History of the Reception Set R. 209 MkI

[trh01uk]

Split from this thread:-

https://www.vintage-radio.net/forum/...php?t=172406:-

And while we are looking at the R209 Mk.I its worth saying a few things about its history, which I think is interesting - and with a certain amount of mystery reaching back into WWII.

Some think the set is one of the "Larkspur" radios, simply because it has a similar "look", with its cast alloy case which is hermetically sealed - a big feature of the Larkspur radios like the C11, R210, C42, etc. However it was in fact designed late in WWII, and was quickly partnered with the WS53 transmitter as a replacement for the earlier R107. It was thus a "model" for the later sets, and incorporated new ideas, such as modular construction, and FM as new and better mode than AM at HF.

What's even more interesting about it is the set that the R209 itself was based on. If you look closely at its case, you may note four holes in square on the top side. Apparently unused and redundant. Those were for an aerial base for the earlier set, the WS42, and the R209 re-used its cast alloy case.

The WS42 itself was an extremely advanced set for its time, incorporating not just FM to its AM and CW modes, but also a sort of "mechanical synthesiser" which allowed the operator to dial up the frequency wanted in 10kHz steps. It also managed an output on CW of 10 watts, which compared to other sets produced during WWII, WS19, WS22 WS62 etc was an astonishing advance in such a small portable package. And that's apart from its hermetic sealing, its cast alloy rigid case, which became a model for the much later Larkspur series.

The mystery arises as to why a set like the WS42 was suddenly designed during WWII with a radically different "design philosophy" from the run of the mill WWII radios. WftW reveals that it was designed by SRDE - the government signals research body. But as the wartime records for SRDE have all been lost I am not sure where that snippet of info came from.

I did an interview with Walter Farrar G3ESP (now long dead) where he told me he worked for SRDE during WWII, and specifically on FM at HF, and he had some amusing tales to tell! He also did the work on evaluating the German sets captured during WWII to see what could be learnt from them. He didn't mention the WS42 at the time, but the mere fact that someone was looking at German kit - which heavily incorporates modular design, alloy castings, and so on - and which looks something like the WS42 and R209 - suggests to me that this "step change" in design philosophy (as shown by the WS42) was initiated by an exposure of SRDE designers to German radio equipment.

All mere speculation of course, just putting 2 and 2 together.......


Richard

[G6Tanuki]

I always wondered what the four cast-bosses-with-holes were for on the top of the R209 case.... somehow I imagined them to be the mounting for a miniature version of the WS19-style variometer antenna-tuner!

[dave walsh]

That's all very interesting, especially the war time development/production of 209's, seemingly an anomaly ahead of it's period and non-Larkspur I'd known that the 209 was a WW2 set but didn't come across one for years. I always used to say that surplus gear had a big time gap in terms of usage before it appeared on the market [eg the Stealth Fighter]. A Wireless Museum article seems to date the [subsequent] R210 RX as being manufactured during a period of Company takeovers at the old RGD Factory in Bridgnorth, between 1952 and 1964!

When a batch of 210's were released in the early 1990's, accompanied by a detailed series of articles in Short Wave Magazine, it was suggested that they would have been in operation during the 1970's or earlier. Technically impressive, even then, there were three ways of setting up a PSU but one was considerably easier than the others. John Casewell started a thread about them recently.
[R210 Larkspur receiver 6/8/20]

Dave W

[G6Tanuki]

The British Military are rather well-known for stretching the lifespan of their equipments: I was in the Army Cadets and then the TA in the 70s and 80s, OK, us 'weekend warriors' generally got the full-time-Army's cast-offs but I remember talking to some of our US equivalents on an exercise in Germany sometime around 1977 and they were rather amused that we were still using VFO-tuned Larkspur (and pre-Larkspur: I loved my C12!] AM stuff on HF: they'd recently been issued with rather nice Harris fully-synthesized SSB kit.

R209s featured quite frequently in the early-1960s surplus ads in Practical Wireless - at a time when _proper_ Larkspur stuff was still very much in service. I was told that one of the intended roles of the 209 was that its "IF Out" socket would be connected to a RTTY or Radio-Fax decoder. Whether this ever happened I couldn't tell.

I've got two Mk.II R209s here - one has a plate:

ZA41971 MPF S.N 2021

the other is

ZA41981 M.E.L./R/2647

They both work remarkably well for their era: I've replaced loads of the aluminium-cased-waxies in the IF modules and the similarly-suspect black-rubber-sleeved caps that decouple the individual heater-dropper resistors. I've also replaced [in an easily-reversible way] the vibrators with a 2-transistor 'Royer' blocking-oscillator, which both reduces DC-supply load and cuts out a lot of the vibrator-frequency 'warble' when trying to resolve SSB on 14MHz.

