was the broadcast
> >> frequency regulated with a
> >> spark gap transmitter. Since spark gaps create a wide
> >> range of frequencies,
> >> how was a 600 meter frequency decided on, and how was the
> >> spark gap "tuned"
> >> to that. Was it through the antenna? After all, 500 mHZ
> >> is not exactly
> >> what you would call a long-distance frequency today.
> >> Tuning the spark wasn't difficult at all. As the spark is
> >> much like a square wave, in that it has many MANY
> >> harmonics. The tuned tank simply tuned to use a specific
> >> harmonic (or group of harmonics). It was an energy
> >> wasteful way of doing it, but it worked. Tesla coils work
> >> on much the same principle. Not sure when the transition
> >> started, but somewhere along the line land based
> >> transmitters went to using AC generators at the direct
> >> carrier frequency (until the electronic oscillator came
> >> into its own).
> >> BTW, it was 500 KHz, which is still to this day used as a
> >> marine beacon frequency (at least on special occasions).
> > I read that even during World War II very long wave
> > transmitters for submarines still used AC generators to
> > generate the fundamental frequency.
> I think these were holdover Alexanderson alternators.
> Some as large as 200,000 watts were built, mostly for
> frequencies below about 100 KHz. There is only one left in
> existence, in Sweden. Its fired up once a year.
> Alternators put out true CW, that is, a single frequency.
> They continued to be used after vacuum tube transmitters
> supplanted all other types because for the power they put
> out they were very satisfactory and replacing them would
> have been expensive.
> Very low frequencies penetrate sea water and can be
> received underwater with relatively short antennas.
> Currently, the United States Navy maintains two very high
> power transmitters operating in the range between about
> 10khz and 15 khz for communication with submerged
> submarines. Also, these VLF frequencies have the property
> of being phase stable so they can be used for extremely
> accurate time, frequency, and navigation data.
> --
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickb...@ix.netcom.com
Correct, of course, about rotary generator CW Tx... they came after
Titanic.
The Titanic main Tx was a 5 KW motor generator set producing, IIRC,
300Hz AC to a step up transformer, thence to a synchronized, rotary
spark gap. I presume a crystal or Fleming valve detector would give a
300 Hz keyed tone plus hash to the phones. The transmitted wavelength
was determined by a low-Q antenna tank circuit and antenna
dimensions... given the wide RF band coming off the spark I imagine it
was quite a broad "channel".
BTW, the emergency Tx was a keyed induction coil (the telegraph key
switches, via a relay, the coil "buzzer" contact that runs at natural
frequency to deliver a steam of sparks), the secondary spark went to
the antenna, one one side and ground on the other. Not sure if there
was a tank cct in there. One Marconi Tx used 10 inch coil with, from
memory, around 125 watts of primary power but only a fraction of that
would get radiated as a signal. I've forgotten how big the Titanic
emergency spark coil was... many gaps to fill here, so I defer to
others!
Cheers,
Roger
> With all the programs on TV this last week or so about the Titanic, I happened to catch a bit of one that started with the distress message from Titanic.
> The purported message was in Morse and was a series of 'hissing' pulses on a quite background.
> On reflection, I realized that I have no idea what code reception would have sounded like on the Marconi system in April of 1912. Firstly, the detector was, I believe, either a coherier or the Marconi metal tape unit, although on the other ships it may have been a 'crystal' detector. In any case I doubt that you would hear the hiss of the arc of the transmitter, but I don't know what you would hear in the earphones from those various detectors. Also, with the relatively broadband receivers, I would assume the 'atmospherics' would have been substantial, but again, no idea what that would sound like.
> Lastly, I seem to recall that in the early days, the code used was not Morse but a special Marconi code.
> Anyone on this NG know what reception would have really sounded like on April 15, 1912??
> Neil S.
I suspect it would sound like Modulated CW. dits and dahs of pleasant bass tones. Old Morse had been replaced by International Morse, but is still Morse.
