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Old 18th Aug 2017, 2:00 pm   #21
G6Tanuki
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Default Re: T1154 question

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Originally Posted by trh01uk View Post
A feature of a rectifier followed by an L-C filter is its stability with load variations. When you have to do it twice over, its usually because ripple on the supply is a serious problem. In other words the equipment being powered is overly sensitive to ripple. When I simulated the original 1200V power system, I got a peak-to-peak ripple voltage of around 1.2 volts, and that was stable over load current from 80mA to 200mA.

The high performance of those mains power units points to the need to compensate the equally poor performance of the transmitter!
Also remember that the 1154/1155 ground-station transmitters were going to be running off 50Hz AC supplies, whereas the airborne versions would be run from DC dynamos, rotary convertors or engine-driven alternator/rectifier sets running at quite high RPM so the frequency of any ripple would have been a lot higher (so easier to filter, needing smaller/lighter components as befits aircraft use).

It's much easier to filter ripple at 400, 800 or 1600Hz than it is at 50Hz.

Voltage-regulation in the air would be my greater concern: I recall the electrical supply to the radios on V-bombers made extensive use of "Carbon pile" regulators [basically a stack of carbon-granule-filled discs with a spring to apply pressure to the electrodes at either end: an electromagnet wired in series with the carbon-pile stack opposed the spring pressure, reducing the amount of 'squeeze' on the granules if the current through the electromagnet coil increased, and allowing the spring to compress the granules more if the current was insufficient. This dynamically varied the resistance of the carbon-pile and so regulated current/voltage]

Another thought: were the 1154/1155-equipped engines also fitted with variable-pitch propellers? Variable-pitch props make it possible to constrain the RPM range the engine needs to operate over, by better matching engine torque to airspeed and load, which would in turn make regulation of engine-driven generators/alternators easier.
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Old 18th Aug 2017, 5:54 pm   #22
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Default Re: T1154 question

You could look at it from another direction- would any aircraft big enough, heavy enough and of the era to carry T1154/R1155, PSU and dedicated oppo not have had variable-pitch props and associated governors? The increase of efficiency, operating effectiveness and envelope flexibility with variable-pitch props meant that, once the complications had been mastered, they were rapidly and widely adopted between the Wars. Not least, a multi-engined, fixed-pitch-prop aircraft with a failed engine represented high and dangerous assymetric drag without the ability to feather, plus the worry and hazard of oil and fuel pumps continuing to run and possibly spray merrily around a maybe catastrophically damaged engine through unavoidable windmilling.
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Old 18th Aug 2017, 7:27 pm   #23
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The T1154/R1155 installed on aircraft were powered by a pair of rotary convertors which were run from DC from the engine-driven generator supported by lead-acid batteries. The rotary convertors were available in nominal 12v and 24v versions (closer to 14v and 28v being available when the generator was online). I'm not aware of them ever being powered from AC supplies, these were used by the likes of Gee or H2S.

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Old 19th Aug 2017, 12:18 am   #24
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Default Re: T1154 question

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My guess is that the trouble with crystals during WWII was that they didn't allow any frequency flexibility.
True, but the T1154 had its VFO preset on a handful of frequencies before it left the ground, and it wouldn't normally have been changed in flight by the W/op.
On a slightly different tack, I have been watching Youtube videos on R1155 restoration by "Mikrowave1". At the end he compares the R1155 with the BC348, which were quite similar in performance. However he notes that although the total production volumes were similar (80,000 and 100,000 units) the R1155 cost about a third of the BC348 to manufacture. The BC348 was mil-spec and the R1155 was 'good commercial' standard. This got me thinking: did the Air Ministry want a cheap and cheerful radio because they expected high operational losses? If the life expectancy of a bomber was only 30 missions there would be little point in putting a very durable radio into it. (This is quite a sobering thought.)
Alternatively, it may have been related to the fact that the 1155/54 was a crash development programme and it had to use available componentry and tooling. Or maybe they were just trying to save money.
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Old 19th Aug 2017, 9:54 am   #25
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I honestly don't believe there was any attempt to 'design down' the build standard of the R1155, it was typical of British military electronic equipment of the day, and certainly far superior to any commercial equipment. Compare it with Gee or Radar equipment, for example, or the WS19 used by the Army. The Navy used equipment clearly mid-30's in origin. Conversely the Americans simply had more money and more time to build equipment which was probably better than strictly needed, more akin to peacetime equipment expected to be in use for maybe a decade or more.

