[Michael Oceanspan]

Andrew ,
The 1950's Radio room has been functional since last year and since the beginning of this year all Transmitter (Oceanspan) and receiver (Atalanta and Mercury) functions have been properly integrated to provide AM and full break-in CW. At present we can use 1.8, 3.5 MHZ easily, 5MHZ and & 7MHZ at a push. I frequently use it on VMARS' Saturday morning AM net on 3.615MHz. Last Saturday morning I was on with good AM contacts throughout the UK. (I am rubbish at CW)
We put in a good showing for Museums On the Air and also Marconi Day in April. (Oceanspan story do***ented in Practical Wireless April 2017 and April 2018)
In addition to the Rohde and Swartz 2100 that any visiting amateur can use, the 1950's radio room can also be used, but under supervision. (Not that many Amateurs are used to separate RX and TX, or tuning up large Valve transmitters!). If anyone does want to use the 1950s Radio Room, give me a PM or email via GB2MOP website and I'll try and be there to meet you. The only day I am committed to the Museum is Wednesday, we don't live far away and I'm often there on unpredictable days as well!!
The 1980s Radio Room from the "Pride of Calais" has working receivers, autokey and AutoAlarm. After a frustrating voyage of discovery the 1.5KW Challenger is within an ace of working (awaiting parts). See thread on Challenger on this forum - any info on Challenger or Station wiring would be gratefully received!

Best Wishes - Michael (GB2MOP/GW7BBY)

 

[Michael Oceanspan]

First of all Paul,

Glad you like the set up, the Oceanspan acquits itself very well. Now that its teething problems have been sorted out, mainly poor modulation, I get very good reports. I’ve been re-routing the antennas feeders via an antenna switch in anticipation of the Challenger coming on-line. As the feed from the Oceanspan is now in Coax, the length of the radiating component (Was inverted “L” direct to top of Oceanspan) is shortened, the antenna current has increased considerably. Still getting a good signal into Hack Green at 1530Hrs, be interesting to see how it goes earlier in the day.

I’ve attached a picture of the panel you mentioned. As you will see it is to select “Quick Heat” or Normal, Autokey or Manual Key. Our Oceanspan was a VIIE – an Oceanspan modified by Marconi as an Emergency transmitter when they found they had plenty of Oceanspans on hand in the early ‘60s and Oceanspans were being outclassed by more powerful SSB transmitters. I’ve reversed the modifications to revert it to Main Transmitter status. ( I don't know if existing Oceanspans were converted to VIIE, perhaps when a ship's equipment was upgraded?)

An Electra would be nice to go with the Mercury. However the Atalanta is a very nice receiver, but in need of realignment following replacement of nearly all its capacitors – a job for a quiet day with no visitors!

Now Andrew – well spotted! Yes DDS based vfo driven by Arduino (picture attached) opens the way to any Amateur band except that I can’t tune the Oceanspan driver stage higher than 7MHz. Problem is that 14MHz falls in the gap between 12 and 16MHz. The tuning slugs are underneath the transmitter unit, as soon as the transmitter is pulled forward off the Z contacts it can’t be powered so live working without some elaborate jiggery-pokery is ruled out. I might have another go at it during the winter shutdown: a) I can shift the vfo output to whatever multiple of 14MHZ the driver is expecting, b) it could be done “cold” with a signal generator or c) if I’m bored - some dangerous jiggery-pokery!

The unit below the VFO in the picture is a PSU to provide 650VDC for the Oceanspan and various HTs for the other equipment in the bay. Optionally you can have the Rotary converter running in the Oceanspan if you want the full R/O experience!

Sidetone? Now there’s a question, sidetone is present although I haven’t specifically wired it in and there is no obvious contact on the Oceanspan. Now you’ve made me think about it, I’m probably hearing it by virtue of the signal being strong enough to breakthrough the receiver on de-sense.

The Lodestone DF, probably works. I’ve not given it a lot of attention, but it is nice and clean inside. I’m thinking of feeding it with an Arduino generated nominal 500kHz signal with the ability to differentiate it between P & S, F & A antenna feeds. Of course if anyone’s got a Bellini-Tosi DF antenna kicking around……

Best Wishes - Michael (GB2MOP/GW7BBY)

 

[Michael Oceanspan]

Old Capacitors

Hi Paul,
All electrolytic and waxed paper capacitors become suspect after 40 or more years, more so if the equipment has been laid up unused for a long period. High value resistors generally tend to go high.

