Ocean Span - negative resistance oscillator

charles henry
12th June 2008, 15:56
Funny how all this nostalgia brings up things that you never considered before.
I sat my ticket on and sailed with the original ocean span and never gave it a thought but now this questions is beginning to bug me.

The MF portion of the ocean span used a NEGATIVE RESISTANCE oscillator,
(By memory it was called a transitron) as the grid current went positive the anode current reduced and visa versa.

With all the various types of tried and true oscillator circuits available why did they decide on this odd-ball type? Anyone out there know?
de chas henry (Pint)

Bruce Carson
12th June 2008, 16:34
"Negative Resistance Oscillator" would describe my ex when she got up in the morning:sweat:

mikeg
12th June 2008, 17:08
Knowing Marconi, it's probably the most cost-effective option i.e. low component count plus reasonable stability.

Bring on the flames (Cloud)

Mike

K urgess
12th June 2008, 19:25
Must have been an early Oceanspan, Chas.
All the ones I knew had Pierce oscillators for both MF and HF oscillators. The crystals for MF being half radiated frequency and 500 being LC in case of crystal failure.
Transitron (Miller) oscillators were mostly used for sawtooth waveform production as in radar/TV timebases etc.
Cheers
Kris
(Thankyou Danielson and Mayoh :sweat: )

Ron Stringer
13th June 2008, 07:25
On the Oceanspan I you had a rotary control that was coupled to a slug in a coil and also to a 4-digit counter. On the tuning chart was a 4-digit number against each MF working frequency (410, 425, 454, etc.) and to change frequency you wound away at the rotary control to reach the listed number. To get from 500 to 425 was frantic and the coast station occasionally lost patience and was calling you on their working frequency before you came up on 425.

Sister Eleff
13th June 2008, 07:40
"Negative Resistance Oscillator" would describe my ex when she got up in the morning:sweat:

Tut! Tut, Bruce. Very ungallant of you (Jester)

athinai
13th June 2008, 07:47
Ron Good Morning to you & Chas.
I sailed with an ''Oceanspan'' which had a ''Windie Windie'' for MF frequency Selection, sounds like the one described. it was not Desk mounted but a full length type., dont remember having any difficulty with it, but that was 45 years ago, I presumed that the Windie Windie was for LC frequency tuning? instead of Crystals ?

R651400
13th June 2008, 08:40
The MKI Oceanspan's MF oscillator uniqueness was in the slug tuning. Instead of dust iron it was copper, changing the value of inductance using eddy currents.
The second row three position blue knob in the attachment shows the MF frequency change.
Position three was a fixed LC 500 kcs position for calling. Positions 1&2 were working frequencies tuned by the lower right blue knob set to the incremental counter reading, not looking too happy in the picture.

charles henry
13th June 2008, 18:01
Yes it was probably one of the very first but worked well and gave no trouble.

I think the designer was just having fun - there is a lot of that in design work.

Am deeply impressed by the technical expertise available on this thread. Thank God we are all retired, de chas (Pint)

R651400
13th June 2008, 18:50
Thank God we are all retired.
Chas..If you gave me the chance to send my first TR from Laomedon/GPVP using a MKI Oceanspan and retiral, I know what I would choose!
Mark I Oceanspan? I doubt, particularly on MF, there was a better 100w marine transmitter ever built. IMR, Siemens, Redifon including foreign were in a different league.

mikeg
14th June 2008, 00:33
Am deeply impressed by the technical expertise available on this thread. Thank God we are all retired, de chas (Pint)

I'm amazed at the long Oceanspan technical memories you folks now have. I knew the transmitter very well technically whilst doing my PMG ticket and during my early days at sea but later on, with Shell in particular, the Oceanspan was usually relegated to the position of reserve transmitter (as you can also see to the LHS of my avatar). I always considered it fortunate to have a backup HF facility deep sea but nostalgia aside it just couldn't compete with the more modern higher powered transmitters. However it did always look 'impressive' and a reminder in looks of the early airborne units but I'm not sure operator ergonomics was that well thought out.

