T 200 FK 39

My Italian friend Luca Fusari

Provided yesterday 13 April 2024

A US post-war report on their investigation

According the true performance of a

T200FK39a

Report: AD1202477

It was particularly designed for the use at places where space is limited, as is the case in submarines (U-Boote). This transmitter was used by the Kriegsmarine in their long distance u-boats . All boats sailing to the south Atlantic and/or Penang or Japan were, after say 1941, equipped with this transmitter type. In cooperation with the German Navy, Telefunken designed a remarkable stable transmitter (≈ 5 ppm, no quartz, though, employing a VFO!). It was German Navy practice, to designate the final two digits of a type-number(nomenclature) pointing to the year that a system was generally accepted by the Navy's ordnance organisation (thus here 1939)#. T stands for Telefunken* and 200 indicates that it provides 200 watt transmitting energy. F means 'Fern' or long distance, K (=Kurz) is indicating that it could operate > 7.5 MHz (when, for example, it would be type T200K39**, this will indicate that it could only transmit < 7.5 MHZ). There also might have existed a type T200FK41***, one may consider, that its basic design was similar to type ...39, though, with some changes(although, I have to admit this is not in all cases true). One may think of expanded frequency range or that like, maybe its frame was changed from originally 'die cast' to pressed steel, and/or utilizing some different valve types. However, T200FK39 was followed-up by type ...39a and ...39b and so forth. In these cases indicating more and more simplified versions. Such as, leaving out first the very elaborated motor-driven-tuning assistance (aid). #To some extent, also the Army used this system, the famous 'Luger parabellum pistol' was known as 'Pistole 08' which points to 1908, or 'Lausgerät 35' (line interception apparatus of 1935) or later xxxxx/41 → 1941. * 'L' would indicate C. Lorenz A.G. and 'Ha' points to Hagenuk. **Actually a not existing type, however, type T200L39 did exist and operated at long waves. There even exists a type T800FK39, which provide 800 watt transmitting power, its housing(also the power supply) is bigger and much heavier, but the controlling gear is comparable

Shown is the T 200 FK 39 transmitter, which is part of our collection (Exhibit 1995006T). Mod = the modulator and keying module; N is the rectifier section of the power supply unit; PA = the power amplifier (Endstufe) with driver stage; VFO = the variable frequency exciter and frequency multiplying stage (notice photo 8). The cover plate on the right-hand side of the transmitter had been removed and was replaced by a perspex (Plexiglas) cover, as to give an inside vision of its neat construction. The transmitter broad-size is only 26.5 cm! Remarkable is also, the use of flat horizontal meters, which where widely utilized in some German systems. All tunable dials were linked with mechanical counters. When, for instance, had to be tuned at a spot frequency, without actually operating the system, a table was provided with the exact digital numbers to be set (tuned at)

The power supply unit (PS). It is clear, that the transmitter is mounted on top of the power supply unit. The colour of the lower section, thus the power supply, carries its genuine paint, whereas the upper part, thus the T200KF39 transmitter, was repainted in post war times

I have to apologize firstly, for the inferior photo quality (will be replaced in due course), but under the circumstances was it not possible to make a better one. D = the driver tuning coil (Rollspule); E = the PA tuning coil, both 'D' and 'E' are tuned in concert. R = racks (=Zahnstangen) of which one is controlling the PA tuning and the lower rack R is linking transmitter and VFO/pre-driver stages; FC is the frequency calibrator; M is the tuning motor, which gets its guiding signal (rotation direction and halt) from a so-called "Kurvenscheibe". This system is based on Telefunken's patent DE720231 the inventor was C. Protze, application date 6.6.1939 (see: Patent DE). To get an impression of its mechanical complexity please notice Illustration 9

PA module, cover door opened. The RS 383 is the power amplifier valve, its construction is rather small sized compared to its power rating, which is 200 watt HF output at all ranges. Down we see two power valves in the driver stage, left is the clamp-tube which has to limit the driver level of the RS 383. Right is the driver valve, both types are RL12P50 (to regard some specs)(notice also diagram of photo 11). Interesting is, that all voltages and currents of all valves(stages) can be measured at test-plugs from outside, visible far down on photo 4. Also, the transmitted signal can directly be monitored. 'Frequenkontrolle' provides the audible beat-output of the frequency calibrator