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Old 19th Aug 2017, 8:19 pm   #26
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Default Re: T1154 question

Andy and Mike,

in my comments about the design of the T1154 I wasn't referring to build standard at all. I was talking about the system design, the overall conception of the equipment. Questions like "Do we include a buffer stage between the VFO and PA so that the PA will not pull the VFO off frequency?" would come under that heading.

When I look at the T1154 in terms of construction I would say that it is typical of radios of the time. No other British military set was any better - at least none that I can think of, until the "experimental" WS42 was hatched by SRDE, and that introduced the idea of cast alloy chassis amongst other innovations. That idea probably came from inspection of captured German equipment - that was light years ahead of anything we were producing during WWII - though I have no actual proof of that statement because all the SRDE records during WWII have been lost.

To my eyes, the BC-348 is again typical of American radio manufacture. How does it differ, for instance from the AR-88 receiver, which was originally produced I think merely for radio amateur use before WWII broke out?

As a general comment I would say that all US equipment had a higher build standard than UK stuff during this period. Neither of course come anywhere close to German equipment of the same period.

Richard
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Old 19th Aug 2017, 8:32 pm   #27
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Default Re: T1154 question

Mike,

and as a general comment on your concern that the R1155 was "cheap" because the powers that be only expected an aircraft to last 30 missions, I would mention that the typical life expectancy of air crew on the bomber raids was three weeks! (Of course the variation was enormous with the first flight being very high risk, while some crew managed over a 100 flights)

I suggest its telling that when you hear from old people who bought T1154/R1155s after the war, they usually describe them as being "new in box". In other words they never flew anywhere - they were reserve kit which never got installed. The inference is that the installed stuff didn't survive!

Richard
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Old 19th Aug 2017, 9:26 pm   #28
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Default Re: T1154 question

The aircraft fitted with 1155/54 did have vp pr constant speed props yes, but recall that they also served in marine vessels which didnt. Boats generally have variable RPM to govern speed.

As for the reasons for designs, I am sure that the wonderful standard known as "good enough" would have come to the fore on an island besieged by U Boats and near starvation. There is no point in being better and more costly than "good enough".

Just my shillings worth

D
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Old 19th Aug 2017, 9:47 pm   #29
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I've never had personal experience of WW2 German electronic equipment, but from everything I've read I'm sure you're correct in saying it was 'light years ahead'. However I think the reasons for this aren't hard to understand, and they contained the 'seeds of their own downfall'.
Having spent 13 years working in Munich, it is clear that the German mentality is to do everything properly, you only have to look at the build standard of their infrastructure to see this. As a result, it is very expensive, and they won't release anything for use until it is complete and fully tested. This is good in peacetime, and wasn't a problem in their build-up to WW2. War was their intention, and they prepared properly for it, with first-class equipment.
However, once their master-plan to take over the world started to go down the pan, everything started to unravel. They couldn't bodge things to make it suitable for changed circumstances, like we could, it's just not in their mind-set. Equipment was so well-made it couldn't be repaired easily, as the plan didn't expect that to be necessary. Materials shortages and skill shortages meant that building new equipment to replace attrition became harder and harder, and they ran out of serviceable equipment.

So which approach, German or British, was actually overall more 'fit-for-purpose'? History gives us the answer...............

Andy
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Old 19th Aug 2017, 10:06 pm   #30
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Default Re: T1154 question

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The aircraft fitted with 1155/54 did have vp pr constant speed props yes, but recall that they also served in marine vessels which didnt. Boats generally have variable RPM to govern speed.
But, as Andy has pointed out - the speed of the engine (whether boat or plane) is entirely irrelevant when the power supply is a dymamotor running off batteries, which are charged by an alternator/generator system. The voltage under charge will have been fairly steady at about 28V (or in the rare case of a 12V nominal system, 14V), so we can assume that the HT voltages will have been stable regardless of the speed of the plane or boat.

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Old 19th Aug 2017, 10:19 pm   #31
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Default Re: T1154 question

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Originally Posted by M0FYA Andy View Post
I've never had personal experience of WW2 German electronic equipment, but from everything I've read I'm sure you're correct in saying it was 'light years ahead'. However I think the reasons for this aren't hard to understand, and they contained the 'seeds of their own downfall'.
Having spent 13 years working in Munich, it is clear that the German mentality is to do everything properly, you only have to look at the build standard of their infrastructure to see this. As a result, it is very expensive, and they won't release anything for use until it is complete and fully tested. This is good in peacetime, and wasn't a problem in their build-up to WW2. War was their intention, and they prepared properly for it, with first-class equipment.
However, once their master-plan to take over the world started to go down the pan, everything started to unravel. They couldn't bodge things to make it suitable for changed circumstances, like we could, it's just not in their mind-set. Equipment was so well-made it couldn't be repaired easily, as the plan didn't expect that to be necessary. Materials shortages and skill shortages meant that building new equipment to replace attrition became harder and harder, and they ran out of serviceable equipment.

