Transmitter type T1509A

[trh01uk]

Sean,

the NZ advert reference to an "ATU" is just a confusion. This document

http://www.rnmuseumradarandcommunica...org.uk/617.pdf

which is the naval description of the T1509, clearly lists the "transmitter unit" as "type 59" with the same stores ref no. 10D/1758. So this supposed ATU is just the top deck unit.

Technically the pi-output will match a range of aerial impedances, so some might regard this as a sort of ATU. However the coax output socket will flash over before getting to any really high impedance levels.

If this ATU that you have been offered is real (and not just the top deck of another T1509), then it might be a remote ATU used at the end of a coax feeder. That would certainly fit with the normal use of this Tx, where the aerial would have been a considerable distance from the unit, with a long length of coax feeder in between.

Richard

[Sean Williams]

Hi Richard,

Indeed, Hendon is the Museum.

You appear to be thinking along the same lines as I am - the type 59 as you say is the transmitter assembly, so I do think that this will be a remote unit if anything.

Will keep you posted as to the results of my research....

Sean

[Sean Williams]

Seems there is a matching tuner for the 1509.....

[M0FYA Andy]

Quite fascinating!
It does make me wonder what was the fate of that transmitter, and given that one of my non-radio interests is impulse clock systems, what about the Synchronome, does that survive?
Is it acceptable for me to post the RSGB article on the Electric Clocks forum?
Andy

[Sean Williams]

I wouldnt think it was an issue - just credit the RSGB for their work...

[trh01uk]

Sean,

yes, interesting article you have turned up. I note that the "aerial coupler" sitting on top of the Tx was actually made by an entirely different company. Tx by EMI and coupler by Odeon Radio. (And odd thing here is that I thought the T1509 was produced by Marconi - maybe my memory is failing me here - or maybe they were produced by more than one company.)

Its likely that the T1509 had a commercial designation (since the company was able to present one to the RSGB) in 1948, when it was simultaneously in service with the RAF (and the designation "T1509" doesn't appear in the article). And it thus quite likely that the RAF never bought the aerial coupler. It will need some delving into the detail of RAF aerial systems to find out whether that was the case or not.....

Another interesting question is how the RSGB ever got permission to use a T1509 on the amateur bands. Its quite easy to push around 400 to 500W into its PA, which is somewhat above the 150W limit......


Richard

[Sean Williams]

Richard, 'twas Colin Guy (G4DDI) that opened this can of worms for me - interesting stuff for sure!

I have seen references for the T1509 being produced by Cossor, there are switches inside that were supplied by STC - so it's anyone's guess where they originally hit the drawing board.

I think a trip to the PRO might be in order, I can then hopefully secure the procurement documents, and some idea of the original design brief.

In the meantime seeing as Marconi are the only company still in existence I will have a stab through the back door there....

Looking at the RAF antenna erector's website there are several antennas that would benefit from an ATU, however, I am in contact with past serving staff from RAF Greatworth - there are no recollections of ATU usage on that site.

Researching Military Electronics is a great challenge!

Sean

[onewatt]

Hi Peoples,

I agree an interesting article. It goes along with the description I've been given, that it's not a remote unit and condition is straight out the packing carton. I'm hoping to get an equipment id designation shortly which hopefully will assist.

I haven't got the actual clock but will this pass off as replica?

Chris

[trh01uk]

Chris,

I think you misunderstand the word "remote". A remote ATU can be 1 foot from the Tx or 1000 feet (or more). The point is that it is not part of the Tx itself.

It is in fact bad practice to run an antenna right into the building (as the RSGB apparently did) because you end up putting high RF fields into the operating area. This can produce sparks and RF burns off non-grounded metalwork, and some people suffer severe headaches when there such fields about. With 400 - 500W of RF around, it could also be pretty dangerous. And apart from all that, it compromises the operation of the antenna, since RF is going places you really don't want it.

Sometime during WWII, the practice of building ATUs into transmitters seems to have stopped, and coax outputs provided (as here). The ET-4336 is a pre-war example and the T1509 a post-war one.

One report I saw from someone who used the T1509 when in the RAF was that there were a large number of them installed in a transmitter hall. And these were fed out via coax feeders to the antenna farm some way away from the building. Whether there were any ATUs at the end of these coax feeders I don't know - it would depend on whether the antennas were resonant (and thus matched to the feeder), and whether they needed frequency agility without adjusting antenna wire lengths. No doubt Sean's investigation will tell us more in due course......

Richard

[Alistair D]

The size and weight of these transmitters dictated that they were for fixed station use. Fixed stations would never have had random aerials that required external ATUs. I doubt that an external ATU was ever designed specificly for the T1509.

Al

[M0FYA Andy]

Sorry Chris (onewatt), nice try but that clock just won't pass muster as a replica of a Synchronome! It is a Magneta Hipp-toggle type, closely related to the PO36, a different animal entirely!
Andy

[trh01uk]

Originally Posted by Alistair D

The size and weight of these transmitters dictated that they were for fixed station use. Fixed stations would never have had random aerials that required external ATUs. I doubt that an external ATU was ever designed specificly for the T1509.

