Seagoing Radio Equipment (years ago)

charles henry
9th August 2008, 16:42
Reading about marine equipment I am beginning to feel like the proverbial old man of the sea.

Am I the only one on this site that has sailed with and used the old Marconi TRF (380?) receiver with three valves plus another as a BFO. Plug in coils covering 100khz to 30 Mhz. Two tuning dials marked with 0 to 360 (?) usually covered with little pieces of paper stuck on bearing criptic writing such as GKG, 500, GPK, etc. No speaker just headphones. (See the 1940 photo on the Marconi Exhibition thread).

Then for sending there were two large wooden boxes one containing MF tx which was a single large "bottle" with wire leads covered with ceramic insulators. It also had the rectifiers. The HF box was also the same single tube both being a colpitts(?) oscillators directly coupled to the antenna. There was an MF/HF switch which simply changed the rectified DC to either of the boxes plus an antenna switching.

On the bulkhead there was a Xtal beat box which you could listen to when transmitting. As the ship rolled, the antenna swayed, the capacity varied as did the frequency. The tuning dial of both TX's were beautiful Muirhead drives and you sat sending with one hand with the other on the muirhead keeping the frequency nulled in your magic beat box.

Them were the days, am I the lonely methusalem or are there others out there?

de chas.(Pint)

BA204259
9th August 2008, 17:33
Chas

I once saw a cartoon, possibly in "Marconi Mariner" or similar publication, in which this very, very old R/O is saying to his first trip junior......"So I said to Marconi 'Why don't you invent radio and then I can go to sea and operate it for you?'".

I wonder where that idea came from?:) :) :) Not saying it was modelled on you, of course.... would I?

bert thompson
9th August 2008, 19:33
Welcome
Thought I was old but you beat me. My first was 11g D/F 381 TX Think 700 receiver with plug in coils and an animal in a cage which was a spark TX
Best wishes
Bert.

charles henry
9th August 2008, 20:16
(Pint) (Pint) Welcome
Thought I was old but you beat me. My first was 11g D/F 381 TX Think 700 receiver with plug in coils and an animal in a cage which was a spark TX
Best wishes
Bert.

That animal in a cage was a great thing, In a distress situation when the watches started (and 500 was blocked with, qrt distress, where distress, qrt idiot, etc) I switched on my little quench gap 50 watt emergency spark, put a book on the key, went into the chartroom, got a cuppa and when I came back, Five ton was quiet. For the rest of that period I stayed with the spark, boy, the sound of it, the smell of ozone, truly - great stuff.
de chas

K urgess
11th August 2008, 11:11
Aaah! The good old days.
Thank you Lord for making me miss them. [=P]

Roger Bentley
11th August 2008, 14:29
I think I have mentioned this before but here goes again. On joining my first ship the troopship Lancashre in September 1950, on entering the radio room I did not see any of the equipment I had trained on. No CR300 we had the 352A receiver for LF and MF, a type of Eddystone for HF reception. The 381 MF transmitter, the 376A HF transmitter, a quarter kilowatt spark Tx for emergency and the 579 DF. It all worked like a dream and I cannot remember any faults ocurring in two very happy trips on her. Oh Yes the radar was the good old 268. We did have a wire recorder for press but it was useless. Cheers, Roger

bert thompson
11th August 2008, 14:49
Forgot to mention Decca 159 Radar. This was on the Chelwood owned by France Fenwick. Understand that they ordered radars from Decca for all their fleet en masse. Would they have been the first company to have had radars on all their fleet ? Often wondered.
Bert

charles henry
11th August 2008, 15:57
I think I have mentioned this before but here goes again. On joining my first ship the troopship Lancashre in September 1950, on entering the radio room I did not see any of the equipment I had trained on. No CR300 we had the 352A receiver for LF and MF, a type of Eddystone for HF reception. The 381 MF transmitter, the 376A HF transmitter, a quarter kilowatt spark Tx for emergency and the 579 DF. It all worked like a dream and I cannot remember any faults ocurring in two very happy trips on her. Oh Yes the radar was the good old 268. We did have a wire recorder for press but it was useless. Cheers, Roger

Wire recorders, City of Paris, festive season, told by chief R/O to record the Queen's speech and not to forget under pain of keel hauling. Gave me a quick course and said, "if the wire breaks just tie a knot and it will keep going"
Came the magic time, reception good, started the recorder, "My loyal and faithfull objects...." the wire broke, I tied a know, and by the time I got the wire back through all the pullies the speech program was long over.

On a beer note, that lovely little Decca radar cost (By memory) 7,500 quid as opposed the 40 to 50k quid for the biggies "because you need at least 50 kw peak power otherwise its useless.......
Ah, the power of memories de chas(Pint)

Tai Pan
12th August 2008, 10:36
Fond memories of all that equipment. never faulty, nice hum from the rotary converters, yellow glow from the tubes, proper job.

charles henry
12th August 2008, 13:59
Fond memories of all that equipment. never faulty, nice hum from the rotary converters, yellow glow from the tubes, proper job.

Dont forget the starting handle of the rotary converters with the (I thought marvelous) no volt release protection....that should get the "youngsters" wondering
de chas(Pint)

Tai Pan
13th August 2008, 09:25
One problem was that these starting handles were usually placed on the right hand side of the knee hole in the desk. it was possible that having stated them up you could accidentally knock them off with your knee, and so you had to start again. youngsters wont know what we are talking about

R651400
13th August 2008, 11:04
Dont forget the starting handle of the rotary converters with the (I thought marvelous) no volt release protection....that should get the "youngsters" wondering.
The manually started rotary converters were museum pieces at Leith NC in '54 but we still had to learn about them. No volt release protection as it says was a small relay in the field coil circuit which held the starter handle fully on against a spring. If the ship lost mains the relay de-energised releasing the spring to return the starter handle back to the "start" or first contact position.. Glad I never had to sail with anything of this antiquity Chas.. Oceanspan Mk1 and after definitely for me.

charles henry
14th August 2008, 20:44
The manually started rotary converters were museum pieces at Leith NC in '54 but we still had to learn about them. No volt release protection as it says was a small relay in the field coil circuit which held the starter handle fully on against a spring. If the ship lost mains the relay de-energised releasing the spring to return the starter handle back to the "start" or first contact position.. Glad I never had to sail with anything of this antiquity Chas.. Oceanspan Mk1 and after definitely for me.

