| Author
| Message
|
    
Inger Sheil
Moderator
Username: isheil
Post Number: 2827
Registered: 12-2000
| | Posted on Monday, March 20, 2006 - 1:19 am: |       |
Fingers crossed for Autumn, Parks - but as it looks like the information is still coming in steadily and expanding your knowledge and interpretation all the time, I'm content to wait until you feel it's ready to go! |
Parks Stephenson
Member
Username: sparks
Post Number: 1997
Registered: 4-2001
| | Posted on Monday, March 20, 2006 - 6:08 am: | |
Ing,
As you probably know, it's hard to draw the line and commit yourself. But, I know that it's got to be done and so it will be. Some day.
Parks
http://marconigraph.com |
Robert T. Paige
Member
Username: jnb
Post Number: 345
Registered: 5-2005
| | Posted on Saturday, April 1, 2006 - 12:12 am: | |
Assuming that Phillips had been working Cape Race just prior to the collision....would Cape Race have picked up the Titanic's CQD/SOS and relayed it (re-transmitted it) ? This is a point that all the Titanic movies fail to mention ?
"The best I've seen, ma'am....Hardly any rats."
Robert T. Paige
32 51' 18" N 97 00' 18" W
|
Robert T. Paige
Member
Username: jnb
Post Number: 346
Registered: 5-2005
| | Posted on Saturday, April 1, 2006 - 12:26 am: | |
There was also a story (Probably should check into this more before posting this) that a young David Sarnoff picked up Titanic's distress message in New York. Just for the sake of my own fiction, would it have been possible to have been received at Cedar Rapids, Iowa by a young teen-aged "Ham Radio Operator" named "Ben Calvert" ?
I was going to write Arthur A. Collins into the story, but he would have only been 3 years old in 1912.....He would have to have been even more of a "wireless" child prodigy than he was later when he was 15 years old ? LOL.
"The best I've seen, ma'am....Hardly any rats."
Robert T. Paige
32 51' 18" N 97 00' 18" W
|
Robert T. Paige
Member
Username: jnb
Post Number: 351
Registered: 5-2005
| | Posted on Wednesday, April 5, 2006 - 4:17 am: | |
Michael Standart, Parks Stephenson..and others in the field of expertise :
PS- In the "I have heard" category, "I have heard" there was unusual aurora borealis and other atmospheric activity that night affecting "wireless " on the late night and early morning hours of 14-15 April 1912.
Could the Titanic's signals have been heard in other parts of the world due to "skip" conditions ? Were there any reports of this in historic records ?
"The best I've seen, ma'am....Hardly any rats."
Robert T. Paige
32 51' 18" N 97 00' 18" W
|
Parks Stephenson
Member
Username: sparks
Post Number: 2007
Registered: 4-2001
| | Posted on Wednesday, April 5, 2006 - 5:59 am: | |
Robert,
Sorry, I was occupied elsewhere.
To answer your question about Sarnoff, people who repeat the myth often forget that Wanamaker's (where his station was located) was closed on Sunday. Sarnoff would have arrived Monday morning, in time to receive messages relayed from other ships and shore stations. He did not hear Titanic's call directly. Read "Empire of the Air" for a factual look at Sarnoff and the early days of wireless.
So many wireless stations, both land-based and sea-borne, professional and amateur, began buzzing with news of the disaster on the morning of the 15th that it's impossible to track the path that the news took to the public. Ships relayed information, land stations picked them up and passed them along. The clamour and confusion got so bad that the American Marconi Co. asked the US Government to close down all stations north of Hatteras, except for 4 stations to handle Carpathia exclusively. Department of Justice officials raced around, trying to trace the origin of unauthorised signals. Read "SOS to the Rescue" for more on this.
I am not aware of any reports of Titanic's signals being directly received by anyone other than the ships in the area. Some may have been outside Titanic's theoretical range.
Parks
http://marconigraph.com |
Michael H. Standart
Moderator
Username: mstandart
Post Number: 9702
Registered: 12-2000
| | Posted on Wednesday, April 5, 2006 - 6:34 am: | |
>>Could the Titanic's signals have been heard in other parts of the world due to "skip" conditions ?<<
If what "You Heard" is accurate, it's possible as far as I know. I can't say for sure since I'm no expert on radio technology. Like Parks, I'm not aware of any accounts of the Titanic's signals being recieved by anyone outside of the ship's range. That doesn't mean there isn't some notation sitting forgotten in some dusty old station log, but if it's there, it hasn't seen daylight in 94 years.