There is a great deal of information on early equipment at:
http://earlyradiohistory.us/ and to other sites he links to. One can also find several old technical books at:
The audio modulation of a _rotary arc_ was due to the periodicty of the rotator. Typically this was some mid audio frequency, say from 300 to 800 hz. A plain arc was usually driven by raw AC so its tone was the alternating frequency of the generator, also generally a mid- frequency tone.
Arc converters, AKA the Poulsen arc, was a CW transmitter, with no modulation. The Poulsen arc was the most popular transmitter before vacuum tubes took over. The Alexanderson alternator was also a CW machine. These were much larger and more expensive than a Poulsen arc for a given power.
Arc transmitters can be devided into damped and undamped arcs. The undamped arc produces CW, an undamped arc produces a pulsed signal which is very broad band.
Spark transmitters produce damped waves. A number of variations of spark gaps were used varying from the simplest to multiple plate gaps to handle very high power. All depended on the tank circuit and antenna to select the output frequency and were modulated by the power supply.
One of Marconi's most valuable patents was the "four sevens" patent (British patent number 7777) for a triple tuned circuit that had enough selectivity to make these early transmitters and receivers practical.
The Early Radio site has articles on all of these types plus a Google search for any of them will find many articles. I think the Early Radio site has diagrams of arc and spark transmitters and shows how they were keyed.
All of this stuff was pretty crude.
At the time of the Titanic sinking there was no official distress frequency, 500Khz came later. Most maritime communication was in what is now the broadcast band and down to around 100 khz for long distance work.
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
> The transmitter was a 5KW rotary arc. Keep in mind
> that the transmissions were not continuous waves but
> modulated by the arc. The received signal would have had > an
> audio tone determined by the arc rotation rate probably
> around 500 hz.
Sounds about right. I recall from somewhere that it was 300 Hz...
need to check.
Cheers,
Roger
> On 04/15/2012 12:22 PM, nesesu wrote:
>> With all the programs on TV this last week or so about >> the Titanic, I happened to catch a bit of one that >> started with the distress message from Titanic.
>> The purported message was in Morse and was a series of >> 'hissing' pulses on a quite background.
>> On reflection, I realized that I have no idea what code >> reception would have sounded like on the Marconi system >> in April of 1912. Firstly, the detector was, I believe, >> either a coherier or the Marconi metal tape unit, >> although on the other ships it may have been a 'crystal' >> detector. In any case I doubt that you would hear the >> hiss of the arc of the transmitter, but I don't know what >> you would hear in the earphones from those various >> detectors. Also, with the relatively broadband receivers, >> I would assume the 'atmospherics' would have been >> substantial, but again, no idea what that would sound >> like.
>> Lastly, I seem to recall that in the early days, the code >> used was not Morse but a special Marconi code.
>> Anyone on this NG know what reception would have really >> sounded like on April 15, 1912??
>> Neil S.
> I suspect it would sound like Modulated CW. dits and dahs > of pleasant bass tones. Old Morse had been replaced by > International Morse, but is still Morse.
Something like MCW but the carrier is either keyed or shifted. The early keying was a sort of frequency shift keying with the modulated carrier being present all the time. Keyed MCW, was used for distress traffic for many years. The autoalarms made by MacKay Radio were operated by the modulation while those made by RCA worked on carrier only. I still remember the local RCA station, KSE, calling for traffic on 500khz with a modulated transmitter. The modulation came up slowly, I suspect the filament in the oscillator warming up. I never had the nerve to try to arrange a visit. The station was in Torrance with a big flat top antenna supported by a couple of self-supporting towers. When I saw it there was a horse grazing there. KSE was the only station I remember on 500khz with MCW but I could not hear many.
The autoalarm requried a series of 4 second dashes separated by one second. Depending on the make it required either four or five successive dashes in a minute to go off. Radio room clocks had markings around the second scale for hand keying the autoalarm signal although the alarm itself had a clock work keyer. The autoalarm signal would be followed by the conventional SOS and a message concerning the nature of the problem and the ship's name and position, etc.
--
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
> "dave"<d...@dave.dave> wrote in message
> news:xbadnbkhp5-rxBHSnZ2dnUVZ_omdnZ2d@earthlink.com...