The ocean span (First edition) was the next thing to dying and gone to heaven - HOWEVER - having said that, The "antique" gear was a helluva lot more fun, when you actually sent a message you had really accomplished something. The other day thinking about the past (This site really gets one going) I suddenly remembered "voice" of Port Said, SUH which had a great warble, sounded like like a child going through puberty...de chas (Pint)

Ron Stringer
14th August 2008, 21:07
I suddenly remembered "voice" of Port Said, SUH which had a great warble, sounded like like a child going through puberty...de chas (Pint)

Was still the same last time I was there in 1966.

BobClay
14th August 2008, 21:56
when you actually sent a message you had really accomplished something.

I remember being on a Bank boat (Oceanspan/Atalanta) having trundled from Panama down to Kiwi (area scheme long gone) thankful that Bank Line, being old school, didn't talk to their ships much.

Off the Kiwi coast I got an SLT to send and hearing a faint signal from GKB on 8 Mhz, gave him a call more out of hope than anything else. Back he came straight away, took the SLT no problem leaving me feeling very chuffed.

Few minutes later the Russian Woodpecker started up and I realised how lucky I had been.

Tai Pan
15th August 2008, 10:59
OK. lets see who has a good memory. Those rotary converters powered the two tx,s. the MF had three windows, two small showed the mercury vapour rectifiers and the larger the onlly Valve, about 18 inches high and a large middle bulb. the other was the HF, only one window showing the only valve. Now, how did they work, not crystal contolled, must have been a VFO? and how did you link the two on HF, I cant for the life of me remember the knobs etc, the transmitting freq must have been very hit and miss especially on HF spare valves were carried in large wooden slated boxes, never had to change one. sailed on Isle of Jersey, Empire Medway and Esso Bedford with this set up, it worked, but how?.

Shipbuilder
15th August 2008, 13:19
Here is a blurred photograph of myself in the radio office of the good ship RICHMOND CASTLE (completed 1944) in 1965. It was my first Marconi ship & I did find everything a lot easier to handle than AEI equipment, especially the receivers that had a very good calibrateable scale. The radio eqipment never had a single fault during the whole voyage. The DF was an ancient piece of kit with 1930s direct heated triodes in it and to tune it in, the three tuning capacitors all had to be rotated the same amount (why not a three-gang type, I wondered). Quite happy on that ship despite discomfort, poor food & gloomy accommodation. Very nice run though.
Bob

R651400
15th August 2008, 13:22
OK. lets see who has a good memory. Those rotary converters powered the two tx,s. the MF had three windows, two small showed the mercury vapour rectifiers and the larger the onlly Valve, about 18 inches high and a large middle bulb. the other was the HF, only one window showing the only valve.

I think the set-up you're referring to is the MIMCO MW 381 transmitter with a single high powerd triode oscillator, the oscillatory circuit and wave change as part of the aerial circuit and as ChasD has confirmed drifted as the ship rolled.
Pre Oceanspan, for SW the single valve oscillator seemed the norm with the oscillatory circuit and band switching for the SW bands much the same as the 381.
SW frequency accuracy was achieved by heterodyning the transmitter output with a separate "high stability" crystal control unit.
Makes the Oceanspan and CR300 look a cakewalk...

Tai Pan
15th August 2008, 16:32
sounds about right, I remember that control unit, ususlly placed a long way from the tx. as you say oceanspan etc, kids stuff.

Roger Bentley
15th August 2008, 17:15
I don't believe the 381 was able to be used for HF, in the ships I was on with that Tx there was another very similar in appearance and about the same size which was the 376A and this was the HF Tx. It had various coils/inductance type along one side and if a diligent RO decided to polish them up then you had to retune the thing. Its bandwidth was immense and usually stations like GZP and others would pick out the best signal point for reception and reply to that! It worked but I wondered how at times.

R651400
16th August 2008, 08:40
I don't believe the 381 was able to be used for HF, in the ships I was on with that Tx there was another very similar in appearance and about the same size which was the 376A and this was the HF Tx.
See 18 above Roger, in the terminology of the time I did say the 381 was MW (medium wave) though I wasn't sure what the companion SW transmitter was.
It would appear that Mimco used this single triode technology in both MW and SW transmitters until the arrival of the Oceanspan MkI.
During the war Marconi and others built the Air Ministry's T1154 which was a conventional three stage transmitter, oscillator, modulator and pentode PA. Marine version T1154L.

Tai Pan
16th August 2008, 09:41
Quite correct Roger, but if my memory is correct, the MF tx had to fired up so that the rectifiers could be used on the HF tx. The bandwidth must have been very wide as freq selection was a bit hit and miss. none of this pretuned stuff with coloured knobs, needed about 4 pair of hands, but it worked. The spare valves were housed in wooden cases suspended in their own cradles which was attached to the case by springs so it did not bounce about. 4 of these just about filled your cabin. somebody must have a photo or info ref these two sets.

Tai Pan
16th August 2008, 09:52
On Shaw Savill web site there is a photo of the 381. 500watts CW and ICW, bet that sounded good. however the 376 is not the one I sailed with, it had one window in the middle, no photo of that. I like the silence from our usual supporters!.

K urgess
16th August 2008, 12:15
Somewhere I'm sure I have pictures of this gear but my library is in a chaotic state at the moment. (Chaos theory rules around here)
If I find the appropriate publication I'll post.
Unfortunately I no longer have a T1154 only the R1155 but I have a manual somewhere.
Cheers
Kris

R651400
16th August 2008, 12:52
but if my memory is correct, the MF tx had to fired up so that the rectifiers could be used on the HF tx. Does Mimco short wave tx 550 ring any bells?

R651400
16th August 2008, 13:25
On Shaw Savill web site there is a photo of the 381. 500watts CW and ICW, bet that sounded good.
ICW (interrupted carrier wave) was a very crude form of modulation by interrupting the main oscillator using a simple buzzer in the oscillator grid circuit. It must have sounded almost class B with a very broad bandwidth
More info here posting 202..

http://www.shipsnostalgia.com/showthread.php?p=207200&highlight=interrupted+carrier+wave#post207200

K urgess
16th August 2008, 16:46
It seems that Marconi were not keen on showing their old gear even in the house magazine or their publications like "Wireless at Sea" and "The Marconi Book of Wireless".
The first Marconi Mariner house magazine was issued for July-August 1947.
By this time the Oceanspan was in full production and appears to have been so for quite some time.
The attached picture shows Radio Officer P. B. McNab who has over 25 years experience and is from volume 1 number 4 of the Mariner. It's in an article called "The Radio Officer" by "QTC" that may be worth posting at a later date.
The earlier mention of windows in the equipment and the fact that there are two morse keys made me think it may be relevant.
I will keep searching but my other radio equipment books are dated 1913 and 1925 which, I guess, are even before you "old-timer's" experiences.[=P]

charles henry
16th August 2008, 18:06
ICW (interrupted carrier wave) was a very crude form of modulation by interrupting the main oscillator using a simple buzzer in the oscillator grid circuit. It must have sounded almost class B with a very broad bandwidth
More info here posting 202..

http://www.shipsnostalgia.com/showthread.php?p=207200&highlight=interrupted+carrier+wave#post207200

I rather think the option was CW/MCW where the standard modulation built in was (by memory) 400 hertz
de chas(Pint)

R651400
16th August 2008, 19:00
I rather think the option was CW/MCW where the standard modulation built in was (by memory) 400 hertz
de chas(Pint) ICW as opposed to MCW (modulated carrier wave) was an entirely different process.
A 400 c/s MCW note would sound like the equivalent of a hearty "jam-tart" the morning after a night out on Belhaven Best if you happen to be so lucky.
MCW frequencies were at the very least between 850 and 1000 c/s.