Cordially,
Michael H. Standart
Equal Opportunity Curmudgeon |
Parks Stephenson
Member
Username: sparks
Post Number: 2008
Registered: 4-2001
| | Posted on Wednesday, April 5, 2006 - 3:42 pm: | |
>That doesn't mean there isn't some notation sitting forgotten in some dusty old station log, but if it's there, it hasn't seen daylight in 94 years.
Or it could be that our research is not thorough enough.
Parks
http://marconigraph.com |
Samuel Halpern
Member
Username: cmdrsam
Post Number: 1026
Registered: 3-2003
| | Posted on Thursday, April 6, 2006 - 1:33 am: | |
This discussion of skip distances, etc., brings me back to my earlier career days at Bell Labs when I worked in a radio research department in Holmdel, NJ. What I could say about propagation at Medium Frequencies (300 to 3000 KHz ) is that nighttime range was far greater than daytime range by about two to three times because of sky wave propagation; that is refraction off the F layer of the ionosphere. During the day, distance is limited by what we call ground wave propagation. There is no sky wave during the day at these frequencies because of absorption by the D layer which disappears at night. On occasion, there can be multiple hops at night between the ionosphere and the Earth extending coverage to very great distances. Usually, there is much more propagation loss in these multiple hop cases requiring very sensitive receivers to detect the transmissions, something not readily available in 1912.
The term "skip distance" is usually used in the wrong sense. It is the distance from the transmitter to the point where the sky wave is first returned to Earth. The skip zone is a region of silence, a dead zone, between the point where the ground wave becomes too weak to be detected and the point where the sky wave is first returned to Earth. When the skip distance is short enough that there is no zone of silence, then there is no skip zone. However, in a region where the sky wave and ground wave may be of near equal intensity, there could be severe fading caused by the sky wave alternately reinforcing and canceling the ground wave. This is due to the longer path that the sky wave has to travel that brings it in and out of phase with the ground wave. This, at times, would make it difficult to detect signals in addition to any other impairments caused by interference from other stations fading in and out, as well as any added atmospheric noise disturbances.
The energetic particles that come from the sun to create the visible aurora alter the ionospheric layers that affect radio propagation. These incoming particles cause rapid radio signal fading called fluttering as a result of changes to the multiple paths that the radio waves take during these disturbances. During some peak sunspot periods, variations in the Earth’s magnetic field up to about 2 degrees have been reported. 1912, as it turned out, was not a year of peak sunspot activity or magnetic disturbance. Nevertheless, the aurora borealis was very much active the night of April 14, 1912 as reported by several passengers that took to the lifeboats (e.g., see Beesley’s account).
On the night of April 14th, conditions for radio reception were good but far from ideal. Consider what senior operator E. J. Moore in the Olympic wrote in his PV: “10.50 p.m. Hear Titanic signaling to some ship about striking an iceberg. Am not sure it is the Titanic who has struck an iceberg. Am interfered by atmospherics and many stations working.”
Also, to my knowledge, Cape Race was the only land station that directly picked up Titanic's 500 kHz transmissions that night.
There are no Unsinkable Theories.
Sam Halpern
40 23' 50'' N, 74 13' 55'' W. |
Dave Gittins
Member
Username: gittins
Post Number: 2666
Registered: 4-2001
| | Posted on Thursday, April 6, 2006 - 3:54 am: | |
Sam, could this skip distance explain something that's long puzzled me. Apart from Virginian's very late reception of CQ, all the other ships seem to have lost contact with Titanic well before she sank. Yet we are told Phillips kept repeating his distress calls to the end.
Could there have been some kind of dead zone within 40 - 50 miles of Titanic?
Dave Gittins
Titanic: Monument and Warning.
http://users.senet.com.au/~gittins/Book.html |
Samuel Halpern
Member
Username: cmdrsam
Post Number: 1032
Registered: 3-2003
| | Posted on Friday, April 7, 2006 - 1:13 am: | |
Hi Dave: The operating frequency for 600 meters (500 kHz) is below what is called the critical frequency. The critical frequency is the highest frequency that a signal if sent straight up vertically will be refracted straight down. So at 500 kHz at night you will have sky waves that are refracted at all angles and theoretically there should not be any skip zone. But if the there is some variations in the density of the F layer there can be some angles that refract differently creating some weird coverage effects, or so I heard.