[dave walsh]

Interesting again Tanuki. i will dig my 209 out [if i ever get back North and check the serial No on that one!

Dave

[trh01uk]

Originally Posted by G6Tanuki

R209s featured quite frequently in the early-1960s surplus ads in Practical Wireless - at a time when _proper_ Larkspur stuff was still very much in service. I was told that one of the intended roles of the 209 was that its "IF Out" socket would be connected to a RTTY or Radio-Fax decoder. Whether this ever happened I couldn't tell.

Well, somewhere I have a document showing the R209 was connected up to a WS53 - that monster transmitter with 2 x 813 in the PA - to form a RTTY link. I think that would date back to the late 40s and 50s.

The R209 replaced the R107 as a partner for the WS53, and I suspect it was precisely the availability of that IF output that forced the change. The R107 doesn't have that facility of course.

What the R107 does have - which the R209 does not - is a muting system. I have never understood how the R209 is supposed to be muted when the system is on transmit?

Richard

[trh01uk]

Also of interest is the fact the R209 is one of the earliest sets to include FM at HF. The earlier set is of course the WS42, and although 1,000 of these were made (according to WftW) I think nearly all went off to Burma or similar where its hermetic sealing could be used (and no doubt) tested in anger. None seems to have come back.

Walter Farrar told me an amusing story about how FM got introduced into the Army. He was on the team that did the very early experimental work on this mode during WWII while he worked for SRDE as a young graduate. He said they got the kit (sorry no idea what this was) together and laid a demo on for the Army "top brass". The trouble was that FM was so vastly superior to the AM systems they compared it with, that the Army top bods were convinced that it was a spoof, a con, just to get more money for further development work!!

Obviously they got over that one, as FM (or PM) became an additional mode on at least the following sets: WS42, R209, C13, A13, A14 - the latter sets belonging to the later Larkspur era. There was clearly ambivalence about FM though - as the R209 went from Mk.I to Mk.II with some sort of "downgrading" of the FM circuitry - I haven't studied the details to know precisely what they did.

I suspect the problem was that there were no FM transmitters available at the time to pair up with the R209 Mk.I, and possibly squaddies were switching to FM when working AM stations and getting duff results (squelch in VHF sets seems to have been removed for a while for similar reasons). The R209 was of course designed when the WS42 would have been the latest and greatest thing, so of course it had to have FM to keep up with that set. The WS42 got cancelled around 1946, when money was in very short supply, and the WS62 was bought instead, as no doubt a very much cheaper, and significantly poorer replacement.


Richard

[Stockden]

Originally Posted by trh01uk

Well, somewhere I have a document showing the R209 was connected up to a WS53 - that monster transmitter with 2 x 813 in the PA - to form a RTTY link. I think that would date back to the late 40s and 50s.

The R209 replaced the R107 as a partner for the WS53, and I suspect it was precisely the availability of that IF output that forced the change. The R107 doesn't have that facility of course.

While that's entirely true it seems that some R107 (and some AR88D) were modified for use on Carrier Shift Telegraphy with the WS53.

Originally Posted by trh01uk

What the R107 does have - which the R209 does not - is a muting system. I have never understood how the R209 is supposed to be muted when the system is on transmit?

It used to puzzle me too but I eventually found the answer in the Royal Signals Training Notes for the WS53. In essence the receiver wasn't muted at all (even with the R107). Instead the aerial was disconnected from the receiver and the receiver input shorted, all done by relays of course.

It's also worth bearing in mind that in some roles the R209 would have been used as a remote receiver, probably some distance from the transmitter, and thus muting would not have been required.

Hugh

[Stockden]

Originally Posted by G6Tanuki

I was told that one of the intended roles of the 209 was that its "IF Out" socket would be connected to a RTTY or Radio-Fax decoder. Whether this ever happened I couldn't tell.

As Richard has explained in his post, it was indeed used with the WS53 on RTTY, at least until it was replaced in that role by SR D11/R234.

I know that the R209 was also used by Royal Artillery units for the reception of Met broadcasts. I'd always assumed that these were voice or CW but it's possible that these were actually sent as RTTY/CFS. I'll have a dig around and see if I can prove or disprove that.

Hugh

[Keith]

It seems incongruous to me that the massive WS53 with it's 2x813 modulated by 2x813 would have been paired up with a receiver using battery valves! I wouldn't have thought that just shorting the aerial would have been enough to save the operators ears...

[G6Tanuki]

I _can_ see the logic of it - particularly if you're holed-up in a wood somewhere for a few days and having to start an engine to recharge your lead-acids would draw undue attention. Being able to run your receiver for 4 or 5 days from a single 110AH standard 12V battery would be a good thing.

[The usual Military charge-management model assumes a 9:1 receive:transmit ratio]

And as to "saving the operator's ears", if the listener was actually a RTTY-decoder coupled to the IF_Out port, it wouldn't be a problem.

