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Old 1st Dec 2020, 7:48 pm   #1
jamesinnewcastl
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Default Standard Beam Approach - Rebuild update

Hi All

I dearly wanted to have a long post detailing the restoration of a version of the Standard Beam Approach (SBA) System, however life gets in the way and it goes too slowly and the moderators rightly closed the thread.

So here is an update!

Attached is a photo of all the parts necessary to rebuild the Marker Receiver R1125. The caps and resistors are essentially 'new' as they are restuffed or remade. You can see an aluminium 'frame' which has the same size and shape as the original casting with all the same holes. Many components are in fact original as there is no way of making a new replacement.

My original plan was to rebuild the receiver on the Al frame so that I could get at all the components to allow all the various voltage measurements, etc. The thought being that the original design wasn't so hot and that I might need to change component values so why build the thing into an inaccessible casting?

In the cold light of day I've realised that I should build a version on the frame using modern components where possible until I am happy that all is working - then put it all into the original cast chassis. So that is what I plan to do. Watch this space! For those of you who know the system - this is the only one that could drive the neons on the Pilots instrument.


James
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Old 1st Dec 2020, 7:51 pm   #2
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Default Re: Standard Beam Approach - Rebuild update

Those of you avidly following my SBA posts (you know who you are!) will remember that I wanted to rebuild the original Test Equipment for the system, while there are a few items of such kit, I concentrated on the 'Oscillator Type 12'. It seemed obvious that none of these could possibly have survived the war as they must have been few and unloved. Attached are some images of the kit from the RAF AP and some of my 3D models of the planned rebuild.
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Old 1st Dec 2020, 7:53 pm   #3
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Default Re: Standard Beam Approach - Rebuild update

To my delight a few weeks ago I was contacted by a fellow forunite RAGtime who asked if I had obtained any of the front panel meters as he needed one for his Type 12!!!

Deep Joy - it turns out that RAGtime, a Dutchman living in Brussels, had wandered into a flea-market held in a local church in Uithoorn (NL) in 1975/6 and picked up a Type 12. It was in a box with some other equipment. He wasn't sure what it was but has hung onto it for 35 years and happily it looks very much complete apart from some fidding with the power leads. The original wooden box has gone along with the metal enclosure - probably re-purposed, but all the important items remain!

RAGtime notes that old Schiphol - the original Amsterdam Airport from 1928 till 1967 - is just 10 km away from Uithoorn. it seems likely that it drifted as war surplus when the war ended.

So here are some pics of the unit in all its glory including some original crystals! I'm just gob-smacked that one Type 12 has survived!

Cheers
James
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Old 1st Dec 2020, 8:46 pm   #4
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Default Re: Standard Beam Approach - Rebuild update

Impressive. My SO is at the “all-new Schiphol” right now. I’ve little hope that she’ll find such a useful bit of kit…
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Old 1st Dec 2020, 11:30 pm   #5
M0FYA Andy
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Default Re: Standard Beam Approach - Rebuild update

James, it's excellent news to hear that a Type 12 has turned up. I hope you now have a comprehensive set of high-resolution pictures of it to enable you to build an accurate replica.

Andy
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Old 2nd Dec 2020, 9:03 am   #6
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Default Re: Standard Beam Approach - Rebuild update

James,

Your finding of a Type 12 Oscillator - albeit in Brussels - is a fairly typical example of how "most things are out there somewhere". It is quite astonishing what survives in dark corners and cupboards somewhere, and forums like this do help to rediscover bits of our history. Chances are that there are more out there.....

Fortunately most electronics is of a relatively modest size, and can thus be put into ordinary domestic sheds and attics where it does sit until someone "finds it". In my experience its generally the things that were only made in very small quantities or are inconveniently large (I'm thinking of things like a SWB-5 transmitter) that don't make it somewhere.

It's great that you have this project running - not aware of another one anywhere! Please do keep us all updated!


Richard
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Old 2nd Dec 2020, 10:20 pm   #7
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Default Re: Standard Beam Approach - Rebuild update

Hi Again

Andy - Yes, Rob is working hard to measure up all the various dimensions. I'm not getting them on the model as fast as I should though. He has also sent a good many high quality pics.

Richard - I think that I got a good deal of my SBA kit from you!

I had thought to delay the project again by building a mains operated power supply, but after another 'doh' moment I realised that I already have the power supply that I need as I have already refurbished the one that came with the system!

