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Discussion Starter · #21 ·
I am pleased to announce that the Museum's Marconi Challenger is now working! Reports received on Saturday morning following the VMARS' 80 metre net indicate that signal strength is very good and excellent audio, so all in all a very pleasing result.
There is a fly in the ointment: the drive protection circuit trips out randomly and for no apparent reason, which is annoying. There are five lines going to the protection circuit and they are the same status in both fault and no-fault conditions. It's not overheating, which would worry me, as I can see the bi-metallic strip that detects valve box air temperature >125DegC is still open. So far I've only checked the input lines with a voltmeter. On Monday I'll a) check them with a scope incase there is noise on one of the lines and b) failing that I will check the circuit backwards from the trip relay to see where the fault is registering.
Picture attached.
 

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Nice work, Michael, and nice photo (liked the white mug inclusion, adds a bit of homeliness). Nice to see a decent photo of the equipment in all its glory.

Hope you have success in locating the fault you mention. How does one select the exact frequency? Is it just keyed in via the keypad at lower right, or is there a variable control, as in the older sets?

Best of luck with the TX, and well done with your work so far, especially in finding a replacement which works for the power transistor you mentioned.

Paul
 

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Excellent indeed. I'll be in touch about a visit. My arm is twitching at the thought of keying that transmitter.

Can you tune up on 472.5 KHz? I made a few contacts on that band using my T1154, including Finbar ex EJM.

Ah, tripping out. The Oceanspan never did that even if it wouldn't tune up because of the salt spray in a cyclone. At least it's not blowing the HT fuse.
73
Andrew
 

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Discussion Starter · #24 ·
Challenger now fixed - fingers crossed!

The Challenger has two protection circuits: 1)the HT protection trips if the bias supply fails or the airflow through the valve box fails, a drawer is opened, or excessive current is drawn; 2)the drive protection circuit, the one giving me problems, trips if final valve air temp exceed 125DegC, critical controls are moved after tune up, frequency data input is incomplete, or the PLL drifts out of lock. If any of these last four faults occurs the drive trip LED illuminates, but it doesn't tell you which of the faults have occurred. Another annoyance is that not all of the fault lines coming into the protection circuit are, for instance, low for no fault, Hi for fault. Some are high, some are low. Anyway I made a simple table of the status of all four lines under no-fault conditions, measuring them again under fault conditions gave the same readings on a meter. So was it a transient fault or noise on one of the inputs, or even a fault in the protection circuit itself?
The whole thing was frustrating on Saturday as I was able to make some good contacts on 80Metres, but the drive would trip out part way through.
I decided to spend today (Monday) sorting it out. I made a small board to fit onto the header for the drive protection circuit with four LEDs to monitor each of the fault lines. Powered up the transmitter and it behaved perfectly for about 2.5 hours. It did trip while I was probing after everything was well warmed up. I decided that it was time to apply the Mk1 test strategy and give it a good thumping! A healthy tap in the PLL area caused it to go reliably out of lock and trip the drive. Some gentler tapping with the plastic end of a screwdriver indicated something sensitive in the area of the divider chip, gave it a push into its socket and the problem went away. To make sure I removed and reseated both the divider and the synthesizer chips. It was obvious from the condition of the pins that they had been removed before a few times! That seems to have fixed it. It behaved itself for about 2 hours this afternoon and would not suc***b to any amount of abuse.
Picture of synthesizer draw attached. PLL in screened box on right, drive protection circuit on large board right of centre under long shaft with two UJs.
If anyone is able to listen in, I intend to join in the VMARS 80 Metre USB net on 3.615MHz on Wednesday evening between 20:00 and 21:00.
Michael (GW7BBY/GB2MOP)
 

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Discussion Starter · #25 ·
Andrew, I did tune it into the dummy load on 500KHz this morning, didn't try it on the antenna. Our Antenna will not be very efficient, its an inverted L, 45metres on the top section and 15 to 30 metres on the vertical part depending upon how high the mast is cranked up! However, the losses will probably be enough to keep it within legal limits!
Michael.
 

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That's a nice-looking piece of kit, Michael. Takes me back. Glad you were able to at least temporarily sort the tripping problem. Might need to solder the IC's into the PCB, without the sockets, which as we all know, can give problems occasionally. Quite surprised that sockets for IC's were in use for sea-going equipment, come to think on it.

Thanks for the photos you post from time to time. Appreciate it.