Ron Stringer
16th August 2008, 19:08
The MIMCo transmitters that I am familiar with (Oceanspan I through to Challenger, Oceanlink 800 and EMX) all used 1000 Herz as the nominal modulating tone for MCW.

R651400
17th August 2008, 08:10
The attached picture shows Radio Officer P. B. McNab who has over 25 years experience and is from volume 1 number 4 of the Mariner. It's in an article called "The Radio Officer" by "QTC" that may be worth posting at a later date. I think everyone will agree this is a truly nostalgic shot. SW 376 on the left MW 381 on the right. Earlier models were painted black so this must have been the last of the line. The valve inspection windows are clearly seen on the hinged panels which presumably opened for valve change. The triodes were housed in copper strip for cooling but cannot recall the type number.Two morse keys and a changeover switch also something new to us Oceanspan types. Phones look a good old pair of S G Brown.
Kris this is the sort of nostalgic marine radio shot that should be in it's on gallery section!!

Tai Pan
17th August 2008, 10:06
Some success. visit www.gordonmumford.com
It shows a radio room with a 381 and its ? HF tx plus the TRF rx. pity the photos of the 381 are side on, but thats the set up I remember.

K urgess
17th August 2008, 12:09
Glad I got that right. [=P]
I didn't recognise the gear so thought it must be somewhere around the right era.
As to the gallery. Patience, patience. The mills grind slowly.
Cheers
Kris

charles henry
17th August 2008, 15:18
ICW as opposed to MCW (modulated carrier wave) was an entirely different process.
A 400 c/s MCW note would sound like the equivalent of a hearty "jam-tart" the morning after a night out on Belhaven Best if you happen to be so lucky.
MCW frequencies were at the very least between 850 and 1000 c/s.

I think this thread has fallen into a common trap, it appears that many morse operators think they were using CW. CW is a Continuous Wave and can only carry information if modulated, AM/FM/SSB etc.

ICW was Interupted Continuous Wave., ie., MORSE. There was no Modulation on ICW, it was either ON or OFF.

de Chas(Pint)

R651400
18th August 2008, 05:22
ICW was Interupted Continuous Wave., ie., MORSE. There was no Modulation on ICW, it was either ON or OFF. I don't think it's the thread that has fallen into a common trap Chas. How did TRF receivers of the time mentioned in posting 32 resolve your interpretation of ICW? If you follow John's link through to here and click on the image.....

http://www.gordonmumford.com/radio-02.htm

Bottom left hand. There's a black label on the 376 section of the transmitter which when magnified I assure you says:-
Marconi International
Marine Communications Ltd
London
1.5kw CW/ICW Transmitter

Tai Pan
18th August 2008, 09:43
This thread is really getting the memory stirred. Both the txs frequency were set by the vernier conrol, not hard on MF but on HF somewhat harder, there was a crystal control check box fitted and you tuned the hf tx to beat with the crystal freq However as it was a type of VFO then tuning slightly off freq on the set calling freqs often got you through when all the oceanspans were fixed by crystal, thats radio operating. both were ICW which often brought a rebuff from the shore stations, but again got you through. whilst somewhat primative compared with the black box era, they worked and gave no trouble, actually when in full flight it was very impressive, all the windows lit up and meter needles wanging over and a good hum from the converters. proper job

Tai Pan
18th August 2008, 11:42
I think everyone will agree this is a truly nostalgic shot. SW 376 on the left MW 381 on the right. Earlier models were painted black so this must have been the last of the line. The valve inspection windows are clearly seen on the hinged panels which presumably opened for valve change. The triodes were housed in copper strip for cooling but cannot recall the type number.Two morse keys and a changeover switch also something new to us Oceanspan types. Phones look a good old pair of S G Brown.
Kris this is the sort of nostalgic marine radio shot that should be in it's on gallery section!!

Yes doors opened for replacement or fault finding. also useful for hiding a few packets of ciggys on returning to UK.

charles henry
18th August 2008, 16:24
[QUOTE=R651400;239782]I . How did TRF receivers of the time mentioned in posting 32 resolve your interpretation of ICW?

The marine TRF receivers were fitted with a BFO just like the modern ones, otherwise you could not receive the interupted blips (Morse) of CW.

I think the transmitter being batted around (and the one in the thumb nail picture) is the same one that I started this thread by describing. It is also shown in the 1940 series of pictures in my thread "Memory lane from byegone days " which also shows wireless cabins starting with 1910 onwards at ten year intervals.

It was not 1.5kw it was a doubtfull 100 watts; as both the MF and HF sections were comprised of a single triode valve operating as an oscillator you were lucky if you could load the meters to the 100 watt mark.
de chas(Pint)

charles henry
18th August 2008, 16:31
Incidentally my comments on CW and ICW are NOT MY INTERPRETATION,
the definition is in the Radio Officers Handbook circa 1947 which at that ime was a half hour oral exam
de chas

R651400
19th August 2008, 09:19
It was not 1.5kw it was a doubtfull 100 watts; as both the MF and HF sections were comprised of a single triode valve operating as an oscillator you were lucky if you could load the meters to the 100 watt mark.
Chas this is becoming a bit of a two horse race with only a one word input "error," Mimcoman posting 35, which you didn't pick up on! Not to mention possibly a few yawns from our R/O readership.
If the following doesn't convince you on ICW, I withdraw gracefully.
The Mimco 376, see attached, was 1.5 kw and the 381 was 0.5 kw.
ICW was generated by switching in and out the smoothing circuit of the 1500V HT line to the single triode ie 2kw rotary converter output at 500 c/s through a full wave rectifier gives 1000 c/s unsmoothed output.
This seems to be the ICW method prefered by Mimco and on ships I've sailed with also RCA and IMR .
Siemens used the buzzer method of generating ICW, see attached.
BFO's are generally associated with superheterodyne receivers. TRF receivers in my limited experience used reaction to receive CW.