Pic attached of the lab area starting up - a 12V power supply to power the grey PSU box top right, a scope and a Synthesised signal generator for the RF input. The pilots instrument on the shelf.

James
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Old 2nd Dec 2020, 10:22 pm   #8
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Default Re: Standard Beam Approach - Rebuild update

I may have posted this before but this is a video of the PSU in operation

https://www.youtube.com/watch?v=uQkvqxEHTYY


Cheers
James
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Old 4th Dec 2020, 9:47 pm   #9
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Default Re: Standard Beam Approach - Rebuild update

Thanks for posting about that video. I hadn't seen it before. A nice simple demo of a early voltage "transformation" and "stabilisation".

Richard
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Old 5th Dec 2020, 7:27 pm   #10
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Default Re: Standard Beam Approach - Rebuild update

Hi Richard

It's the same PSU that you sold me! The neon is new though.


James
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Old 7th Dec 2020, 12:12 pm   #11
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Default Re: Standard Beam Approach - Rebuild update

James,

that's good - glad to see its being put to good use, and actually working. We actually had a lot more SBA stuff, and that all went to a museum - sadly a very much doubt they have done anything with it than put it on a shelf somewhere.


Richard
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Old 21st Jan 2021, 6:33 pm   #12
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Default Re: Standard Beam Approach - Rebuild update

Hi

Just a small update - I've bought one of the other items of test gear for the SBA system. It's not much in terms of functionality but it means that there is only one other item of test equipment as yet unfound.

It is a simple unclaibrated AC voltmeter used to set up the SBA system - probably tuning for 'max gain' approach although the set-up procedure I have actually suggests that The Universal Avometer is suitable and implies that 75V is a good range to select!

Picture attached - it looks like a good long piece of connection cable, the AP suggests 30 feet, we will see when it arrives.

Cheers
James
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Old 4th Feb 2021, 2:13 pm   #13
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Default Re: Standard Beam Approach - Rebuild update

Whooo Hoo - It works!

Hi - in the next post I have put links to YouTube videos of the refurbished R1125 working again! Well the first part at least....

I've rebuilt it so far onto a jig so that I can get into it with scope probes etc, and to make any soldering/replacements easier, pic attached.

What you see on the scope is the modulated output from the (rather splendid for the very cheap ebay cost) SSG1000 Farnell signal generator. The top trace shows the output of the first valve which is a "simple cumulative-grid detector with anode voltage controlled Reinartz reaction". This drives the second valve being an audio amplifier whose anode load is a transformer with two outputs, each of which is tuned to a different frequency namely 700 and 1700 c/s. Yes tuned - there are some hefty toroids in there.

So in the first video the system is powered up using the original motor/generator power unit (you can hear it powering up and running). The carrier frequency is slowly increased as you can see on the read out with the modulation at 1700 c/s. As the carrier hits the tuned frequency you can see the O or 'outer' neon strike on the pilots instrument (top right). The carrier is also pulsed in the actual system and I simulate this using the SSG1000 carrier on/off control. The pilot would normally just see this neon pulsing as he passed over the Outer marker.

The next video is the same but with the carrier modulation at 700 c/s, this time the I or Inner neon strikes - not quite so bright for some reason.

Technically this is not great achievement nor is the circuit anything to write home about but I hope to show soon that it also generates the warning audio for the pilot and acts as an audio amplifier for other parts of the system. Not bad for a couple of valves.

Later, one day, I hope to restore the remainder of the system with the guidance signals operational and everything back in place!

Cheers
James
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Old 4th Feb 2021, 2:15 pm   #14
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Default Re: Standard Beam Approach - Rebuild update

Here are the links to the You Tube Videos:

https://www.youtube.com/watch?v=gJMq_cirHLI

https://www.youtube.com/watch?v=03Lyxbwez_w

Cheers
James
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Old 4th Feb 2021, 4:46 pm   #15
M0FYA Andy
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Default Re: Standard Beam Approach - Rebuild update

Excellent progress!

Andy
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Old 7th Apr 2021, 3:01 pm   #16
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Default Re: Standard Beam Approach - Rebuild update

All

The next stage is to produce a signal fully representitive of the three transmitters to be found in the system namely the outer marker, the inner marker and the main 'Beam' transmitter.

I had a false start with some 555 circuits and googling 'controlled attenuator' unsucessfully. However googling 'controlled RF attenuator' produced a cheap chip on a small pcb for a few pounds that took 6 digital inputs and produced a wide range of attentuation. Naturally I had to wait 5 days for it to be shipped from China!