Paul
 

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Andrew, I did tune it into the dummy load on 500KHz this morning, didn't try it on the antenna. Our Antenna will not be very efficient, its an inverted L, 45metres on the top section and 15 to 30 metres on the vertical part depending upon how high the mast is cranked up! However, the losses will probably be enough to keep it within legal limits!
Michael.
How's the earth system? That is the most important thing...
 

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Our Antenna will not be very efficient, its an inverted L, 45metres on the top section and 15 to 30 metres on the vertical part depending upon how high the mast is cranked up!
Michael.

That's a hell of a lot better than the antennas presented by most new-builds in the 1990s when that transmitter came out!

Make sure you have good earthing and with that transmitter, the World's your oyster.
 

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Yes, excellent work Michael.
They don't make transmitters like that any more, that is, something you can fault-find on and fix on the pcb. Those pcbs were laid out by draughtsmen with tape and pads, whereas I went straight to CAD in 1987 when I started my own business, and I abhor wiring soldered to boards.

UJ puzzled me for a while but you have lots of those in the museum. I call them flexible couplers.
73
Andrew
 

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Hang on! #18 : The Marconi 'Alert' receiver didn't have 24V capability, did it? My memory must be going a bit off. Just can't remember much about it now. Obviously you had the 'Salvor' on 24V but the receiver? Don't think so. In that case, did you have the capability of receiving anything at all without the ship's generator being operational? Anyway, the rude comments about the 'reserve' receivers stands. They were heaps of c..p! (In my humble; don't want to hurt anyone's feelings!)
 

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Michael: Just re-read your posting a few weeks back on the 'Oceanic' receiver, of which you have two at MOP. Now that set has all the IC's embedded firmly into the PCB, by the sound of it. Why didn't they do the same with the associated 'Challenger', I still find myself wondering. If you want the board fixed, just send it out here, along with all the IC's... love doing work like that. And for such a good cause!

Paul
 

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Mike, last night about 2020 you were weak and unreadable in Penllergaer but I heard the loud and clear reports you were getting from Holland and France. By 2052 the ionosphere favoured you and I thought the quality of modulation perfect. A previous station with heavy AVC, clipping and filtering was unpleasant to copy, but no doubt effective in army communications.

As for the Alert, somebody remarked that switched on or off the result was the same. However, it met the specification for a watchkeeping receiver, and if ships used CW instead of MCW it had no chance. Auto Alarms were more sensitive. I often used the DF for 500 watch whilst away on HF.
73, Andrew
 

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As has been said, the Alert operated from 24V and met the regulatory requirements (if maybe not the operational requirements) for a 500 kHz emergency and watch-keeping receiver. It was designed to receive MCW signals only, on the assumption that stations would comply with the the current ITU Radio Regulations requiring use of that type of signal on 500 kHz. Transmitters of the same era, such as Oceanspan, only produced MCW signals when 500 kHz was selected. Later designs would permit the operator optionally to select CW.

I was a firm believer that MCW was the mode to use for distress and safety calling and never used CW on 500 kHz - the purpose of a call was to attract attention so it made sense to me to make as much noise as possible! I believe auto-alarm receivers were not required by regulations to respond to CW and some designs did not.

So although the Alert was rubbish as a communications receiver, it could serve in emergency for communication with nearby ships involved in providing assistance to your ship when you were without mains power. That is the function required by the regulations.

Having said that, I much preferred to sail with Mercury/Electra rather than Atlanta/Alert since I was happier having two decent receivers for MF use than one excellent one teamed with a dud. When the ship's power went down, I still felt capable of dealing with things and keeping the radio room operating.
 

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Discussion Starter · #35 ·
Challenger Transmitter Working - Replies.

A few of you have raised points about Challenger and associated equipment.
Andrew, I am pleased that you were able to listen in on VMARS on Wednesday evening, Conditions were atrocious, not just atmospheric noise, but adjacent stations overlapping our transmissions and tuning up nearby. However, it was a great pleasure to run the Challenger for an hour and to get some very encouraging reports. Oddly, and this applies to my home station in Llangeler as well, there are a number of stations in the Swansea and Merthyr area that are barely audible at the best of times, yet at the same time we have no trouble with the rest of the country or even northern Europe - geography I guess. Will we see you at the Crank-Up this weekend, Sat and Sun? ( I doubt I will be able to demonstrate the Challenger as with everything else running in the Museum, there won't be enough amps left for me!)
Earthing: At present it is earthed to the lattice mast, which is in turn well earthed. A good method I found with the Oceanspan was to connect the ground side to the tin roof covering the Radio and Telehone areas and about 10 metres or so below the horizontal part of the inverted L. I tried it briefly with the Challenger, but didn't seem to be any improvement. It is something to be addressed during the winter shutdown as there is scope to improve the antennas, in particular the receive side. We can get out far better than we can receive.
Paul: Oceanic and IC sockets. Most of the more common (cheaper?) ics in Challenger are in fact soldered directly to the boards. Only the bigger ones such as the 40 pin Divider and Synthsizer chips are in sockets and, guess what, these are the ones that cause problems! It is actually the same in the Oceanic: most ICs are soldered, but the processor, EEPROMs and a few larger chips are socketed. I might take you up on your offer and send you the Oceanic boards and a bucket-ful of TTL.
As you like my pictures so much, attached are left, right and top views of the RF unit.
Finally, I must mention that this project has only been successful through the generosity of EIMAC (now part of CPI) who actually donated the four 4CX350s to the project. The museum would have found it difficult to justify the cost of £1000.00 + worth of valves.
73 all - Michael.
 