When it first arrived the Atalanta worked after a fashion, it would motor-boat (LF oscillation) if the RF gain was turned up too much; when a signal was tuned in it would be accompanied by a strong hetrodyne. There were other spurii to be heard as the tuning was changed.

There were a couple of burned out resistors and the RF gain control was faulty - that was tricky, it is a dual gang pot: one gang is Log, the other is anti-log.

After replacing the capacitors, and resistors mentioned above, it is greatly improved. The tuning is 500KHz out according to the dial in places and it has some quiet spots. It does some quite complex frequency changing so I'm looking forward to a day with Signal Generator and 'scope to sort it out.

The Mercury hardly worked at all when received by us, a couple of capacitors had actually exploded in it leaving shards of tin foil everywhere and it had a fair share of burnt out resistors. After replacing the all paper and electrolytic capacitors and re-alignment it is now a very nice receiver.

One more thing: I'd always believed mica capacitors to be reliable. However, the Mercury stopped working about two months ago, the fault was traced to lack of HT at the 1st Local Oscillator valve. The HT was fed from the HT rail by a 10K resistor (from memory) and bypassed to chassis by a 0.1 or 0.01uF mica capacitor. That capacitor had gone short and thus robbed the valve of its HT. So now I suspect all capacitors, though in fairness mica is still generally more reliable.

Incidentally, I do replace with modern components but photograph before and after so that all changes are do***ented. Originality is a subject often raised. You can get new/old stock TCC etc capacitors at a price but at over 30 years old are they any better than the ones you are removing? I know some people hollow out the old capacitors and fit modern ones inside. You have to weigh up how much originality means to you. The museum maintains a policy of keeping everything working - engines and radios. By fitting modern components such as capacitors and resistors where needed, the equipment can be kept in reliable safe working order without detracting from its appearance, feel and performance.

If your Atalanta is going deaf above 7MHz, can you get the front end valves checked or substitute known good ones before delving deeper?

Best Wishes - Michael.

 

[Michael Oceanspan]

Agreed, electrolytics are the least reliable of capacitors. As you say long idle periods make things worse.
I was intrigued by the clock you mentioned so had to "Google" it (In days gone by I might have had to spend hours in a technical library, or search catalogues to find it!) Congratulations it looks a very fine item; a fitting exhibit for any maritime radio room.
Michael

 

[Michael Oceanspan]

Ah yes, I should have realised! I am at a slight disadvantage having not come from a maritime career, but one thoroughly land-locked in Electronics, Radio and latterly software. When we retired to West Wales about 5 years ago, I became involved with the Radio collection at Internal Fire, since the focus of the collection is on maritime radio I have been on a fairly steep learning curve with regard to maritime procedures. As you see the learning continues!!
Thanks - Michael.

 

[Michael Oceanspan]

Sidetone etc

OK Andrew, I can see the sidetone input to the Atalanta as you describe, I can see how to derive the sidetone from the Oceanspan, but I don't see a specified terminal for it. I'll be at the Museum on Monday and will report back on my findings!
Yep, two 3 metre hoops at right angles, perhaps on a pedestal would be a Belini-Tosi DF Loop.
I understand that Marconi workshops and training colleges had Z rail extension rails or cables, I don't know if they were supplied to ships. Anyway we haven't got them and they would be dead useful!
I send you a circuit diagram of the Oceanspan Transmitter and Control Unit, probably tomorrow as I don't have the computer with all that data turned on and it's bedtime!
Michael.

 

[Michael Oceanspan]

NO, NO, boyo; you always tune for a dip!

Can I deduce from this quotation that you attended the Marconi College at Colwyn Bay?

Michael

 

[Michael Oceanspan]

I thought it might be bit of a stretch!! I seriously considered going to Colwyn Bay Wireless College in the mid-60s, but ended up serving an apprenticeship at Hawker Siddeley instead.
My usual day is Wednesday, in fact my wife is there too on Wednesdays. I'm usually there other days too. Opening hours are 10:30 to 5:00pm Wednesday to Sunday (Closed Mon and Tues). Best to drop me a PM on this site or send me an eMail via GB2MOP website and I'll try and be there to meet up with them. However, bear in mind that we will be away in France from 2nd to 22nd September. Perhaps a suggestion: October 12th and 13th are our big end of season "Crank-Up" days on both days we will have as many engines as possible running including the Proteus gas turbine. The Radio room will also, of course, be active. The museum is really buzzing on these days. Alternatively, for a more relaxed time, on 26th October we have a Museums at Night" event. This is a very pleasant evening fancy dress is optional we will be running engines: the proteus is even more spectacular at night. Again, the radio rooms will be active.
Plenty to think about!
Michael.