So which approach, German or British, was actually overall more 'fit-for-purpose'? History gives us the answer...............

Andy

Andy,

well I don't think your analysis is correct. Firstly build standard was extremely high as you say. But it wasn't just build standard. The entire conception of the equipment was decades ahead of anything the Allies had. And that actually translated into a huge success in the early years of the war. Their Blitzkreig tactics relied on radio comms that the British couldn't even conceive of. While the British were still messing about with tanks that had no room for radios, the Germans had every tank kitted out with VHF radios that gave superb voice quality and was thus highly reliable.

My experience of the equipment was that it was not only well made, but in fact it designed to be easily maintained. That was an idea that had not even entered the thinking of the British designers. The German kit had plug-in modules for one thing, so you could quickly swop out one module for another. Another tactic was to make a single valve do every job in an equipment - even when the valve was apparently unsuitable in certain stages. Extreme cleverness shows up in that effort.

I really don't think you can blame the fact that the Germans lost the war on the quality of their equipment. If the equipment was so "unfit for purpose" why did the British then eventually - some 20 years later - then come out with equipment that started to get near to what the Germans had in WWII - and which copied so many of its concepts? I refer to the Larkspur radio system in particular. That shows a heavy influence of German design - and the first hints of that influence show up in the SRDE designed WS42. I met the person who worked for SRDE and who was responsible for evaluating all the German kit as it arrived over here during WWII.

At the simplest level, I think the Germans lost because eventually too much of the world was against them. They faced the combined forces of the Russians, the Americans and the British, with notable help from Commonwealth countries like Australia, India, New Zealand......As I recall they had war on three fronts at the same time - from the east, west and south and they were slowly overwhelmed. Victory was assured but it still took a very long time in coming.

Richard
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Old 19th Aug 2017, 10:39 pm   #32
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Default Re: T1154 question

From the German WWII radio equipment I've had a look at, I believe that their mechanical design and system concepts were very sophisticated, but I found the electronic design to be of a much lower level.

The Americans had the best-performing radio gear overall. They didn't go over the top on the mechanical aspects but it was well made and well designed. The British gear at the beginning was very crude and out-of-date. We made very rapid progress in design, but the build quality showed evidence of the desperate times. Just good enough was good enough. Where Britain excelled was in inventiveness. Microwave RADAR was really a game-changer. Huff Duff was another.

So like that old joke that you want to live in a world where the cars are German, the chefs French, the policemen British and the lovers Italian, maybe we'd like radios where the ideas were British, the Germans did the mechanical design and the Americans paid for it....

David
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Old 19th Aug 2017, 11:15 pm   #33
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Default Re: T1154 question

David,

I am surprised you say their electronic design was of "a much lower level". You say their system concepts were very sophisticated, so you must be referring to their circuit design.

If you look at a receiver like the E52 Koln receiver, it shows first class circuit design. We will take the systems architecture as being superior as you have already indicated that was the case. At the circuit level we have things like the variable IF bandwidth system using a crystal filter - where do you find anything like that in the US or UK equipment?

Then you have the remarkable demodulator, AVC rectifier and audio amplifier all using a single pentode valve. A mind boggling conception in my view. Then you have the extremely good stability based on advanced L-C construction techniques. Then you have the optical readout system. I could go on. At all levels of the conception - system, mechanical and electronic - it was vastly superior to anything that the US or UK produced.

Clearly that example does not fit your statement. Perhaps you had some other equipment in mind?

Even if we take the microwave Radar as being a game changer (which I would agree with), the advance here is not in circuit design. The innovation came purely from physics - its not really in the realm of circuit design at all - I would call that a systems improvement. There were some remarkably innovative circuit design techniques - notably from Blumlein - but as I recall, they were around before the microwave radar thing happened.

If anyone wants to get a quick overview of German radio comms - I think this presentation gives a fair picture:

Richard
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Old 20th Aug 2017, 7:18 am   #34
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Default Re: T1154 question

I did not mean that their electronic design was poor, rather that it was not in the same league as the mechanical design.

Variable bandwidth is a nice toy, but hasn't proved to be essential. All the Collins W-J and Racal receivers used post war by governments have switched filters of appropriate bandwidth to the intended modes. The sliding IF variable bandwidth scheme can be found in a few R&S post war models, and an awful lot of Japanese amateur radio transceivers up to the point when they all went DSP.

The Koln is a tour de force, but not suitable for aviation, not if the aircraft is wanted to get off the ground and I was thinking in terms of this being a thread about T1154/R1155.