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Bring it on! Very willing to help out with the boards. I worked for many years in various types of electronics factories, after I left the sea in '82, manufacturing equipment and doing lots and lots of PCB work, including the dreaded surface mount types. In fact, was still working at all this as recently as 2007, until we emigrated to NZ. Soldering in the 80-odd pin surface mount IC's by hand onto a brand new board was quite challenging (no pun intended). So the offer is a genuine one. Thanks for the photos as well, and taking the time out to reply to all these posts.

Best regards, Paul
 

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As has been said, the Alert operated from 24V and met the regulatory requirements (if maybe not the operational requirements) for a 500 kHz emergency and watch-keeping receiver. It was designed to receive MCW signals only, on the assumption that stations would comply with the the current ITU Radio Regulations requiring use of that type of signal on 500 kHz. Transmitters of the same era, such as Oceanspan, only produced MCW signals when 500 kHz was selected. Later designs would permit the operator optionally to select CW.

I was a firm believer that MCW was the mode to use for distress and safety calling and never used CW on 500 kHz - the purpose of a call was to attract attention so it made sense to me to make as much noise as possible! I believe auto-alarm receivers were not required by regulations to respond to CW and some designs did not.

So although the Alert was rubbish as a communications receiver, it could serve in emergency for communication with nearby ships involved in providing assistance to your ship when you were without mains power. That is the function required by the regulations.

Having said that, I much preferred to sail with Mercury/Electra rather than Atlanta/Alert since I was happier having two decent receivers for MF use than one excellent one teamed with a dud. When the ship's power went down, I still felt capable of dealing with things and keeping the radio room operating.
Hello Ron

I sailed a lot with the next generation of rx'ers: Apollo/Sentinel/Lifeguard N.

The Sentinel was good as a MF working rx, and I used the Lifeguard N (with BFO) as a 500 watchkeeping rx.

I was only thinking of your comments re main tx'ers not being powered from the emergency gene circuit the other day...what a great advantage that would have been - run the whole radio room on that circuit....

On my first ship, both rx'ers automatically switched to 24v if the mains failed....another excellent idea, way ahead of its time...

But, of course, typical parsimonious shipowners....and an IMO dominated by Panama and Liberia...
 

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In my experience the radio room supply was from the Emergency switchboard. Not by regulation but pragmatism.
 

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Problem was that the main tx often needed a 3 phase supply...
Once I became technical manager at MIMCo I stopped all that 3-phase nonsense. It had never made sense to me - after all, the Crusader required less power than our kettle at home and we didn't have a 3-phase supply to the house. All new designs started for me had to be single phase devices capable of running from the ship's emergency generator supply. The Challenger, our most powerful transmitter was just the latest and last "traditional" (i.e. manually-tuned) design the company produced.

I suspect that MIMCo went down the 3-phase path accidentally, in the early days post-WW2, simply because design of their transmitters (and most other equipment) was carried out by engineers of Marconi Wireless Telegraphy - producers of high-power broadcasting, point-to-point and military transmitters. They were familiar with such techniques and would have felt happier using existing designs rather than starting from scratch. Big commercial organisations can resemble VLCCs in that it takes a lot of time and effort to turn them round once they have adopted a policy. MWT, with its inherent assumptions - that because they were the first, they were the best and could not be wrong - was an almost unstoppable force.

I failed to stop Conqueror being 3-phase but persistence made it the last of our transmitters to be designed that way. Everything from Commander onwards was single-phase but we still had little success in persuading many builders and owners of newbuilds to connect the radio room supply to the ship's emergency generator - they were even more difficult to convince than MWT. If it wasn't a regulatory requirement, it wasn't going to happen as far as they were concerned.
 
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