What broke down in the Marconi room?


Mar 22, 2003
6,086
1,401
383
Chicago, IL, USA
www.titanicology.com
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.
 
May 3, 2005
2,599
277
278
>>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 ?
 
Mar 22, 2003
6,086
1,401
383
Chicago, IL, USA
www.titanicology.com
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.
 
May 3, 2005
2,599
277
278
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
 
Mar 22, 2003
6,086
1,401
383
Chicago, IL, USA
www.titanicology.com
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.
 
Mar 3, 1998
2,745
76
0
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
 
Mar 22, 2003
6,086
1,401
383
Chicago, IL, USA
www.titanicology.com
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.
 
Mar 3, 1998
2,745
76
0
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
 
Mar 17, 2010
214
2
71
London
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
 
May 3, 2005
2,599
277
278
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
 
May 3, 2005
2,599
277
278
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.
 

Dan Waddell

Member
Mar 28, 2011
7
0
31
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
Mar 28, 2011
7
0
31
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?
 

DonJ

Member
Apr 17, 2012
16
1
31
The main reason for the backlog was that Phillips saved them for Sunday night, when he could contact shore stations directly. He seems to have cleared the few messages he had on hand in the hour after the radio was fixed.[/QUOTE]

It was a peculiarity of radio communications that signals were usually better at night.
The British army found this when using morse code signals from distant bases to UK; such as the SAS secreted on the Falklands just after the Argentinian invasion. Their equipment meant that they could prepare a long and detailed report, type it into the equipment then, when they were ready, press SEND and it was sent in about 1 second. Even a four A4 page report could be sent in less than 2 seconds - no where near enough for enemy wireless detectors.
 

DonJ

Member
Apr 17, 2012
16
1
31
If you're asking about Virginian's report of a signal ending abruptly, then I attribute that more to the AC falling below threshold, unable to generate the "pressure" (to use the 1912 term) needed for a spark to discharge across the air gaps between electrodes. In short, the DC power being supplied by the ship's dynamos was failing and could no longer run the alternator at the speed needed to generate useable AC.

If we remember Capt Rostron's attention to detail, he would have detailed a steward to stand beside Cottam: if he wanted a coffee he would get one, if he wanted a pee the steward would get him a bottle; all so that he did not have to leave the radio.
The last message that Cottam received was complete at 02.12 but the Virginian picked up a broken message at 02.17. Therefore, Cottom did not hear it and thus, Virginian was closer to Titanic. probably the other side of the ice field and thus, unable to assist.
 

DonJ

Member
Apr 17, 2012
16
1
31
was the last sent by Phillips as it matches what Bride said was done before they abandoned the wireless cabin.[/QUOTE]

There is one problem about accepting evidence from Bride since, while in America he gave 3 interviews and each one placed him in a different place as Titanic sank.
1) he claimed he was with Jack Phillips in the wireless room to the very last
2) He was reported to be helping to unship one of the Englehard boats
3) He was reported to be UNDERNEATH that same Englehard as the musicians played the last piece of music which he claimed was 'A Songe of Autumn'. How could he have heard it from underneath a boat.
Thus, much of his evidence must seem qurstionable.
 

Dave Gittins

Member
Apr 11, 2001
5,039
292
353
In a letter to the Marconi company dated 27 April, Bride said the trouble with the radio was on the night before the collision, in other words, Saturday, 13 April. This can be confirmed from the radio records in that valuable book Signals of Disaster. There's a gap in the messages sent on the Saturday night until not long before sunrise.

Like DonJ, I don't trust Bride very much, but this time his story is independently documented.
 
M

Mila

Guest
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?
"Skip" of radio signals happens when a super refraction is present. In this situation one could recieve signals from nearby stations and from far away stations, but could miss signals from the stations located in between. Of course lost signals by the end might have been due to the power getting lower, but I read that before the collision there was "skip" between the Titanic and Cape Race. Does somebody know anything about this "skip"?
 
Nov 14, 2005
1,539
638
248
Hi Mila. According to many articles I have read I have not heard that skip was a problem that night. Titanic was working Cape Race quite hard sending and receiving messages. We've all seen the famous quote "shut up, shut up I am busy. I am working Cape Race". It could have been an intermittent problem but I haven't come across it for that night. It was a problem with that type of radio at times. Many people believe that Titanic had the best radio equipment for her day but that's not true. There were already better systems/technology out there but because of patents and questionable practices by Marconi they weren't yet available for use by many. Here's a few links about what I'm talking about if your interested. I'm sure somebody like Parks Stephenson could tell you but I don't know if he comes here anymore.
Cape Race | Receiving Titanic
Radio and the Titanic

P.S. I poked around the board a little and did read where Olympic's radio operator that night did say he was having some problems with "atmospherics". Whether that was a skip problem or not I don't know.
 
Last edited:

Rob Lawes

Member
Jun 13, 2012
1,187
727
208
England
Titanic transmitted somewhere between 500 and 1000khz which is very much in the ground wave region when it comes to wave propagation. There would be a very shallow sky wave which would.be attenuated by the atmosphere far less at night due to the thinner ionosphere layers.

Ground wave transmissions over open water are effected by very little except the power of the transmitter and the size of the aerial.

Large Low Frequency transmitter aerials can be kilometres long to achieve global ranges.

The skip distance of a transmission is the distance between the transmitter and the first returning sky wave. By night because there is no sun to bombard the ionosphere the layers collapse into each other so that it is much thinner. High power, higher frequency transmissions are therefore not attenuated and become space waves. Lower power, lower frequency transmissions are still attenuated but the skip distance is increased.

There is an area called the silent zone which is the distance between the first returning sky wave and the end of the ground wave. This zone can vary in size.

One final thing that can rapidly change ranges is the e-layer of the ionosphere. There is an effect known as sporadic E which is where clouds of charged particles are trapped in the e-layer at night and provide a temporary boost or shortening of sky wave attenuation depending on the frequency being worked and could last minutes or hours depending on the size of the cloud.

The only atmospheric conditions that principally effect ground wave ranges are weather based such as severe rain or thunder storms.

Ground wave ranges on the night the Titanic sank should have been as good as they could have been given the known weather.

Hope that helps.
 
  • Like
Reactions: 1 user

Similar threads

Similar threads