charles henry
19th August 2008, 16:20
Chas this is becoming a bit of a two horse race with only a one word input "error," Mimcoman posting 35, which you didn't pick up on! Not to mention possibly a few yawns from our R/O readership.
If the following doesn't convince you on ICW, I withdraw gracefully.
The Mimco 376, see attached, was 1.5 kw and the 381 was 0.5 kw.
ICW was generated by switching in and out the smoothing circuit of the 1500V HT line to the single triode ie 2kw rotary converter output at 500 c/s through a full wave rectifier gives 1000 c/s unsmoothed output.
This seems to be the ICW method prefered by Mimco and on ships I've sailed with also RCA and IMR .
Siemens used the buzzer method of generating ICW, see attached.
BFO's are generally associated with superhet practice. TRF receivers in my limited experience used regeneration to receive CW.

Sorry 'bout that, we are talking about different transmitters... mine was in two wooden cabinets (See the 1940 wireless room picture of the Marconi Fiftieth aniversary exhibition on my earlier posted thread).
Mea culpa de chas

Mimcoman
19th August 2008, 17:13
Hi Guys:
Interesting thread, this. I can only remember ICW from college (along with spark gaps, quenching and rotary spark gaps) but never heard it at sea - as far as I know. (I have listened to the 17 kc/s Alexanderson signals from Sweden, though, and I was told that some form of spark-gap transmitter was used by our ex-Eastern Bloc radio colleagues to provide jamming signals.)

The "error" entry is not a reflection on Chas or anyone else - except me. I made an entry in the wrong thread and found I couldn't erase it but had to provide some sort of text. Next time (for there will surely be a next time...) I'll explain things better.

Roger Bentley
19th August 2008, 17:23
The interpretation of how ICW worked is correct, and I am awaiting final confirmation from an expert on early Marconi equipment. I seem to remember that listening to other ships using these earlier transmitters that they just sounded like MCW types. I think the term interuption really meant a form of modulation. I sailed with the larger Tx 386A which could be used for MF and LF. This was 1.5kW. On the 12 - 4 watch after leaving Colombo around 1800 bound for Fremantle I actually worked VIP on MF - it was a freak bit of propagation but it showed how these old transmitters could whack it out when conditions were right. A very interesting thread and I suspect there is more to come! Regards

R651400
19th August 2008, 18:48
I can only remember ICW from college (along with spark gaps, quenching and rotary spark gaps) but never heard it at sea

Mimcoman, you probably did! RCA and IMR were still using it in the 60's and it would sound just like any other form of standard MCW.
I think interrupting or keying any transmitter oscillator using a buzzer could be looked on as ICW.
Calling the modulation of the HT line of a transmitter as ICW I think is somewhat a misnomer.

K urgess
19th August 2008, 20:00
The attached pages are from the "Handbook of Technical Instruction for Wireless Telegraphists" by J. C. Hawkshead revised by H. M. Dowsett and published by Wireless World in 1925.
The last two pages are the interesting ones and confirm that ICW was amplitude modulated carrier wave.
Don't give yourselves headaches now. (?HUH)

K urgess
19th August 2008, 23:02
Having read this again it appears that ICW was a continuous radio frequency transmission with keyed audio "buzzer" or note.
I didn't realise that A2 or MCW could also be this type.
"Telegraphy by the on-off keying of an amplitude modulating audio frequency or audio frequencies or by the on-off keying of the modulated emission (special case: an unkeyed emission amplitude modulated) = A2"
(PMG Handbook)
The Oceanspan keyed the RF oscillator on and off with a bias resistor.

R651400
20th August 2008, 06:34
Looking at the circuit below, when keying, it appears the buzzer is producing bias pulses to the triode causing it to oscillate at the buzzer frequency. I think ICW for this type of configuration makes sense.
Switching out the HT smoothing circuit and running the triode directly from the full wave rectifier unsmoothed output I think comes closer to what we know as MCW or A2.
A2 or MCW in the Oceanspan was produced by modulating the PA with a 1000 c/s note from a two valve modulator, similarly the Reliance emergency transmitter although memory tells me it was a single valve 807 modulator.
In the Mk1 Oceanspan every stage including the modulator was keyed. MF oscillator keying slightly different from the HF oscillator.
This may have changed with later models when the Oceanspan became fully crystal controlled?

K urgess
20th August 2008, 11:14
Still not sure if I've got this right. (Whaaa)
As far as I can make out ICW was produced by transmitting RF continuously and keying the audio "tone" only to produce morse. Whereas the MCW that I'm familiar with keyed both the audio and the RF on and off.
Is that right or is it back to the drawing board? (?HUH)

Kris

Moulder
20th August 2008, 13:25
Still not sure if I've got this right. (Whaaa)
As far as I can make out ICW was produced by transmitting RF continuously and keying the audio "tone" only to produce morse. Whereas the MCW that I'm familiar with keyed both the audio and the RF on and off.
Is that right or is it back to the drawing board? (?HUH)

Kris

That looks about right Kris - infact could ICW be a kind of precursor to a sideband transmission? - the full RF carrier being a continuous transmission and data sent by keying a sidetone?

Steve.
(Thumb)

charles henry
20th August 2008, 15:46
Kris' posting was very interesting and that tranmitter had what we now call Amplitude modulation, at the receiving end you simply tune in the "carrier" and decipher the morse AM signal.
It appears that both sides of the "ICW" discussion were in effect correct because during the period of Kris' transmitter diagram it appears that the expression AMPLITUDE modulation was not used (invented) and they used INTERUPTED as they were in effect "interferin" with or "interupting" a CW signal.

I took my ticket at a much later date when the definitions as describled in the handbook had been changed and ICW was truly an "interrupted" signal.

Thanks for the information Kris, just looking at the coils used moves us back in time
de chas

R651400
20th August 2008, 16:23
Still not sure if I've got this right.
As far as I can make out ICW was produced by transmitting RF continuously and keying the audio "tone" only to produce morse.
In quotes above, Kris/Moulder do I understand you as saying in ICW mode there was a continuous CW RF output from the TX from switch on whether keyed or not?