R651400
14th June 2008, 07:16
Oceanspan as a standby transmitter? A far cry from Oceanspan, CR300 receiver and Type M auto alarm as the entire ship's installation!
The area scheme when in full swing hardly necessitated anything over 100W.
I mention the MKI version Oceanspan because every stage was keyed making for a very punchy signal on MF. This changed somewhat when later versions were all crystal controlled.
I've related somewhere else on SN when on my last ship hearing a Glen boat maybe Glenroy/GPPN calling Shanghai/XSG when I was mid Pacific. I fired up my Swedish 400W transmitter and called him drawing a blank.

K urgess
14th June 2008, 11:21
If I close my eyes I can still reach out and feel the click stops!

mikeg
14th June 2008, 11:38
If I close my eyes I can still reach out and feel the click stops!

Kris, you could always take up safe cracking (==D)

I know exactly how you feel. Those cleverly designed click stops certainly helped out with speedy band & frequency changes.
One bit of nostalgia for me from the oceanspans are the 807's, not only for RF and mod duties but they can also sound wonderful used in a home built AF power amplifier (for those of you who are into retro hifi)
(Smoke)

K urgess
14th June 2008, 11:50
I thought I was just being a "sad old git", Mike. (Sad)

I would've thought that would have been more akin to a central heating system than an audio amplifier. [=P]
Did you use the stabilovolt as well? (?HUH)
Cheers
Kris

mikeg
14th June 2008, 12:34
I thought I was just being a "sad old git", Mike. (Sad)

I would've thought that would have been more akin to a central heating system than an audio amplifier. [=P]
Did you use the stabilovolt as well? (?HUH)
Cheers
Kris

Listening mainly done in the winter months - too hot in summer. Have used neon stabs (valve) but not in the 807 amps. Certain designs of Pi filters seem to have gone by the board, the high cost of copper a large choke can be prohibitive nowadays
:sweat:

charles henry
14th June 2008, 14:54
[QUOTE=R651400;223771]Oceanspan as a standby transmitter? A far cry from Oceanspan, CR300 receiver and Type M auto alarm as the entire ship's installation!
The area scheme when in full swing hardly necessitated anything over 100W.

I never sailed with a better layout and was lucky insomuch as I only had to put up with the lodestone df once, dont remember its name but the best DF I ever worked with had a sloping front with a small goniometer dial and if I remember correctly the tubes - whoops, valves had 1.5 volt heaters - whoops filaments.

Regarding transmitter powers if you look at it in the form of db's it gets into a better perspective.

regards to all de chas (Pint)

mikeg
14th June 2008, 15:18
[QUOTE=R651400;223771]Oceanspan as a standby transmitter? A far cry from Oceanspan, CR300 receiver and Type M auto alarm as the entire ship's installation!
The area scheme when in full swing hardly necessitated anything over 100W.

I never sailed with a better layout and was lucky insomuch as I only had to put up with the lodestone df once, dont remember its name but the best DF I ever worked with had a sloping front with a small goniometer dial and if I remember correctly the tubes - whoops, valves had 1.5 volt heaters - whoops filaments.

Regarding transmitter powers if you look at it in the form of db's it gets into a better perspective.

regards to all de chas (Pint)

It's okay Chas you can say plate for anode, tube for valve, heaters for filament - we all know what you mean.
Agreed re tx powers, a much better perspective expressing in db's however just comparing the two in HF QSO's the Conqueror's 1.6kW (if I remember right), certainly had some punch.

R651400
14th June 2008, 16:19
I never sailed with a better layout and was lucky insomuch as I only had to put up with the lodestone df once, dont remember its name but the best DF I ever worked with had a sloping front with a small goniometer dial and if I remember correctly the tubes - whoops, valves had 1.5 volt heaters - whoops filaments.