As I mentioned in the above post, you can and do get regions of signal fade caused by destructive interference between ground wave and sky wave, or even between a double hop sky wave and a single sky hop wave. As far as the ability to receive Titanic's signals, the received signals would start to get lost in the background noise as the transmitting power was getting weaker near the end. Once the power became so low as to not support the development of a spark, transmission would simply come to a complete end.
If I remember correctly, Bride said that Philips continued to send for a short time after making his last contact. When it became clear that nobody was responding anymore, that is when he shut things down and abandoned the wireless cabin.
There are no Unsinkable Theories.
Sam Halpern
40 23' 50'' N, 74 13' 55'' W. |
Robert T. Paige
Member
Username: jnb
Post Number: 353
Registered: 5-2005
| | Posted on Friday, April 7, 2006 - 5:52 am: | |
>>I'm no expert on radio technology<<
Admittedly, neither am I. I'm strictly an amateur (with an FCC license to prove it ). However, all things considered, would it be fair to assume that anything, anywhere could have happened as far as to reception of Titanic's transmissions ?
>>When it became clear that nobody was responding anymore, that is when he shut things down and abandoned the wireless cabin.<<
Cape Race and/or Carpathia were no longer responding ? Some of the "movie versions" seem to imply that Titanic was in communication with Carpathia for several exchanges of transmissions up until the time that Titanic's power gave out ?
>>As far as the ability to receive Titanic's signals, the received signals would start to get lost in the background noise as the transmitting power was getting weaker near the end.<<
Nothing much on amplification on receivers in those days ....just detectors ?
"The best I've seen, ma'am....Hardly any rats."
Robert T. Paige
32 51' 18" N 97 00' 18" W
|
Samuel Halpern
Member
Username: cmdrsam
Post Number: 1034
Registered: 3-2003
| | Posted on Friday, April 7, 2006 - 3:42 pm: | |
Hi Robert. I'm not sure I would go as far as saying "anything or anywhere," but there is a lot of unpredictability when it comes to propagation because of the multipath environment that is created. (As an aside, even at the relatively short ranges at cellular frequencies in the 1 and 2 GHz bands, there is much multipath fading caused by local scattering of the received signals in the vicinity of the mobile. Because of the modulation methods and signal coding used, this is not much of a problem unless you are in a region of low average signal-to-interference ratio and you can't get handed off to another cell. And that's when your call gets dropped.)
As far as the receivers, they were essentially passive devices. The biggest problem in my opinion was that they were not very selective in terms of the bandwidth. The multiple tuners certainly could be tuned to a given frequency, anywhere from 120 kHz to 3 MHz, but their bandwidth was not very sharp and they therefore allowed a relative wide band of noise and interference to pass through compared say to what a superheterodyne receiver with multiple stages of amplification and passband filtering would allow. The other thing to keep in mind is the modulation method of wireless telegraphy was on-off keying, a simple form of amplitude modulation. Anything in the way of noise or interference was simply additive. If an interfering station came in at 1/3 the power of the desired signal (about 5 dB down) it was heard at 1/3 the level of the desired station, just like in AM radio broadcasting today with the automatic gain control cut out.
There are no Unsinkable Theories.
Sam Halpern
40 23' 50'' N, 74 13' 55'' W. |
Robert T. Paige
Member
Username: jnb
Post Number: 357
Registered: 5-2005
| | Posted on Saturday, April 8, 2006 - 4:39 am: | |
Samuel Halpern-
Has anyone ever estimated what the sensitivity and/or signal-to-noise/signal-to-signal plus noise ratio would have been for a Marconi detector ?
Or what the efficiency and/or effective radiated power would have been for the transmitter ?
Thanks again to you and all the others for the detailed explanations on this website.
-Robert
"The best I've seen, ma'am....Hardly any rats."