I reckon the BC348 was probably the best suited to purpose HF receiver. The R1155 was a bit compromised to save material and labour, but they did the job.

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Old 20th Aug 2017, 10:12 am   #35
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Default Re: T1154 question

The T1154/R1155 project did not end up as intended. The Air Ministry over-egged the spec. and had to eventually settle for what could be done in the time. It was very late into service in any case, silly really as they were based on working commercial designs of the 30's.

For example, the R1155 was supposed to have something like push-button tuning. That didn't go well.
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Old 20th Aug 2017, 10:46 am   #36
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Richard.

I didn't say that Germany lost the war because of the quality of their equipment. As I said, at the start of the war it was indeed first-class. What I said was that once the war started to go against them, the quality of their equipment became its own worst enemy, they couldn't modify it or produce more of it in quantities to replace that lost in attrition.

A good example of the British ability to quickly bodge a design is in the use of the spare space in the R1155 to quickly introduce filters, first the 'Athlone filter' and then the various filters to cope with other transmitters introduced on the aircraft.

Ekco - you want an extra filter, certainly, we'll bend a bit of tin and mount it under the chassis, they'll be on the production line before the end of the week.
Telefunken - certainly, that means we'll have to make new chassis castings and a bigger outer case, the first will available in three months. What was that you said Fritz, the foundry was bombed flat last week? OK, better make that six months delivery.....
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Old 20th Aug 2017, 10:15 pm   #37
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Default Re: T1154 question

Andy,

well, you can turn that argument around and point out that no system designer worth his salt would have put the R1155 IF frequency on to the known frequency of a broadcast station in the first place. Chances are that the British didn't even know what a "system designer" was though, judging by the lack of them in the UK many decades later! Or to put it another way, you do not put out sets that will predictably fail to work in the field. Part of the job of an engineer is to study the requirement - not just the "requirements" that come from the "military/government/marketing" , but the other usually unspoken requirement that "the equipment will work"! How many specifiers actually state that? Usually none - because its so obvious that it shouldn't need to be stated. The need to retro fit the "Athlone filter" was total cockup - pure and simple!

Your example of Ekco adding filters internally is in fact a nonsense. If you build an equipment to a very high standard like the Germans did, you end up with excellent screening. That means a filter can be added externally, with the certainty that signals won't bypass it and just get picked up on the internal wiring as would have happened with the typical British equipment. My bet is that an external filter could have just been mailed out to all users - far quicker than any bits of bent tin which requires a recall of all sets already out in the field to fit them - or at least some time in a field workshop.

I don't know how many post deployment mods the Germans had (mainly because I am not a specialist in German war history at this level of detail). But my bet is that they didn't need a lot of extra filtering because the performance was so good, that such problems would have been rare. Arthur Bauer would be the person to comment on this, I think.

Richard

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Old 20th Aug 2017, 10:36 pm   #38
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Default Re: T1154 question

I might add to my post above that we are now getting down to questions that underlay the "T1154 chirp" case. Questions like "How do we get the specification right?" "What is a good product anyway?

The question for this thread - which focuses on the chirp of a T1154 - is whether that was truly a "defect" or not? Radio amateurs certainly think of it as such these days because they are used to Japanese boxes that produce a rock steady CW note, completely free of all hum, modulation etc. Sure a skilled intercept operator could tell from the chirp that a T1154 was in use. But that information is of little use if the message being sent has such a short lifetime that you have no time (as an enemy interceptor) to take meaningful action as a result of the intercept intelligence.

Its reasonable to assume that no long term messages (e.g. information about battle plans for the next month or two) were ever sent via a T1154! I don't know the Allied policy on sending of such messages, but I wouldn't be surprised if sending them by radio was totally prohibited - in favour of landline or despatch rider.

Richard
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Old 21st Aug 2017, 7:05 am   #39
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Default Re: T1154 question

Weren't there a few occasions where British cable ships were used to sever undersea cables specifically to force valuable messages onto radio links?

Recognition of a T1154;s distinctive note might have revealed that there were bombers about, though 1154/1155 sets were also used in some boats. (steel cased ones)

David
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Old 21st Aug 2017, 7:38 am   #40
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Default Re: T1154 question

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Weren't there a few occasions where British cable ships were used to sever undersea cables specifically to force valuable messages onto radio links?
If it's of any interest, David, I have a book entitled "The Thin Red Lines", a post-WW2 history of Cable and Wireless. The early chapters cover cable-cutting and it was not just Britain that practiced this, for instance Italy cut five of our cables in the Med upon her entering the war.

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