K urgess
20th August 2008, 16:46
The biggest difficulty I have is with the idea of radio transmitters and receivers without any thermionic valves.
The 1913 handbook only mentions "Fleming valves" as rectifiers for possible use in power supplies or as detectors in receivers. Because it is so far outside my experience and learning, spark transmitters and receivers of this era are somewhat of a mystery although researching for answers to threads on SN has given me a very basic understanding.
The 1925 handbook describes the use of two electrode "Fleming" valves and the effect of introducing a third or control electrode between the two. It also describes their use as amplifiers and oscillators.
The main thrust though is still with spark technology and continuous wave technology being interesting but not commonly used and always developed so that it can be used in conjunction with spark technology.
This reminds me very much of 40 years later when the transistor was making it's appearance. I was taught valve technology because that was the most common equipment in use at sea.
Transistor technology was purely for entertainment purposes like portable radios. [=P]
The 1925 Handbook has the following passage relating to ICW
"Interrupted Continuous Wave Transmission (I.C.W.).-
If it is desired to employ C.W. transmission, but at the same time to affect receivers suitable for picking up spark signals, a buzzer may be employed in the grid circuit which is operated by the signal key and splits up the C.W. into a regular number of oscillation groups corresponding to the frequency of the buzzer vibrator."
This is not really amplitude modulation as described in my previous post.
In order to produce a reaction in spark receivers a series of damped RF pulses must be sent. If this RF train of pulses is sent at an audio frequency then a buzz will be heard similair to that produced by a spark.
C.W. transmissions would not be heard except for a click at the beginning of a pulse and one at the end because the signal is just rectified and smoothed. To enable spark receivers to decipher C.W. signals a "tikker" was introduced into the receiving aerial or detector circuit and this split up the C.W. at an audio frequency. A sort of primitive mechanical BFO. (EEK)
After describing a valve BFO and more complicated valve receivers and transmitters, the next chapter covers standard Marconi 1.5 K.W. set. Like going back to the dark ages.

K urgess
20th August 2008, 16:51
It would appear so from that previous description, R651400, but in this latest explanation is appears that it was originally a series of RF pulses sent at an audio frequency so that a morse character would be a buzz.
I now need to go and lie down in a darkened room to recover from too much stirring of the grey cells. (Whaaa)

Moulder
20th August 2008, 16:57
In quotes above, Kris/Moulder do I understand you as saying in ICW mode there was a continuous CW RF output from the TX from switch on whether keyed or not?


After reading post 52 from Marconi Sahib - no.

It appears that ICW was on/off keyed RF that was additionally modulated by a 'buzzer' circuit during the 'on' state.

Hows that?

Steve.
(Thumb)

(Move over Kris - and no farting). (Jester)

K urgess
20th August 2008, 17:14
It would appear that my first description covers the method used by that particular transmitter since it's primary use was telephony and would not have to be suitable for spark receivers. That one was AM.
I can supply waveforms if required but I must allow some cooling of the grey cells first. Get frostbite on my ears if I spend too long with my head in the fridge.

Kris
(My bed Steve, I'll lend you a gasmask [=P])

R651400
20th August 2008, 18:52
Kris/Moulder you got something going that the rest of us don't know about?

Back to ICW.... I've actually got four different versions of generating what was termed ICW but my suspicions are that equipment labelled as such got left behind after the convention following Cairo when modes moved to A1, A2, A3 and A3J colloquially CW, MCW and R/T and SSB.
If you can display any ICW waveforms Kris, it might throw some more light on the subject eg taking the earliest "clicking" ICW without any amplitude variance must have produced a signal close to the crudest form of FM.

K urgess
20th August 2008, 20:37
I'll try and scan some more but meanwhile....
You really have to forget about modulation of any sort with my latest and probably the first ICW system.
Put simply, a spark transmitter produced a damped oscillation as a capacitor discharged into a coil. The frequency transmitted depended on the resonant frequency of the circuit. If I've got it right the HT for the spark was produced by a motor alternator that produced ac at an audible frequency giving the buzz as the spark was maintained while the key was held down. So the spark was at audio frequency and every time the spark struck it charged up the capacitor and every time it dropped off the ac peak the spark would go out and the capacitor would discharge and charge in a decaying fashion through the coil at the resonant frequency of the circuit. So what you got was a series of decaying RF pulses at the frequency of the HT.
Eureka! I think I might actually understand how it worked at last. (EEK)
Please don't deflate me too quickly. Let me down gently if I'm wrong. (Whaaa)
When triode valves came along it became possible to produce a continuous wave but the HT had to be dc so there was no background "buzz".
To simulate a spark transmitter it was necessary to produce a decaying RF waveform. The valve oscillator was "poked" into oscillation by the "buzzer".
Let's say a morse dash is one second long and the transmitter basic frequency is 500 kc/s. If you have a 500c/s "buzzer" then a dash would consist of 500 pulses of continuous amplitude RF at a frequency of 500 kc/s. Each of the 500 pulses would consist of 1000 cycles of RF or as many as the circuit would "ring" as it decayed.
At this point my old lecturer Mr Redvers-Smith at Hull Tech would be dancing across the room in front of the class waving his arms and bobbing up and down to simulate waveforms. Sorry fellers you'll have to put up with my crappy typing. (K)
This would translate into a buzz in the headphones at the buzzer frequency.
With my first example I expect that they did use amplitude modulation because it was used for the telephone part of the circuit and anybody with a similair set could receive it. You will have noticed that for ICW operation the normal transmitting key was screwed down and the "buzzer" was keyed. So the unit could be used as a standard CW transmitter.
I also suspect that the mechanical BFOs were being fitted to spark receivers so that they could receive CW.
I spent my first trip using a "pounder" key with no sidetone and a DC Oceanspan motor alternator whispering next to my right ear. Morse can be sent and received without sidetone or BFOs with a bit of practice.
The other point is that I don't know about you but I tend to confuse CW and CW.
CW in the very early days was Continuous Wave whereas MCW was always Modulated CARRIER Wave as far as I can remember.
Transmitters when I was at sea transmitted RF only while the key was down and that RF was amplitude modulated.

I apologise now if you knew this already.

R651400
21st August 2008, 09:48
Don't think anyone can pick holes in above Kris excepting the well screwed morse key.
For the present I only have 1938 Admiralty Handbook on W/T Vol I, the mere opening of which hurts the head so severely my hand reaches for another glass of "Chateau Kamikaze."
Anyone with Vol II who has the courage to open the covers may possibly find ICW theory, practice and waveforms to add gris to this thread.