The RS383 has been toppled outwards. The grey ring at the lower side of the RS383 is not its valve base, but belongs to the (toppled)valve socket. To release the RS383, the valve has to be rotated a few degrees and then being pulled outwards

This photo originates from the T 200 FK 39 manual. For a good picture, copy the illustration to your clipboard and paste it in word or another program

This photo with caption originates from a prior publication. It provides, however, a nice vision on how the VFO module was constructed. The visible ceramic ball-variometer was very robust and the rotating coil of special design. Its short circuit conductor was not a linear (cylindrical) metallic conductor, but at particular angles additional conductor rings linearize its frequency versus rotation(tuning) angle. It was based on Telefunken's patent DE 626597 invented by Kurlbaum, application date 26 June 1933 (for details look at Patent DE). The valves utilized were, in this module, 4 x REN904. The entire housing (say the housing around the variometers and components) was of very solid ceramic. Which was inside deposited with a massive copper layer for electrical screening, the cover-plate was of similar construction. The white tubes are sealed-off tropical-environment resisting capacitors.* The black box on the left-hand side (just inside the die cast frame) contains the microfilm glass scale. Similarly to Köln E 52 receiver and AS 60 transmitter. T200FK39 scale projection was more or less similar to the AS60 scale, though, had less brightness), the, for those days, highly accurate frequency reading was projected at a frosted glass-window (illustration 9 right from the second ball-variometer, somewhere in the centre of the drawing) * Similar VFO concept was already used in the standard u-boat transmitter type S 406 of 1936

Comments to the schematic diagram on page 21 (and photo 8) of the pdf manual abstract. To obtain better quality drawing, click on the illustration above

The principle of the VFO and (first)driver stage is rather special. The push-pull frequency oscillator (VFO) is followed by a so-called pus-push stage. This is a stage that get balanced signals at their grids g1 and the anodes being connected together. Such a circuit can only provide odd harmonics. In the case that even harmonics has to be considered, one grid (g1) is being blocked (B 3), so that the stage is acting now as a regular amplifier, and the blocked valve behaves as a neutrodyne-capacitance. Interesting also is - that Telefunken engineers knew already in the 1930s, that resistors directly connected onto grid in oscillator circuits is not appropriate and they utilized first a RF choke (A 10) and then a resistor; nowadays this is common knowledge. But it was then not practiced in US designed apparatus (being not acknowledged?)! See for additional information also: The significance of German electronic engineering in the 1930s

To obtain a good quality drawing, click on the illustration above, and a nice quality print will appear (in pdf). It is also possible to paste the drawing to your clipboard and then print it, for instance, in Word. I think, that only post war 'Collins' apparatus could match with such a complex mechanical design

For a better copy, click on the drawing of photo 10. One comment to its power supply unit. The high tension circuit is curious. It uses a swinging choke (this is not curious)followed by a series tuned choke-circuit parallel to its 1500 volt output (consisting of: C 2 in series with L 3)(I suggest, that it is tuned at 100 Hz*). However, it seems to be a good circuit design, as it still works, even today, very well (2007) * It is evident, that this could only function reliably, when C 2 is robust and not an electrolytic type

Principle schematic diagram of the driver and power stage of the T 200 FK 39 transmitter. Section 'K' is the antenna tuner. Click on the drawing above, to obtain good printer quality, or add it to your clipboard and paste it in word or that like

Showing to what this transmitter even today is capable, I attach a plot taken by Koos Fockens PA 0 KDF on 16 May 2010. He accurately measured frequency deviation between: Bastiaan PA3 FFZ, PA 0 KDF and my (PA 0 AOB) transmitting frequency. Our Hell-mode qso started, as in spring and summer time usually on 17.00 hour local time, at about 3577.8 kHz. My actual scale reading which is projected optically by means of a microfilm-scale on frosted-glass, is allowing only optical interpolation between 3577 and 3578 kHz, over a scale separation of about 1 to 2 mm. Scale deviation can be judged for say 100 Hz steps, more accuracy is becoming a matter of guess.

Koos set my frequency when the qso started at 0 Hz deviation. It is clear that in the starting-up phase my actual frequency moved about 60 Hz downwards and then stabilised within say 5 Hz, that is an astonishing good value for a free running frequency source (VFO) which is now more than 70 years old! I think this former submarine transmitter designed by Telefunken, is one of the best of its kind!