Mimco's DF that preceded the Lodestone was the MDF 579 with the goniometer separate from the receiver or it could have been Canadian Mimco's MDF 5 which was in a sloping case with a very small central gonio.
The 579 was my first ship's, Melampus/GMBZ, only radio nav throughout it's entire incident free life 1923-1957. By today's standards mind boggling.

charles henry
14th June 2008, 19:08
[Agreed re tx powers, a much better perspective expressing in db's however just comparing the two in HF QSO's the Conqueror's 1.6kW (if I remember right), certainly had some punch.[/QUOTE]

Yes indeed guess compared to 100 watts 1.6kw would be in the order of
13 db better or so. A major improvement but in all honesty with the great choice of HF area stations for free QSP I personally never found any problem clearing traffic with 100 watts. de chas (Pint)

Tai Pan
15th June 2008, 09:57
Very familiar set up.R/Os were R/Os in those days, no mamby pandy kilowatts.
Two rotary converts about ear height, battery charging elemnts in the base, very good in the tropics, (no air con in those days).

Moulder
15th June 2008, 10:46
[Agreed re tx powers, a much better perspective expressing in db's however just comparing the two in HF QSO's the Conqueror's 1.6kW (if I remember right), certainly had some punch.

Yes indeed guess compared to 100 watts 1.6kw would be in the order of
13 db better or so. A major improvement but in all honesty with the great choice of HF area stations for free QSP I personally never found any problem clearing traffic with 100 watts. de chas (Pint)

I'm digging deep into the memory banks - but, wasn't the Conqueror capable of 1.8 kW ?

Steve.
(Thumb)

R651400
15th June 2008, 11:00
Very familiar set up.R/Os were R/Os in those days, no mamby pandy kilowatts.Two rotary converts about ear height, battery charging elemnts in the base, very good in the tropics, (no air con in those days). MRGC and MED were a progression from PMG as was shipboard power supplies from 110V DC to 220V A/C. The syllabus for the first section of PMG 1 based on electrical theory with a heavy accent on electro magnetism, dc generators, rotary converters and rotary transformsers was probably one of the hardest exams ever.
PMG1 students when I took my PMG2 were held in awe by us lesser mortals.

mikeg
15th June 2008, 11:56
I'm digging deep into the memory banks - but, wasn't the Conqueror capable of 1.8 kW ?

Steve.
(Thumb)

Hi Steve,

Your probably right at 1.8 kW, my memory cells are a few db down. I enjoyed the power of that transmitter, far less frustrating as on HF generally answered first or maybe second call (Thumb)
Nothing worse than not getting through on your last watch and having to get msgs late at night - expecting the orders and it's turned out to be 'Happy Bithday Jim'.... I know, I know they're both equally important..especially to Jim(==D)

andysk
18th June 2008, 06:53
MRGC and MED were a progression from PMG ...... The syllabus for the first section of PMG 1 ....... was probably one of the hardest exams ever. PMG1 students when I took my PMG2 were held in awe by us lesser mortals.

Was PMG1 a different exam from PMG2, or the same one with a higher pass mark (I seem to recall 75% instead of 55 or 60% for the PMG2)

I think the awe in which PMG1 guys were held was due to their capability of morse at 25+ wpm, when us PMG2 students were struggling to get to 20 !

R651400
18th June 2008, 06:56
PMG 1 had two sections, part one electricity/magnetism and part two radio theory.
PMG 2 had one section incorporating a bit of both.

athinai
18th June 2008, 10:53
I was onboard a Greek Vsl named ''Angelus'' around 1969 and she was Steel Hulled, with upper decks all of Wood., Fine looking Vessel, On top of the Monkey Island was a Wooden Shack, and Inside was the Origional Radio Room with Spark Transmitter and all the Works, which was a Show-piece. It was not in service as the Shipowners created another Radio room behind the Bridge with more up to date equipment. Regretfully I never even got to take a photograph her.,

trotterdotpom
18th June 2008, 11:52
PMG 1 had two sections, part one electricity/magnetism and part two radio theory.
PMG 2 had one section incorporating a bit of both.

I think you've got that the wrong way round R65. If you already had a 2nd Class, you didn't have to do the Part 1 (Electricity/Magnetism, etc).