Roger Bentley
21st August 2008, 10:07
I have received the following from the ROA Guru on early Marconi Equipment Dr Ken Jones.
This is what he says: - ICW means quite specifically INTERRUPTED CONTINUOUS WAVE. It was intended originally to enable CW transmissions to affect receivers intended for picking up spark signals or without means of hearing a CW signal. I should think this applied to a lot of old pre Second World War marine receivers, unless thay were provided with reaction (retro action controls like the 352A). There were few receivers like superhets with BFOs.
A number of methosds can be used for interrupting CW such as buzzers and other electro-mechanical interruptors, sometimes involving a valve also. However, the method used in the 381 and 386A was to fit a doublepole double throw switch across the HT smoothing device. The latter consisted of a high capacity parellel capacitor followed by an iron cored choke (say 8 Henrys)and then aanother parallel capacitor. With the switch one way the smoothing unit was in series with the HT line. Switched the other way, the smoothing capacitors were shorted out.
The thing which made this method possible was the motor alternator run off the ships mains providing 100 or 200 volts at 500 cycles (hertz) for the primary of the HT transformer. Since rectification was bi phase using two MR1 (or MR4 in the 386) rectifier valves, without the HT smoothing this provided 1000 cycles imposed on the HT supply to the T250 (or MT14) oscillator valve. As a result the transmitted CW had a 1000 cycle superimposed note. A bit crude and not good audio as you will record but adequate for the purpose! Transmitters like the Oceanspan and Trader were a different kettle of fish. They had valve audio oscillators to modulate the 807s at a keyed audio frequency and the transmitted signal was modulated continuous wave.


End of quote. I realise much of this has already been laid out by previous posts but in view of Ken's kind response to my query I wanted to give his efforts due courtesy.

BA204259
21st August 2008, 10:29
Transmitters when I was at sea transmitted RF only while the key was down and that RF was amplitude modulated.



When you were on h/f and transmitting the required A1 signal (obviously only when key down), that RF was not modulated at all. It was pure CW (continuous wave). In effect, a carrier wave that happened to be carrying nothing, that is a pure continuous wave with no modulation. Hence the need for a BFO to "beat" with that signal and produce an audio tone that we could hear. The amplitude of every cycle was the same.

When you were transmitting on m/f, some ships, particularly some foreign flagged ones would also use A1. Most other ships would use A2, that is to say your CW was modulated by an a/f tone of (usually) 1,000 cycles. The amplitude of the carrier wave would vary "up and down" at the aforementioned 1,000 cycles per second (I think, though could be wrong here, to a depth of 95%), producing the classical wave form that we all know and love, it being second nature to us (EEK) and that was the tone we could hear. Not necessary to use a bfo to hear it, although of course we all did!

Very, very simple and easy to understand. (Isn't it?(Smoke) ).

No doubt somebody will inform me of the error of my ways, not for the first time!).

K urgess
21st August 2008, 11:38
Thanks to Roger and his guru Dr. Ken Jones for confirming the operation (Thumb) and to BA for reminding me to switch to CW before transmitting on HF. (EEK).
I found the most difficult thing was getting around terminology like "tikker", "jigger", "coherer", "decremeter", "interrupter", "syntonisation" and "cymometer". (Whaaa)

R651400
21st August 2008, 12:24
A bit crude and not good audio as you will record but adequate for the purpose!
The switching out of the TX HT smoothing circuit to modulate the MF transmitter was used well into the 60's.
RCA used it on their 5U console also IMR on a MF only transmitter, type number unknown, I sailed with in Glen Line,.
The Siemens SB502A W/T - R/T transmitter, a contemporary of the Oceanspan MK1, had HT provided by a DC to DC rotary transformer (48v to 700V DC) with uniquely a separate 700 c/s alternator for the purpose of providing modulation.
In the ICW switch position the 110V 700 c/s output from this alternator was applied direct to the microphone amplifier!

K urgess
21st August 2008, 13:04
Attached is the original of the publication I got the information from.
Some of it is very familiar.
When you think about it, as valves developed and more grids were added the Txs and Rxs got more and more complicated. It must have come as something of a culture shock to try and get the same quality out of transistors.
Almost a back ward step to these early days when the only valve available was a triode. (Whaaa)

Darkened rooms and comfortable reclining positions are available if your live in my area.(Night)

Cheers
Kris

Moulder
21st August 2008, 15:24
........ and to BA for reminding me to switch to CW before transmitting on HF. .......



and on MF working freqs? Wasn't A2 (MCW) a requirement on 500 KHz only? :sweat: (?HUH) (Whaaa)

Steve.
(Thumb)

K urgess
21st August 2008, 15:42
Here you go, Steve.
"Bands between 405 and 535 kHz
89. (1) Transmitters used in ship stations working in the authorised bands between 405 and 535 kHz must be provided with devices readily permitting a material reduction of power.
All ship stations equipped to work in the authorised bands between 405 and 535 kHz must be able to:
(a) send class A2 or A2H emissions and receive class A2 and A2H emissions with a carrier frequency of 500 kHz.
(b) send, in addition, class A1 and either A2 or A2H on at least two working frequencies;
(c) receive, in addition, class A1, A2 and A2H emissions on all other frequencies necessary for their service.
The provisions of (b) and (c) do not apply to apparatus provided solely for distress, urgency and safety purposes."
PMG Handbook, 1975 Edition.

Moulder
21st August 2008, 16:25
Here you go, Steve.
"Bands between 405 and 535 kHz
89. (1) Transmitters used in ship stations working in the authorised bands between 405 and 535 kHz must be provided with devices readily permitting a material reduction of power.
All ship stations equipped to work in the authorised bands between 405 and 535 kHz must be able to:
(a) send class A2 or A2H emissions and receive class A2 and A2H emissions with a carrier frequency of 500 kHz.
(b) send, in addition, class A1 and either A2 or A2H on at least two working frequencies;
(c) receive, in addition, class A1, A2 and A2H emissions on all other frequencies necessary for their service.
The provisions of (b) and (c) do not apply to apparatus provided solely for distress, urgency and safety purposes."
PMG Handbook, 1975 Edition.

Arigato.

(Thumb)

R651400
21st August 2008, 17:18
(a) send class A2 or A2H emissions and receive class A2 and A2H emissions with a carrier frequency of 500 kHz.

Circa 1956 A2 was MCW what is A2H?

K urgess
21st August 2008, 17:23
Circa 1956 A2 was MCW what is A2H?
Single sideband full carrier.
I've had my PMG handbook for 32 years and I've nearly worn it out in the last few days. [=P]

Kris

R651400
21st August 2008, 17:57
Single sideband full carrier.
I've had my PMG handbook for 32 years and I've nearly worn it out in the last few days. Well worth the effort Kris. There are one or maybe two senior R/O's on site that wondered how us youngsters managed!

