MW.E.c. and E.U. a2 for operation

[17thairborne]

I have a good friend in town has encouraged me to pursue maturer radio operation as a hobby. It has taken me a year to warm up to the idea, as it was not in line with my military collecting interest.

Recently I came upon a nice old German WW2 radio. Coupled with my collecting of HG uniforms for which I had a set up of a panzer man in an IT field made camo wrap with headset and throat mike, I was bitten.

Below are the components that will be arriving within the next two weeks. I will begin reporting on the progress using the threads in the WAF commo section, help from my friend in town and hopefully encouragement and advise from those who frequent the WAF.

Here are the two pieces that started it all. I should construct some sort of metal rack next to the display to show the radio and umformer.

[17thairborne]

Umformer and cable array.

[17thairborne]

Schematic (Schaltbild) for the Mw.E.c

[17thairborne]

The Mw.E.c uses 9 tubes of the type RV12P200. Here are the Technical Data Sheets for the tubes.

Page 1 and 2

[17thairborne]

Page 3 and 4

[17thairborne]

Here is the tube test card for use on the RP 4/3 test device. I will have to do some research to find the exact dimension of the cards unless someone knows.

[17thairborne]

I found a bit on the history of the Mw. E.c here:

http://www.radiomuseum.org/forumdata...2005_129_2.pdf

" Die meisten Mw.E.c sind in Erfurt gebaut worden: die ersten 156 Geräte bis März 1942, nachweislich 10800 bis 31.3.1944, bis Kriegsende vermutlich etwa 16000. 1943 ist eine weitere Firma in die Fertigung eingestiegen, die bis Kriegsende noch etwa weitere 10000 Mw.E.c hergestellt hat (Gerätenummern unter 10600). Es wird interessant sein herauszufinden, welche Firma das gewesen ist'"

Rough translation:

Most of the Mw.E.c were built in Erfurt: the first 156 devices up to March 1942, verifiably 10,800 devices up to 31 March 1944 and up to the end of the war approximately 16,000. In 1943, an additional company climbed aboard, which produced another 10,000 Mw.E.c (Device serial numbers under 10,600). It will be interesting to determine which company that was.

Here is the data tag from the inbound radio indicating 1943 production. It will be fun to see if the interior shows the company of manufacture.

[17thairborne]

From the same article it mentions:

"Fakt ist, daß die Druckschrift D 968/2 „Der Mittelwellenempfänger c“ vom
29.11.41 in Schaltbild und Montageplan diese erste Ausführung mit Bandfilter
-eingang und mit den alten Quarzen in Keramikfassung zeigt, obwohl zu dieser Zeit nur noch Mw.E.c mit dem gelben Strich, also „formgeändert“ ohne Band-filtereingang und mit Vakuum-Quarzen hergestellt worden sind."

Translation:

The fact is that the instruction manual, D 968/2 "The Medium Wave Receiver c", of 29 Nov 1941, depicts in the schematic and the assembly plan, the first models with a band filter and the old ceramic crystals, even though at this time only modified radios without BFO and with vacuum tubes were being delivered, namely those Mw.E.c with the yellow stripe.

I see my 1943 produced radio has the yellow stripe (black arrow in image) indicating is is the modified version with vacuum tubes instead of ceramic crystals.

[17thairborne]

I am still awaiting the arrival of my radio, but the manual is here. I began a translation for my friend, and will post some of the basic portions of the manual here. I found a great site to help with my technical German.

http://www.welt-der-alten-radios.de/...eutsch-27.html


I. Overview and Frequency Range

The Meduim wave receiver "c" is a super heterodyne receiver with an HF amplifier stage, a mixing stage, an initial heterodyne stage, two amplification stages, a combined demodulator/LF amplification stage, a push-pull amplifier and a secondary heterodyne stage.

It serves for the reception of modulated transmitters (Operating Mode "Tn") and unmodulated transmitters (operating mode "Tg" or "Tg with filtered audio)

The accompanying transmitter has the designation "30 W.S.a or 80 W.S.a."