Also pass mark was 60% for 2nd Class and 75% for 1st Class.

John T.

R651400
18th June 2008, 12:12
I think you've got that the wrong way round R65. If you already had a 2nd Class, you didn't have to do the Part 1 (Electricity/Magnetism, etc).

Guess I was quoting taking the exam for the first time John.
Were there actually "mekons" around who took the 1st Class PMG straight off the cuff?? I do remember one at Leith Nautical who tried and failed and ended up in the fire service.
Sailed through life with a PMG2 only so perhaps not the best qualified to answer the query.
I do remember with hardly a smidgin of trigonometry trying to work thru the labyrinth of ac theory and teaching myself the rudiments of logarithms from an excellent wartime publication issued to the RAF. "Teach yourself mathematics."
Wish I had it now to exercise the remaining grey matter not already pickled by "Chateau Kamikaze."

K urgess
18th June 2008, 14:19
Trying to excercise the grey cells and having a bit of difficulty which is nothing unusual.
I did my PMG2 at Hull Tech College at the end of Queens Gardens in the shadow of Willie Wilbeforce.
I seem to remember that I had a two year further education grant and after that I was on my own.
We did the whole exam and most of passed the morse and practical quite easily. We had a maximum of three goes at the theory exam before being knocked back to having to take the other part again. Or getting thrown out. I think the decision to allow you to do the PMG1 was based mostly on your morse speed and your exam results.
The first go was usually before you'd even learnt it all and you stood a better chance at the second go. The third go was desperation time. One had to forego all the nurses and surrounding pubs in favour of doing some studying at last.
Sandwiched in between was the BOT Radar Maintenance course of (I think) 3 months (autumn term). It was usually done after the first year. That was really a doddle because most of the marks came from the practical section. This has always been something I was good at whereas the theory was an evil necessity. The drawback was that it was on the 5th or 6th floor of the college and the same floor was shared with the nurses. A poor arrangement when one is trying to concentrate on the internal macninations of a mark 4 or Hermes radar.
I think most of us PMG2s found that our natural morse speed was around the 20 mark. I know I could never push my speed up to 25s with any confidence.
One of the drawbacks is when most of your drinking buddies are trawler operators doing Specials. They tended to be a bit of a wild bunch and being easily led astray I was relieved to get what I did before the axe fell and I had to get a "real" job.
Looking back I'm glad I went to sea with a PMG2 and radar. Apart from preferring the black ticket it meant that I didn't get sent to the passenger boats. Although some of the stories paint a picture of endless debauchery I think it would have been the death of me.
I even declined the offer of MRGC from Marconi. They paid lip service to allowing you the required study leave. Probably the only reason I was selected to do the MED.
Going back to the subject of the thread we had Oceanspan VIIs at college and Atalantas so I never had to endure the I's tuning system or learn how the oscillator worked.
I remember when they cleared out a load of old equipment. I ended up with most of the gubbins from a US Navy AN-1 (?) radar. Nice black crackle finished cases and lovely brass nameplates. I think my parents dumped most of it when they moved house while I was at sea.
Unfortunately all the old Marconi gear was usually retrieved by them when no longer required.

Kris

athinai
19th June 2008, 11:41
I remember being exempt from the Technical Electricity paper when sitting the PMG1 as I held a 2nd Class. Just sat the Radio Paper which was not exactly Higher Science. Maybe we had to get a Higher Score in the latter., ? I cant remember exactly, In any case I never got any reward for having it,. The Job we did was exactly the same whether you Held a ''Special'' or ''2nd or 1st Class. Did companies pay an appreciable higher increase for having the 1st Class ?

Regards/

R651400
19th June 2008, 12:08
The Job we did was exactly the same whether you Held a ''Special'' or ''2nd or 1st Class. Did companies pay an appreciable higher increase for having the 1st Class ? /

Excepting the uniqueness of the morse code, don't think the job on "Arctic Corsair" and "Caronia" can be appreciably considered as being the same?