Roger Bentley
21st August 2008, 19:35
It would seem those of us who went to sea post war until about 1952 encountered some very old equipment particularly in the companies that employed their own staff. Certainly the Lancashire and Cheshire in the Bibby Line had a mixture of old and fairly new. We did have a CR300 and CR100 on the Cheshire along with the 386A and 376A. Although the motor life boat still had a small spark Tx in it. Does anyone remember the MN100A that was fitted to enable BBC broadcasts to be received for the crew during the war, it was supposedly screened and gave adequate protection. We had one in the Lancashire. They were still happy days! Roger(A)

Tai Pan
22nd August 2008, 10:04
I must be the biggest duffer, I thought ICW was to get "Iced Cold Water" for the scotch.

charles henry
22nd August 2008, 14:27
I must be the biggest duffer, I thought ICW was to get "Iced Cold Water" for the scotch.

Good God, the very idea of diluting it, you must be a Sassenach
de chas(Pint)

Tai Pan
23rd August 2008, 10:06
OK chas. as the present Scottish prat in Nr 10 stole a large part of my pension, I have to drink blended during the week,, that needs cooling down a bit, however I never add h2o to Malt but thats only at weekends.

Roger Bentley
23rd August 2008, 20:02
Dr Ken Has asked me to make the following amendment to his previous details on these two transmittrers. The oscillator valve in the 386A was an MT6B not as previously stated an MT14 The MT14 was used in the more powerful 388. They both had a pair of MR4 rectifiers in bi-phase configuration, with the same radiated 1000 c.p.s. (Hertz) with ICW. Cheers, Roger

charles henry
24th August 2008, 13:57
OK chas. as the present Scottish prat in Nr 10 stole a large part of my pension, I have to drink blended during the week,, that needs cooling down a bit, however I never add h2o to Malt but thats only at weekends.

Once they get anglified they become useless. Even only on the weekends a pure malt must be an expensive habit in these over governd isles, regards chas

Baulkham Hills
5th September 2008, 13:29
Hi there,

In the PMG Handbook for Radio Officers 1961 edition, it lists
bands between 90 and 160 kc/s with a calling frequency of 143 kc/s A1,
I am interested when these frequencies were used and when they fell into disuse.
From memory WCC and WSL were licensed for this frequency and some U.S.A. flag ships were in List of Ship Stations as having this frequency.
(w denoted this frequency).
Would any of our senior colleagues have information about this.

Cheers

King Ratt
5th September 2008, 19:58
I believe the transatlantic liners were equipped with LF W/T. I went to sea in 1963 and I don't think I ever heard any ship shore traffic in that band while tuning around. There is no mention of it in my HandBook for Marine Radio Communication published in 1993. This publication being the equivalent of the old PMG Handbook.

K urgess
5th September 2008, 20:28
Not mentioned in the 1975 edition of the PMG Handbook (Blue cover) either.

Kris

Mimcoman
6th September 2008, 02:19
I seem to remember that GKA had blind traffic broadcasts in that band at one time, but may be mixing it up with the GRL broadcasts on 1.6MHz. Maybe one of the GKA hands can correct me?

Baulkham Hills
6th September 2008, 07:04
Hi there,

I am sure this band was used by the transatlantic liners probably pre-ww2,
and the American flag ships were war built.
Incidentally ships were advised to keep watch on 143 kc/s for 5 minutes hourly at H+35.
Portishead radio used to transmit blind traffic at Christmas on GKU 123 kc/s
from memory. So did Mauritius area station on a frequency in the same band.
The range was similar to 500 kHz during daytime and a lot less at night.
The admiralty book of wireless telegraphy circa 1930 (which I no longer have) went into considerable detail about the equipment for this and lower bands.
Maybe in 50 years time some one will be asking the same questions about 500kHz.

Cheers

charles henry
6th September 2008, 21:18
[QUOTE=Baulkham Hills;244317]Hi there,

In the PMG Handbook for Radio Officers 1961 edition, it lists
bands between 90 and 160 kc/s with a calling frequency of 143 kc/s A1,
I am interested when these frequencies were used and when they fell into disuse.

Having been responsible for an arctic TTY installation of a VLF sistem 500 miles apart and using frequencies of 139 and 125 khz. The antennae specified at both stations were identical. Although the 139 khz end tuned up nicely we had a lot of trouble at the 125 khz end and had to add a great deal of both couterpoise and wire in the air. at both ends we use identical ATU tuning coils which were of litz wire four foot in diameter and about 7 feet long.

I find it difficult to believe that any ship would be able to muster any sort of reasonably efficient antenna for these wavelengths
de chas(Pint)

Baulkham Hills
7th September 2008, 08:08
Hi there,

The aerials for l/f band would be a problem onboard a ship alright,

Anybody remember the Marconi Mark IV radar, I sailed with this in the early seventies on a 1953 built steamer (strictly w/t and no VHF). This had an oscilloscope built into the radar with many test points for fault finding.
In nine months onboard the only problem I had, was occasionally retuning it, which could be easily done with the oscilloscope and a stationary scanner.
Previously I had sailed with the Marconi Raymark or Raymarc and the test equipment was a pair of headphones and a capacitor to track the PRF.
I had plenty of problems with this one.
Another Marconi radar was the Hermes and its companion Argus, Tons of valves and not in any way reliable, but an excellent heat producer.
I recently sailed with Anchultz gyros and it comes with multi test points with can be accessed from a l.e.d. display. It seems things are turning full circle.

Cheers

R651400
7th September 2008, 19:00
The long wave band and it's calling frequency 143 kc/s had disappeared when I went to sea in '56. The transmitters were still used to broadcast the Area 1A traffic lists and other broadcasts on 129.55 kc/s call sign GKU.

BobClay
7th September 2008, 21:26
I sailed with the Marconi Mark IV on a Bank boat in 1970/71. In 13 months I never had much trouble with it. The transmitter/receiver unit was situated in a cupboard in the radio room, a big box about the size of a fridge freezer which meant I could work on it on watch and as described, the inbuilt test facilities were really good. (Bank Boats didn't exactly carry much in the way of spares/test equipment/tools... all was at bare minimum).

If I remember rightly the magnetron used a fixed magnet, a huge horseshoe that remained in position when you put in a new unit. But my memory may be playing tricks on me. I'd never seen one until I joined that ship (did my ticket on the Raymarc and a Decca 404). I thought it was a good bit of kit.