Al

I agree with you that fixed stations would normally have aerials designed for the purpose, covering all the frequencies (and directions) required. In some cases they would have had broadband aerials, like a rhombic. Thus, as you say, no ATU would be needed.

But your point about the size and weight of the T1509 is misleading. Bigger transmitters than this were being put in trucks before WWII and long afterwards as well. Consider the WS53 in Bedford QLRs, and later on Austion K9s. Or even later on consider the D11/R234 monster (which is about 2.5x bigger than the T1509) which was also put into a K9 (3 ton lorry). The squaddies complained that the truck was overloaded, but that made no difference......


Richard

[Sean Williams]

I have seen a picture, and the AP alludes to "Mobile Use", in this case, it was being used as a temporary station, while RAF Gan was being constructed.

Cheers
Sean

[Alistair D]

I hadn't thought of that kind of 'mobile' What kind of aerials would have been used.

I presume they would still be mains powered which would make them transportable rather than fully mobile.

Al

[onewatt]

Hi All,
Duly noted Richard and Andy. I can see this project will be expanding some what.

Chris

[trh01uk]

Originally Posted by Alistair D

I hadn't thought of that kind of 'mobile' What kind of aerials would have been used.

I presume they would still be mains powered which would make them transportable rather than fully mobile.

Al

Al,

well, generally in the Army, they used simple whip aerials mounted on the vehicle while moving. Back before WWII there was a project called something like "the 100 mile R/T transmitter". Its aim was to achieve 100 mile range, while on the move, between two mobile stations.

That is a pretty tough assignment, since we are talking ground wave here, which becomes more and more difficult as you go up through the HF spectrum (i.e. path loss increases with frequency). And you need hundreds of watts of AM to do 100 miles even at around 2MHz with something like a 16' whip.

And then you can't readily drive about with 16' of metal waving in the air, cos it hits trees, bridges and power lines and tends to break off (or short the power line to ground, while taking out the transmitter.....)

And when you solve all that, you have the problem of shoving 300W+ up your whip, and you find the voltage at the bottom is something like 10,000 volts, so you need wacking great big insulators (and large instruction notices telling the squaddies not to touch when someone is yacking.....)

You make a good point about the problem of providing enough power to make all this go. The Bedford QLR had built-in mains generators on the lorry. Whether this could readily run while in motion I am not sure without checking the literature.

The later D11/R234 station did tow a large 3.5kW geny behind the lorry, and again I am not sure (off the top of my head) whether this could be run while driving along. I tend to agree with you that these stations look more like a transportable than a true mobile, and you could definitely have a much more effective station when you stopped, because you then pop up some decent aerials.

However I do know they solved the "100 mile R/T problem" during WWII and the Wireless Set No.12HP (high power) was reckoned to be the first one to do this. It was replaced by the WS53 late in WWII. These sets are very like the T1509 in that they have a couple of 813 valves (or similar) in the PA, modulated by another pair of 813s in the high level modulator.

The engineering in all these sets has to be seen to be believed. Its very high quality. Most of them have been broken up in past years for a ready source of top quality components, so you don't see many of them still together in one piece.

They can produce top quality AM signals as well. Indeed some have even been turned into ad-hoc broadcasting stations when needed (those that go down as far as medium wave that is). I know that's true of the WS53 in wartime France, and the BBC reportedly had an ET-4336 in service up at their Woofferton site (and may still have) for some kind of local radio on MW. I had the ET-4336 out of the retired Cold War bunker in Birmingham, which was apparently kept there to broadcast to the local population should the end of the world actually occur......


Richard

[Alistair D]

Thanks for that Richard. Most informative.

Al

[Sean Williams]

Seems the PRO holds a few documents related to the T1509 - I hope to make a visit there early next week.

In the main they relate to the prototype and design, along with tropicalisation trials - I will see what the documents hold, and attempt to gain permission to publish extracts from them.

Well, assuming the information is of interest to others.....

Sean

[trh01uk]

Sean,

its worth taking a camera along to photo docs, cos they charge a ridiculous amount for photocopying.

Unless you are literally proposing to put the docs into a magazine article, I wouldn't use the word "publish" with them. Every PRO doc I have had has hard large notices saying it wasn't to be published, copied....etc. It will only ring alarm bells and/or encourage them to extract large amounts of cash. If you say you want to share the docs with a few other researchers (which is what I presume you intend) then they will probably be OK with that.

I for one will be most interested to see what you turn up.


Richard

[ms660]

Originally Posted by trh01uk

Sean,

its worth taking a camera along to photo docs, cos they charge a ridiculous amount for photocopying.

Unless you are literally proposing to put the docs into a magazine article, I wouldn't use the word "publish" with them. Every PRO doc I have had has hard large notices saying it wasn't to be published, copied....etc. It will only ring alarm bells and/or encourage them to extract large amounts of cash. If you say you want to share the docs with a few other researchers (which is what I presume you intend) then they will probably be OK with that.

I for one will be most interested to see what you turn up.


Richard

A very valid point Richard, I nearly fell foul of PRO/CRO copywright on more than one occasion. On the other point I think most of us would be interested to see what Sean turns up, many of us are are familiar with our old bits of kit from a practical point but there are still big holes in a historical context etc all very interesting and needs recording.

Lawrence.