K urgess
19th June 2008, 12:41
I've got a bad case of the clutters but after an expedition into the depths of several archive boxes I found a couple of bibles.
The only vessel you needed a PMG1 or MRGC for was a Class I (PMG Handbook) or Class A (NMB Agreements). Those were "Ships carrying 200 passengers or more which are engaged in trading foreign or to Northern Ireland, Isle of Man and the Channel Islands." (NMB 1975)
NMB pay rates effective from 1st June 1975 for Radio Officers
From joining up to 3 years service pay was the same for all grades and all classes of vessel at a start of 191.40 per month increasing to 209.40 at the end of two years.
From 3 years upwards class A vessels up to 16,000grt for 1st, 2nd or 3rd R/O 241.20 pm
From 3 years upwards class A vessels over 16,000grt for 1st, 2nd or 3rd R/O 258.90 pm
From 3 years upwards class A vessels of any size 4th R/O 223.65 pm
From 3 years upwards class B for any R/O 223.65 pm
Plus in charge pay of 24.15 pm for class A under 16,000grt and 29.55 pm over 16,000grt. For Class B vessels it was 8.10 pm when more than one R/O was carried.
Maximum pay for a Class A over 16,00grt vessel was 363.00 pm after 21 years and 325.20 pm for Class B vessels.
All these were minimum wages so company salaries could be considerably higher.

Since I started on 45 pm in 1966 it seems that there was a 4 fold increase in salary over 9 years (EEK)

Cheers
Kris

M29
19th June 2008, 13:51
Was PMG1 a different exam from PMG2, or the same one with a higher pass mark (I seem to recall 75% instead of 55 or 60% for the PMG2)

I think the awe in which PMG1 guys were held was due to their capability of morse at 25+ wpm, when us PMG2 students were struggling to get to 20 !

PMG 2 had the Tech Elec Exam and Radio Exams, both at 60% if memory serves. You had a choice of 6 out of 8 questions but I think 2 were compulsory.

PMG 1 had passmarks of 75% but still with a choice of 6 out of 8 and 2 compusory.

If you took your PMG1 within 1 year of PMG2, you did not have to retake the Tech Elec paper.

Apart from that you had the SOLAS papers, the commercial working test, the faultfinding and radio direction finding test and of course the morse tests with the higher speeds for PMG1.

Alan

charles henry
19th June 2008, 14:17
Was PMG1 a different exam from PMG2, or the same one with a higher pass mark (I seem to recall 75% instead of 55 or 60% for the PMG2)

I think the awe in which PMG1 guys were held was due to their capability of morse at 25+ wpm, when us PMG2 students were struggling to get to 20 !

You are correct about the 25 wpm but the theory was also heavy, I remember writing three pages on the Bellini Tosi DF method. A year previous I had failed the PMG2 but decided to go for the first. The authorities said no way but eventually agreed pointing out that I would require six months before I could be in charge of a vessel requiring a first......... Turned out they had just "revised" the standards from the old "Draw a diagram of the 381 TRF receiver///" I949 certificate number 121. de chas (Pint)

Jeffers
19th June 2008, 15:48
Since I started on 45 pm in 1966 it seems that there was a 4 fold increase in salary over 9 years (EEK)

Cheers
Kris

It sounds good until you remember the rampant inflation in the '70s. I read recently that it was nearly 27% at one point. I must admit that, having lived through it, I don't remember it causing too much hardship at the time. That was before the days I had a mortgage of course, as with interest rates being as high as 15% to try and get inflation down it wouldn't have been a good time to be in debt!

K urgess
19th June 2008, 16:42
You can add to that, Jeff, that I decided to quit in 1977 and came ashore for the really low average wage of the time.
We also bought our first house and got a mortgage.
To feed the endless rise in interest rates all my policies and MNOPF had to go into the pot.
Just shows that once you decide that the anchor needs to be swallowed nothing will put you off.