 

[Michael Oceanspan]

Sidetone etc.

Andrew,
Spent the day at the Museum today. Amongst other things, put the Oceanspan into CW mode. "Sidetone" is present in both Atalanta and Mercury. I have not specifically wired it that way as there is no sidetone output from the Oceanspan. The sidetone is present only by virtue of the local signal being sufficient to overcome the de-sense and is, of course, adjustable in frequency by the BFO. This is probably OK while working the same TX and RX frequencies. If operating cross channels you wouldn't hear yourself.
Aside from that had a good day with a handful of contacts around the country on 80 and 40 on the Oceranspan and then later switched over to the Rohde and Schwartz 2100 for some SSB contacts. Throw in a bit of useful tinkering, sunshine and a few visitors make sit a very pleasant day.
Michael.

 

[Michael Oceanspan]

Oceanspan Circuits.

Hi Andrew,
I promised you a copy of the Oceanspan circuits. Herewith, Transmitter and Control units.
Michael.
N.B. I couldn't see how to include these in a PM.

 

[Michael Oceanspan]

Hi Paul,

You'll have to be patient! my wife and I are in the middle of a three week holiday in France (courtesy of my sister who lives in France). We'll be landing back at Poole on 22nd, then onwards to wonderful West Wales!

Really, you've nothing to loose by fitting the EF85s and maybe something to gain. Do you have a signal generator? I won't get round to realigning ours until the Winter shutdown (November 2019 to Easter 2020). Before that the HT supply needs sorting out. You probably know that the Atalanta has 110V LT - heaters in series via a varistor to limit inrush current and 110V HT. Ours has been modified by a previous owner for 240VAC mains operation by fitting an autotransformer: the 110VAC tapping goes to the filaments and also to a full wave silicon bridge rectifier consequently the HT is closer to 150VDC than 110VDC. From a purely electrical point of view it probably does no harm as all the capacitors are rated for 250V and the resistors should stand the extra few milliamps. However, from an RF and AF point of view I'm not so sure. The operating voltages; anode, screens and cathodes will be kept in proportion but elevated by nearly 50%. The set does have a tendancy to motor boat at maximum gain and stations are frequently accompanied by a hetrodyne. I'm hoping that sorting the HT and then re-alignment will resolve these issues.

As for the Challenger, I'm hoping to find a nice MRF393 or 392 waiting for me at the museum to replace the deceased BAL0000L10 in the driver section. The way will then be open to start checking the 4CX350s finals, one at a time. Then the fun begins!

Thanks for your interest - Michael.

 

[Michael Oceanspan]

Hi Andrew,
Oceanspan works on 1.8, 3.5, 5 and 7MHz. 3.5 is very good, tuning on 5 and 7 is critical but do-able! Its debateable how useful the higher frequencies will be on AM, but it might make life easier for visiting CW operators who want to use the higher bands. Once the Challenger is up and running I might return to the Oceanspan in the Winter - unless Paul (curator) has some other winter projects to distract me!
Michael.

 

[Michael Oceanspan]

Hi Paul,

The Atalanta does bite! When it first arrived, I turned it on, twizzled the tuning knob as one does, found a station and just tuning in when the knob fell off. No worries, I thought, nearly got it, and took hold of the shaft to fine tune and you guessed it all the lights went out! Not mine - the RCD kicked in and saved the day, still got a healthy(?) belt though. A lesson well learned and not forgotten!

Michael.

 

[Michael Oceanspan]

I'll bear that in mind Andrew. Looks like another good reason to sort out the PSU section.
Michael.

 

[Michael Oceanspan]

Marconi Challenger

Paul, and others interested in the Challenger, can I refer you to the thread on the Marconi Challenger rather than repeat the story here?
In a nutshell, the replacement driver transistor arrived and is now OK. 4 new 4CX350s also arrived and am in the process of carefully fitting and setting them up. It's going well - so far!
73 Michael