Robert T. Paige
32 51' 18" N 97 00' 18" W
|
Samuel Halpern
Member
Username: cmdrsam
Post Number: 1038
Registered: 3-2003
| | Posted on Saturday, April 8, 2006 - 5:32 pm: | |
Robert: I will defer to Parks Stephenson the specifics concerning the efficiency and ERP of the Titanic 5 kW installation. As far as sensitivity of the magnetic detector, I have not seen any quantified data on that. The pages from a very old book I have do state that the sensitivity was dependent on the setting of the magnets. This I can understand since the detection principle depended on setting up a magnetized state in the iron band opposite the magnetics poles as it passes near them which is retained due to the hysteresis effect. If RF oscillations are produced in a coil that is wound over the iron band it tends to to demagetize the band passing through it while these oscillations last. This creates a small demagnetized length of band. So as the band is moving across at 7 to 8 cm/sec with areas that are magnetized and other areas that are demagnetized it induces a current in the separate telephone coil that is also wound over the moving iron band. Then it depends on the sensitivity of the operator's ear to detect the sound. Strong RF oscillations will demagetize more of the iron than weak signals. Therefore a stronger induced current will be set up in the telephone coil and produce a louder sound. If the magnets are too close, weak signals would demagnitize the iron enough to be heard. If they are too far away, then the iron would not be magnitized enough and again weak signals would not be heard.
A good on-line description of the device can be found here: http://home.luna.nl/~arjan-muil/radio/Magnetic.html.
There are no Unsinkable Theories.
Sam Halpern
40? 23' 50'' N, 74? 13' 55'' W. |
Parks Stephenson
Member
Username: sparks
Post Number: 2017
Registered: 4-2001
| | Posted on Saturday, April 8, 2006 - 5:42 pm: | |
Sam,
The Marconi multiple tuner worked in 4 switched ranges: 80-150 metres, 150-1600 metres, 1600-2000 metres, and 2000-2600 metres. Converting to kilohertz, this gives a total range of 3.75 MHz to 115 kHz. This is very close to what you posted, but different enough to make me curious as to where you got your numbers.
Robert,
Even after it was invented, the exact manner in which the magnetic detector operated remained a mystery. It was not until 1931 that a new understanding of magnetic domains and domain physics helped to fully explain the Maggie's workings.
However, it was understood at the time (thanks to RN testing at its experimental station HMS Vernon) that the Maggie was primarily influenced by the amplitude of the first wave of a train of electromagnetic oscillations. Therefore, the duration or persistency of the signal didn't increase the apparent strength of the signal. This is why the Maggie was used only to detect spark transmissions...the energy in a spark transmission is concentrated in the initial burst, while the mean power output is relatively low. Other distrubances in the atmosphere (termed "X"s), could also be picked up by the detector.
In addition, the movement of the iron band itself past the stationary magnets created its own noise (a "hissing" or "breathing effect" that would later -- after 1922 -- become known as "Barkhausen noise"). This made the reading of weak signals difficult. The magnets could be arranged in an alternate position (switching the poles from S-N-N-S to N-S-N-S) to reduce the Barkhausen noise, but it also decreased the sensitivity of the detector. The arrangement was at the whim of the individual operator...some liked the standard arrangement because they were not bothered by the Barkhausen noise and used the noise as an indicator that the clockwork of the mechanism was still functioning properly. There isn't enough information to clue us into Phillips's personal preference, so I can't tell you how sensitive Titanic's detector was.
But none of this answers your question directly. I mention it to show how difficult it would be to determine the unit's sensitivity. There were no filters in the detector itself...it was influenced by any electromagnetic pulse in the atmosphere. The tuner provided some filtering, but not the kind you would be accustomed to in a modern CW set. It was a crude system, but the most effective and reliable during the spark age. Diode-valve detector sets were more sensitive, but not as reliable. Phillips never used Titanic's valve detector, as far as we know...it sat unused -- but in standby -- to the left (when facing aft) of the Maggie-tuner set, on the operator's desk.
I can't answer your question about efficiency or effective radiated power, because the spark transmitter was assessed according to different criteria. Since the function of a spark transmitter was to introduce an electromagnetic oscillation into the atmosphere, more attention at the time was focused on achieving the optimum wavelength. The contemporary equation for the power of waves (measured in watts) depended upon knowing the wavelength, height of aerial and transmitting current. From this, you can see that the radiated power is not only dependent on the power of the spark, but also the physical height of the antenna.