Cheers
Kris

andysk
19th June 2008, 17:12
Similar for me Kris, I came ashore into IMRC in late 1978, bought a house, met my wife, took big cut in salary, which was OK for a little while, till about 1980/81 when inflation took off and interest rates went through the roof. But my eternal thanks are due to the then HQ Service Manager, Tom Corbett, (seconded from the IMRC Tilbury depot) in the early 1980's who negotiated a very reasonable pay rise for me and the service department, which meant that my MNOPF is still intact. A great guy, excellent boss and real gentleman; he retired to Mylor (near Falmouth). Christmas cards stopped a few years ago, so I presume he has gone to that great service depot in the sky by now.

You say nothing will put you off when swallowing the anchor, but by then there was really no option but to suffer and hope it all would get better. Maybe it has, maybe it hasn't, who knows.

K urgess
19th June 2008, 17:17
I forgot to mention my daughter born in 1978.
Talk about loading the dice. [=P]
By the early 1980s I was in computers, had sold the first house for double what we paid for it and moved into the country into a 4 bedroomed detached house in three quarters of an acre in land.
Can't have been all bad. Must've been the boom in computers and being in the right place at the right time.
Still couldn't get back the MNOPF though. (Sad)

BobClay
19th June 2008, 20:06
I got a PMG 2 in 1969 and remember doing the MRGC in 75. Didn't need to do the morse requirement for the MRGC (which stuck to 20wpm if I remember correctly), but the theory and practical had definately moved ahead from the PMG days.
When I joined GCHQ they made a big deal of pushing up the morse speed, (although I still think earwiggers don't have the same skills as operators), the irony then being I got sent to a satellite station, and never heard a morse note again. Words per minute can't really compete with kilobits per second... (to say nothing of megabits per second).
I still got the morsekey though, the old ETM4C electronic paddle key. Sits on a shelf next to an old SLR camera .... don't know which is more out of date.
:-D

Moulder
20th June 2008, 12:57
..................
When I joined GCHQ they made a big deal of pushing up the morse speed, (although I still think earwiggers don't have the same skills as operators),...............
:-D

Hi Bob,

Can't agree with you there - earwiggers haven't got the luxury of tapping the key to interrupt and request a repeat - they've just got to stick with it.

However, an earwigger who was an operator had all the skills needed and more.

Regards,

Steve.
(Thumb)

BobClay
20th June 2008, 20:16
Well it's a matter of opinion. Most of the ex-services earwiggers I trained with had a lot of difficulty with a morse key, other than those trained as operators, they didn't have much direct comms experience. And as for interrupting, one of their primary pieces of equipment was a large and good quality tape recorder. Not something I ever saw at sea.

I'm pretty sure if I'd dropped them in the pacific, trying to work Portishead's old pacific scan system (QSA1/2) with an Atalanta and Oceanspan setup, and a bit of wire for aerials, they'd have thought I was joking.

But...different strokes for different folks.

Mimcoman
20th June 2008, 21:12
Hi Steve,

Your probably right at 1.8 kW, my memory cells are a few db down. I enjoyed the power of that transmitter, far less frustrating as on HF generally answered first or maybe second call (Thumb)
Nothing worse than not getting through on your last watch and having to get msgs late at night - expecting the orders and it's turned out to be 'Happy Bithday Jim'.... I know, I know they're both equally important..especially to Jim(==D)
Hi Guys:
Re the Conqueror. As mentioned in another thread, self and Dave Woods took the first Conquerors to sea in mid 70s, with T&J Harrison's W-class bulkers. The first ones were - as you say - 1.8kW on the majority of the HF bands. But due, I believe, to Radio Regs requirements, the later ones were built to provide 1.5kW. I still have the handbooks I was given when Dave and I and MIke ??? were on a Conqueror course at Chelmsford.

In any case, I preferred the Crusader, PNP technology notwithstanding. It just seemed a more logical design -I felt I could faultfind most problems using the block diagrams. It certainly tuned the MF RT bands better (remember when they were called IF RT?). The only bad thing was the ledex drives -on two crusaders, I had to araldite the moter drive plates together when they worked loose and started slipping. I regularly checked them on every Crusader after that. Never had that problem on the Conqueror.