King Ratt
8th September 2008, 09:55
I did my radar ticket on Marconi Mark IV at Leith in 1963. When later, I joined my first ship RFA Cherryleaf, the radar was a Mark IV and it was on the blink. My boss had no radar ticket and was wary of doing any fault finding. I got it going after a while. That was a lucky good start to my seafaring career.

dwdb
11th September 2008, 10:02
[QUOTE=Baulkham Hills;244555]Hi there,

I am sure this band was used by the transatlantic liners probably pre-ww2,
and the American flag ships were war built.
Incidentally ships were advised to keep watch on 143 kc/s for 5 minutes hourly at H+35.
Portishead radio used to transmit blind traffic at Christmas on GKU 123 kc/s
from memory. So did Mauritius area station on a frequency in the same band.
The range was similar to 500 kHz during daytime and a lot less at night.
The admiralty book of wireless telegraphy circa 1930 (which I no longer have) went into considerable detail about the equipment for this and lower bands.
Maybe in 50 years time some one will be asking the same questions about 500kHz.

Cheers[/Q UOTE]

143 kHzwas alive and well up to the end of 50s I was on Queen Elizabeth for over four years in the the 1950s and we had a 3KW MW/LW transmitter which was used for traffic on 143 when MF was busy (or blocked by distress) Mainly used with WSL - At that time 143 was used by 'United and possibly 'America' more that us.
Originally there was a long wire aerial from foremast to aftermast but this was abandoned after a failure in the hoist dropped one of the 5ft insulators on to the passenger decks and we loaded both MF and LW on to the 'new' MF aerial which went from the top of the transmitter room to the aft funnel and then to the aft mast - full power could not be delivered due to arcing at the deck insulators so it was reduced to 1 KW on long wave. The transmitter was a coast station transmitter about 10' long, 7' high and 4' deep weighing about a ton and, like the three 1kW HF transmitters, was remote controlled from the Radio Room about 400' forward. Antenna tuning was normally only carried out once a year, during the 6 week drydock!!, and necessitated sitting inside the transmitter to adjust the taps on the 2' diameter tuning coil

When I joined QE she had 9 R/Os and one was responsible full time for the maintenance of all the radio room equipment (6 transmitters, 12 receivers, 2 phone terminal bays and 2 x 65kVA generators in the engine room) and one (on the 4 to 8 watch) did additional duty maintaining the bridge equipment of 3 radars, VHFs and MF R/T with DF, Loran and Decca. by the time left we were down to 6 R/Os - I did one or other of these duties for the entire time I was on the ship - the full time 'tech' was designated Staff Chief Radio Officer by IMR

andysk
11th September 2008, 11:43
[QUOTE=Baulkham Hills;244555] .... When I joined QE she had 9 R/Os and one was responsible full time for the maintenance of all the radio room equipment (6 transmitters, 12 receivers, 2 phone terminal bays and 2 x 65kVA generators in the engine room) and one (on the 4 to 8 watch) did additional duty maintaining the bridge equipment of 3 radars, VHFs and MF R/T with DF, Loran and Decca. by the time left we were down to 6 R/Os - I did one or other of these duties for the entire time I was on the ship - the full time 'tech' was designated Staff Chief Radio Officer by IMR .....

Hi DWDB

When I came ashore and joined IMR in 1978, there were at least two ex QE / QM R/O's, Bryan Staton and Mike Jeffery, maybe a some others as well but their's are the only names I can remember at this stage. Anybody know where they are now ?

omega2618
11th September 2008, 22:35
BobClay and his reference to the horseshoe shaped magnetron magnet reminded me of an incident on a particular vessel.
It was well known that there was always a very strong magnet available,recovered from a defunct magnetron, for general ships use.(Retrieving tools etc from bilges).On this occasion,however,the request to borrow the magnet came from the Purser.
' I've a crew member in the hospital who thinks he may have a large piece of metal lodged in his eye.Any chance of borrowing the magnet? If I pass it across his eye the piece of metal should jump out onto the magnet.' Having advised him that exit wounds were nearly always greater than entry wounds he left the Radio Room minus the magnet but with the clear vision of an eyeball firmly stuck to the pole piece.

Baulkham Hills
12th September 2008, 02:31
143 kHzwas alive and well up to the end of 50s I was on Queen Elizabeth for over four years in the the 1950s and we had a 3KW MW/LW transmitter which was used for traffic on 143 when MF was busy (or blocked by distress) Mainly used with WSL - At that time 143 was used by 'United and possibly 'America' more that us.
Originally there was a long wire aerial from foremast to aftermast but this was abandoned after a failure in the hoist dropped one of the 5ft insulators on to the passenger decks and we loaded both MF and LW on to the 'new' MF aerial which went from the top of the transmitter room to the aft funnel and then to the aft mast - full power could not be delivered due to arcing at the deck insulators so it was reduced to 1 KW on long wave. The transmitter was a coast station transmitter about 10' long, 7' high and 4' deep weighing about a ton and, like the three 1kW HF transmitters, was remote controlled from the Radio Room about 400' forward. Antenna tuning was normally only carried out once a year, during the 6 week drydock!!, and necessitated sitting inside the transmitter to adjust the taps on the 2' diameter tuning coil

When I joined QE she had 9 R/Os and one was responsible full time for the maintenance of all the radio room equipment (6 transmitters, 12 receivers, 2 phone terminal bays and 2 x 65kVA generators in the engine room) and one (on the 4 to 8 watch) did additional duty maintaining the bridge equipment of 3 radars, VHFs and MF R/T with DF, Loran and Decca. by the time left we were down to 6 R/Os - I did one or other of these duties for the entire time I was on the ship - the full time 'tech' was designated Staff Chief Radio Officer by IMR[/QUOTE]



Thanks for this information about the lf band, it filled in some gaps for me.

Cheers

Roger Bentley
13th September 2008, 14:48
I did post somewhere that the Cheshire when I was 3rd R/O on her in 1951 had a 386A Tx 1500 watts this had been put in the ship by the RN when she was an AMC and left there afterwards. I used it once when in the Med to call Portishead on 143 and he came back immediately and I cleared traffic on one of the working frequencies in the 120kcs range. Our main aerial only ran from the fore mast to the funnel but it seemed to load OK. Cheers - Just back from a cruise on the Ventura - sadly no radio office on her!

bert thompson
13th September 2008, 16:34
Yes the Raymarc was lovely to tune. Trouble on the ship I was on was that Singapore depot had no spare Klystrons. My first radar with Marconi was a Mk2 pre production and diagrams about the size of charts.
Happy days
Bert.

dwdb
14th November 2008, 06:51
Response to Charles Henry May 2008

Yes - I sailed with all that and a SPARK EMERGENCY TRANSMITTER on a tanker!! British Bombardier' in 1953