The final item pictured below is an Arduino on top of which is impaled a small vero board and impaled on that is the RF attenuator. Apart from taking the Arduinos outputs from 5 to 3.3V there is very little circuitry. All power is from USB (but I could add a 9V battery), 3.3V from the Arduino.

The simulator takes in a modulated RF from an external signal generator and performs the appropriate attenuation as required, namely:

Full on, Full off for specified periods - medium speed
Full on, Full off for specified periods - fast speed
One period of x amplitude and one period of y amplitude - X and Y being variable

The front panel controls are:

Select Outer/Inner/Beam function
Increase/decrease output
Left/Right variation
On/off (for battery if fitted)
USB Connection

The next part is to make a video of the R1125 in operation with the accurately simulated signals. I have also added a 1940's RAF earpiece to the rig so the sounds will be that little more accurate. (The price of these earpieces is astronomical!)

I'll produce a video soon and supply the link.

Cheers
James
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Old 10th Apr 2021, 1:13 pm   #17
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Default Re: Standard Beam Approach - Rebuild update

Ok Video made and published:

https://youtu.be/eO3AW5a6Yac

It was a bit disappointing as a project as it worked the very first time I powered it up, and even before any fiddling! However it has started to play up so there will be some learning involved!

Once I'm happy with it I'll tidy/bind the wiring (all new cotton covered), clean and install the connectors then drop it all back into a re-sprayed cast enclosure. A check to see that all is well then it goes back in a cupboard and I'll start on the main receiver which should allow demonstration of the glide path function and get the two needles moving on the Pilots instrument!

Cheers
James
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Old 24th Aug 2021, 12:57 am   #18
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Default Re: Standard Beam Approach - Rebuild update

Hi All

Finally (99%) completed the Marker Receiver restoration by putting the gubbins back into the restored case. Photos attached show the unit in comparision with the AP images from the 1948 issue of AP1186. The serial number on the unit is just 6165. I'm going for restoration of the very first version of the SBA in WW2.

The AP photo has no red line implying that it is the original American version which was the same, but had American threads on the connectors. The cast lid is different and there is a nice label on the original which would have been the 'Standard Radio' logo. The holes that the label was screwed to have been filled in my restoration - no doubt because it was manufactured by another company or the unit needed to be annoymous to prevent crashes in enemy territory revealing where the unit was made.

I will be making up one of the labels and changing two bolts then the task is really complete!

Cheers
James
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Old 24th Aug 2021, 1:11 am   #19
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Default Re: Standard Beam Approach - Rebuild update

The next part of the system to be restored to new and working condition is the main receiver (see pic). All resistors changed for new, caps restuffed and the unit cleaned and resprayed. Polishing as appropriate and a new small cover panel needs to be made.

A change of approach this time - I will assume that it is going to work so I won't build it out of the case on a jig but commission it in situ. I will have to strip it all out though to clean and respray.

Once completed this unit will be operating the two meters on the pilots instrument making it fully functional.

Tomorrow I will show the development of the Marker receiver in a few posts!

Cheers
James
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Old 24th Aug 2021, 11:55 am   #20
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Default Re: Standard Beam Approach - Rebuild update

Hi

A quick look at the development of the Marker Receiver.

The attached image shows a few of the receiver designs. Top left is the oldest, stuffed with components and a triode and a pentode. This design detected the Marker transmissions to indicate the distance to the runway, it provided a pre-amp for the audio circuitry and it lit neons to indicate which sort of marker was being crossed. Nice set of functions for a small unit. It did require a stabilised supply for the reaction Triode however.

The pilots didn't like the bright neons and were happiest using the audio indications of the system. Initially the ground crew simply removed the neons but in all the other three units in the picture you can see that L1/L2, the three potentiometers and many components went. The transformer in the top left lost a few windings too and became much simpler. The last main change was the addition of a second RF connector to allow the connection of a simpler single connection antenna. The triode was replaced by a pentode with the stabilised supply now connected to the second grid. The system had its own motor generator, later systems also included an external carbon pile regulator to further tame the aircraft supply variations I suppose.

For the war effort I assume that the cast enclosure of the first design was replaced with a simple steel enclosure. The initial design had an RF gasket to seal the poor lid connection, the steel unit had a big overlapping, close fit lip which I assume provided RF rejection. The components often had their part number carefully painted on, perhaps labour was cheap!


Cheers
James
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