GKA used to say that they preferred the Commander/Commandant; one operator I knew when I was at coast stations said that it was possible to tell when a Commander was in use by the quality of the audio.

mikeg
20th June 2008, 22:31
Hi Guys,

I really wish I'd kept a record of all the courses I'd been on - many of the certificates/slips of paper have now been misplaced unfortunately. I'm almost certain I was on the Conqueror course at Chelmsford in the early to mid 70's. Because I was fortunate to stand-by five new Shell builds I attended very many manufacturers courses as the ships were then fitted with the latest radio and nav equipment.

I also had a love hate relationship with the Crusader but the experience of having to change the whole ledex/wafer assembly during an overnight port discharge coloured that relationship somewhat. (Remember that screwdriver slot to wiggle the shaft if you couldn't get any drive - so many of my earlier ships the wafers had been araldited or manipulated as a temporary repair).
Conquerors as I recall gave very few problems.
Happy Days,

ernhelenbarrett
21st June 2008, 06:26
GTZM must have been awash with cash in the sixties and seventies, in 1954 whenI got my PMG from Leith Nautical I started on the dizzy amount of 23
pounds per month and had to quote my paybook number (1744) to get it.
Also sailed with the Oceanspan 1 (that was modern compared to the 381 and Cr300, also had a spark set on the British Gratitude/MAGQ. They sent me to AST Hamble to practice on all types of TX's before joining my first ship, Avistone/GBSV for 6 months. Once they got me out on the Indian Coast for a few years with BI my pay was 100 rupees per month (7 pounds in those days} just as well the Gin was only 5 bob a bottle!!
Regards Ern Barrett

trotterdotpom
21st June 2008, 13:17
Was it Blue Riband, Ern? By coincidence I've just been talking about that. They still sell it and there is a website about it.

John T.

Baulkham Hills
15th July 2008, 21:42
Funny how all this nostalgia brings up things that you never considered before.
I sat my ticket on and sailed with the original ocean span and never gave it a thought but now this questions is beginning to bug me.

The MF portion of the ocean span used a NEGATIVE RESISTANCE oscillator,
(By memory it was called a transitron) as the grid current went positive the anode current reduced and visa versa.

With all the various types of tried and true oscillator circuits available why did they decide on this odd-ball type? Anyone out there know?
de chas henry (Pint)

I think the idea was, that this oscillator would produce a lot of harmonics and one oscillator circuit would cover 4,8,12,16 mhz with tuned circuits for the harmonics.
I remember using the Oceanspan just when the area system finished down in New Zealand, trying to send msg's to Uk and the States, really it was not up to it. I used to have some success about about 2am in the pacific, but it was very frustrating when the old man said the last sparky had no problems.
Before that the Oceanspan was ok, because messages were send blind by
Mauritius or Sydney Wellington and sub stations in Hongkong or India.
I sailed with the slightly bigger Globespan which was nothing special either.

Regards Michael

charles henry
19th July 2008, 17:00
[QUOTE=R651400;224741]Guess I was quoting taking the exam for the first time John.
Were there actually "mekons" around who took the 1st Class PMG straight off the cuff?? I do remember one at Leith Nautical who tried and failed and ended up in the fire service.


After the war I tried for a 2nd class but;-
I had forgotten how to study
I was busy with girls, hiking, girls, mountain climbing, girls, long distance cycling, girls to say nothing about boozing.

I failed the second.
Tried again but decided to sit a first as was brimming with knowledge have sat and passed City and Guilds, radio 1, 2,3 and telecomm 1,2,3 and four.

The PMG people said no way, you must have a second before it is allowed.
The owner of the college intervined and I was allowed to sit the first, got and absolute grilling. (The oral on the Radio Officers Handbook was an hour)
but I got it on the provision I couldnt use it until I had six months experience.
ie., could not be the chief on the BIG BOATS WHERE THEY CARRIED MORE THAN ONE.
73's de chas (Pint)

NoMoss
19th July 2008, 18:01
I was still struggling when I took my 1st Class PMG!