>> On 04/15/2012 12:22 PM, nesesu wrote:
>>> With all the programs on TV this last week or so about
>>> the Titanic, I happened to catch a bit of one that
>>> started with the distress message from Titanic.
>>> The purported message was in Morse and was a series of
>>> 'hissing' pulses on a quite background.
>>> On reflection, I realized that I have no idea what code
>>> reception would have sounded like on the Marconi system
>>> in April of 1912. Firstly, the detector was, I believe,
>>> either a coherier or the Marconi metal tape unit,
>>> although on the other ships it may have been a 'crystal'
>>> detector. In any case I doubt that you would hear the
>>> hiss of the arc of the transmitter, but I don't know what
>>> you would hear in the earphones from those various
>>> detectors. Also, with the relatively broadband receivers,
>>> I would assume the 'atmospherics' would have been
>>> substantial, but again, no idea what that would sound
>>> like.
>>> Lastly, I seem to recall that in the early days, the code
>>> used was not Morse but a special Marconi code.
>>> Anyone on this NG know what reception would have really
>>> sounded like on April 15, 1912??
>>> Neil S.
>> I suspect it would sound like Modulated CW. dits and dahs
>> of pleasant bass tones. Old Morse had been replaced by
>> International Morse, but is still Morse.
> Something like MCW but the carrier is either keyed or
> shifted. The early keying was a sort of frequency shift
> keying with the modulated carrier being present all the
> time. Keyed MCW, was used for distress traffic for many
> years. The autoalarms made by MacKay Radio were operated by
> the modulation while those made by RCA worked on carrier
> only. I still remember the local RCA station, KSE, calling
> for traffic on 500khz with a modulated transmitter. The
> modulation came up slowly, I suspect the filament in the
> oscillator warming up. I never had the nerve to try to
> arrange a visit. The station was in Torrance with a big
> flat top antenna supported by a couple of self-supporting
> towers. When I saw it there was a horse grazing there. KSE
> was the only station I remember on 500khz with MCW but I
> could not hear many.
> The autoalarm requried a series of 4 second dashes
> separated by one second. Depending on the make it required
> either four or five successive dashes in a minute to go off.
> Radio room clocks had markings around the second scale for
> hand keying the autoalarm signal although the alarm itself
> had a clock work keyer. The autoalarm signal would be
> followed by the conventional SOS and a message concerning
> the nature of the problem and the ship's name and position,
> etc.
I remember the Autoalarm from Radiotelephone Operator exam Element 2.
> There is a great deal of information on early equipment at:
> http://earlyradiohistory.us/ > and to other sites he links to. One can also find several old technical > books at:
> The audio modulation of a _rotary arc_ was due to the periodicty of > the rotator. Typically this was some mid audio frequency, say from 300 to > 800 hz. A plain arc was usually driven by raw AC so its tone was the > alternating frequency of the generator, also generally a mid- frequency > tone.
> Arc converters, AKA the Poulsen arc, was a CW transmitter, with no > modulation. The Poulsen arc was the most popular transmitter before > vacuum tubes took over. The Alexanderson alternator was also a CW > machine. These were much larger and more expensive than a Poulsen arc for > a given power.
> Arc transmitters can be devided into damped and undamped arcs. The > undamped arc produces CW, an undamped arc produces a pulsed signal which > is very broad band.
> Spark transmitters produce damped waves. A number of variations of > spark gaps were used varying from the simplest to multiple plate gaps to > handle very high power. All depended on the tank circuit and antenna to > select the output frequency and were modulated by the power supply.
> One of Marconi's most valuable patents was the "four sevens" patent > (British patent number 7777) for a triple tuned circuit that had enough > selectivity to make these early transmitters and receivers practical.
> The Early Radio site has articles on all of these types plus a Google > search for any of them will find many articles. I think the Early Radio > site has diagrams of arc and spark transmitters and shows how they were > keyed.
> All of this stuff was pretty crude.
> At the time of the Titanic sinking there was no official distress > frequency, 500Khz came later. Most maritime communication was in what is > now the broadcast band and down to around 100 khz for long distance work.