[Radio Wrangler]

The battery consumption of a teleprinter and terminal unit would exceed that of the receiver, and the noise might rival a generator!
Probably low profile battery operation would default to CW.

David

[G6Tanuki]

The late-40s vintage ITT_Creed RTTY gear I worked with [in the 70s] shut-down the motor when the thing wasn't actually receiving a message. Convention was to send a line of BEL characters at the start of a message to give the hardware a time to spin-up [and to wake-up the inevitably-sleeping printer-custodian].

I wonder what TU the R209's IF-Out was intended to feed?

[trh01uk]

Originally Posted by Keith

It seems incongruous to me that the massive WS53 with it's 2x813 modulated by 2x813 would have been paired up with a receiver using battery valves! I wouldn't have thought that just shorting the aerial would have been enough to save the operators ears...

Just had a further dig into the Trade Training Notes for the WS53. If you look at Fig.20 (after page 25) it shows a "relay D" inside the Remote Control Unit 'H', and one contact is used to short out the headphones when the "SEND" switch on the remote control is activated. At least that's what the text on page 26 says - not what the diagram shows (Trade training notes are rarely accurate).

A recourse to the schematic of the H1 remote control, shows relay contact D2 actually disconnects the receive audio from the headphones which are plugged into that remote control.

So that's probably the answer here - that a remote control unit would be used typically - even if its only the other side of the lorry from the WS53. Again to be absolutely precise, the Remote Control Unit 'H' seems to have been replaced by an anonymous "Control Unit" shown in the vehicle diagram in Wireless for the Warrior, page WS53-36. What that control unit does precisely is not spelt out, but certainly the R209 audio output is fed into it.

So we might conclude some concern was taken about the operator's ears, but its lost in a myriad of detail about how the sets were worked into larger systems.


Richard

[trh01uk]

Originally Posted by G6Tanuki

The late-40s vintage ITT_Creed RTTY gear I worked with [in the 70s] shut-down the motor when the thing wasn't actually receiving a message. Convention was to send a line of BEL characters at the start of a message to give the hardware a time to spin-up [and to wake-up the inevitably-sleeping printer-custodian].

I wonder what TU the R209's IF-Out was intended to feed?

"TU" = "Teleprinter Unit" I presume? I had a quick look in the WS53 chapter of WftW, thinking that it would likely provide the definitive answer. It doesn't. It refers to something known as "Receiver Adapter Field CFS", which had a separate power unit known as "Supply Unit Rectifier DC/AC No.3". There's a pic of an installation in a 1-ton truck showing a couple of teleprinters, but I am not expert enough on such things to recognise them. That's probably a question for another thread.

What I did note though was that both the WS53 and R209 (it mentions Mk.2, but it probably applies to Mk.1 also) needed to be modified for CFS operation (this also applies to the R107 and AR-88 in fact as mods are shown for all these receivers). The WS53 training notes include details of these mods. It also includes a complete schematic of the CFS Adapter by the way. I can't see an explanation as to why an R209, which has an IF output anyway, would need further mods.....


Richard

[trh01uk]

And sorry, if you were literally asking which "teleprinter" was used, I can't see a reference to a specific type. But my guess is going to be the Creed 7B, or one of that family, since it was around from the 1930s onwards I believe.



Richard

[G6Tanuki]

"TU" = "Terminal Unit" - the box that takes an IF or AF RTTY signal from the receiver and converts it into an appropriate [typically +/- 80V, or 20-Milliamp current-loop] signal to drive the teleprinter.

"Properly" demodulating RTTY signals seems complex at first: if your input is an audio signal from a classic detector as you'd expect to use for listening to AM/FM/SSB signals you're really hamstrung and results will rarely be optimal.
Tapping the IF, down-converting to something like 15KHz, and _then_ separating the high- and low-tones with a pair of discriminators was the way-to-do-it; it gave you the ability to implement a 'local AFC' on the 465KHz-to-15KHz local-conversion oscillator, for a start. That was important if your receiver's HF local-oscillator was free-running!

[A deep discussion of DC-restorers and "Computers of Average Transients" to deal with the origin-shift when presented with repeat-patterns of 0s and 1s is inappropriate here]

[Radio Wrangler]

A whole new thread, as they say.

An advantage of an IF output to a TU is that it could include added narrow filtering shaped to optimise things for the two tones of the FSK

David

[trh01uk]

Noting this thread is strictly about the R209 Mk.I, its worth noting that this first version of the set did not have the IF output facility - despite the discussion above of the use of that facility for RTTY. There is a picture of the Mk.I set at: https://www.radiomuseum.org/r/mil_gb..._set_r209.html

Lacking further info, I presume RTTY was only used with the R209 when the Mk.II version arrived.


Richard

So far I can't see any sign that the Mk.I set was modified for RTTY use,