Parks
http://marconigraph.com |
Samuel Halpern
Member
Username: cmdrsam
Post Number: 1040
Registered: 3-2003
| | Posted on Saturday, April 8, 2006 - 8:25 pm: | |
Hi Parks. I was not trying to be precise. The tuner was noted to cover a range between 600 m and 2.5 Km in the paper describing the electrical equipment of the Olympic & Titanic from The Electrician. I just converted those wavelengths to frequencies.
I do have a copy of several pages from an old book on the subject. The chapter on "Apparatus of Radiotelegraphy" has quite a bit of detail in the section on Receiving Apparatus on tuners, magnetic detectors, etc. The Marconi multiple tuner is covered in great detail, including a description of a 5 step procedure used to adjusted the tuner to detect a given frequency.
There are no Unsinkable Theories.
Sam Halpern
40? 23' 50'' N, 74? 13' 55'' W. |
Parks Stephenson
Member
Username: sparks
Post Number: 2020
Registered: 4-2001
| | Posted on Saturday, April 8, 2006 - 8:46 pm: | |
Sam,
I'm always on the look for new source material, which is why I asked. I didn't recognise the frequency range from a source that I already have (then again, I didn't convert the range given in the Electrician article to kilohertz).
Parks
http://marconigraph.com |
Carla Velterop
Member
Username: carla
Post Number: 13
Registered: 3-2006
| | Posted on Thursday, May 4, 2006 - 1:12 pm: | |
Parks,
On a good, clear day, how far would the Titanic's wireless be able to transmit? I've read conflicting sets of digits, so I'm really unsure. Also, what would the configuration of the magnets (S-N-S-N or S-N-N-S) do to affect the quality of the messages received, if it did anything?
Carla |
Robert T. Paige
Member
Username: jnb
Post Number: 378
Registered: 5-2005
| | Posted on Saturday, May 6, 2006 - 2:35 am: | |
Parks-
Couple of layman's questions:
1. Would the placement or "tuning" of the magnets be something akin to adjusting or "tuning" of the old regenerative receivers ?
2.Would putting the rudder "hard astarboard" (or port) be something akin to turning the steering wheel of car hard to one side...something akin to skidding into the turn ?
Regards, and thanks again ,
Robert
"The best I've seen, ma'am....Hardly any rats."
Robert T. Paige
32 51' 18" N 97 00' 18" W
|
Robert T. Paige
Member
Username: jnb
Post Number: 397
Registered: 5-2005
| | Posted on Friday, May 26, 2006 - 9:10 pm: | |
There is also a comment on the "Movies" thread...
In ANTR, you can see that the drums are rotating on the detector, but in the 1997 Cameron movie they seem to be stationary...of course, if this was the case,no signals would have been received.
"The best I've seen, ma'am....Hardly any rats."
Robert T. Paige
32 51' 18" N 97 00' 18" W
|
Dan Waddell
Member
Username: danwaddell
Post Number: 3
Registered: 3-2011
| | Posted on Monday, June 13, 2011 - 1:57 pm: | |
Apologies for dredging this topic up, but it seems the best place to ask it - just when did the wireless break down? This thread seems to indicate it was the evening of Saturday April 13th, and it was fixed again for the following morning. However, I have seen several sources, not least the chronology on this site, which says the wireless broke down at some point during the evening of Friday 12th. Some say it was back working the next morning (13th) while others, again including the chronology on this site, suggests it was out for more than 24 hours and not working again until Sunday morning, the day of the collision.
Does anyone know definitively? |
Dan Waddell
Member
Username: danwaddell
Post Number: 4
Registered: 3-2011
| | Posted on Monday, June 13, 2011 - 3:07 pm: | |
Seems I have managed to answer my own question.
From the British Inquiry, Bride's testimony:
16791. Late on Saturday?
- From 11 o'clock Friday night till half-past four or five saturday morning.
Odd that so many sources - even usually reliable ones like Don Lynch - get this wrong.
It begs the question as to why there was still such a backlog on Sunday evening. Presumably because when it went down they might have still been in touch with Ireland, and on the Saturday and Sunday it was case of waiting until they came into contact with Cape Race? |
Closed: New threads not accepted on this page
US $474.60 1 Bid