Frequency range: 830 kHz to 3,000 kHz (361...100m)

Designation: MW.E.c.


II. Technical Structure


A. External structure.

The receiver is enclosed with a dust and watertight sheet metal protective case and is annotated with the caption:

MW.E.c

The cover of the case is held tight with two dszuz fasteners.
Various operating dials and buttons are arranged on the face plate.

(I've omitted the various dial descriptions at this point)


B. Current Sources.

The operating voltage for the filament of the tubes is 12v, and for the anodes, 130 v.

As a power source the following are provided:
A 12v accumulator (battery) which delivers the filament current for the receiver tubes. At the same time the current is transmitted via the transformer "E.U.a." to the switch for initiating anode current flow for the receiver.


C. Interior Structure.

On the rear of the core are the following self-contained components:

HF section (position a)

Tuning capacitor section (pos. b)

IF stage (pos. c)

Super heterodyne stages (pos. d)

LF amplification stage (pos. e)

)enough for now, translating is tiring business

[17thairborne]

continued

a) Simplified Schematic

HF Amplified Stage

The HF oscillations arrive at the antenna via the condenser (part no 190) and then through the receiver frequency antenna circuit which is composed of the coil (120), the tuning capacitor (121) and the coupling coil (123). The tuning capacitor (192) (matching) serves to balance the capacitor differences of different antennae.

From the tuning capacitor (123) the HF oscillations are inductively transmitted to the grid circuit of the first HF tube (14). This circuit consists of the coil (129) and the tuning capacitor (121b). The HF current flows through the capacitor (102) to the grid of the HF tube (14). In the anode circuit of this tube, which is composed of the coil (144) and the tuning capacitor (121d), the HF oscillations cross the grid circuit with increased strength.

The anode voltage is transmitted over this tube via the resister (32). Spurious HF oscillations in the anode circuit are dissipated via the capacitor (33) to ground.

The screen grid voltage is extracted from the anode voltage source via a voltage divider (25/26). Grounding of the HF screen grid is created via a capacitor (27). The tube (12) obtains its grid bias through the voltage drop of the cathode current in the resisters (66,68,71) and the potentiometer (72).

The tubes work with a self contained amplification control in the form of an additional varying grid bias that are tapped from the rectifying stage via a resister (96).

Mixer Stage

A new frequency is created in the mixing tube (16) from the mixing of the received frequency and the assistance frequency generated in the heterodyne. This is the Intermediate Frequency (IF). The previously amplified receiver frequency flows through a capacitor (105) to the grid of the mixing tube (15) while the oscillations created in the heterodyne flow through a coil (143c) to the cathode of tube (14). The current of the cathode flows through a resister (74) which is bridged over the assistance frequency by a condenser (75) and in this method collimates the grid bias current. The IF steps up in the anode circuit of this mixing tube (16) which then is delivered to the quartz filter circuit.

The source for the anode current flows over a resister (36) of the anode current and through the resister (34) of the screen grid current. The screen grid is tied to ground via the capacitor (35) of the HF. The resister (105) serves as the grid leak.

[Quatsch]

I suspect the removal of the adjustable regen/bfo control was a slight cost savings measure, but the removal of the xtal filter may have been due to crystals being very hard to come by in the latter Reich years. Knowing the usefulness of quartz crystals in the high performance radio/electronics of the period, the US actually tried to corner the market on quartz, buying all it could from across South America wich was the world's supplier of quartz for xtals, starving the rest of the world, just as intended.

[17thairborne]

I understand the printing of the manual I am translating was done before the modifications. I would like to correlate your comments when I get to the appropriate section. Thanks for adding your comments.

[17thairborne]

continued:

I. Super Heterodyne Stage

The auxiliary oscillations, which are used to create the IF, originate in tube (15) of the first super heterodyne stage. The auxiliary oscillations are generated with an inductive threshold switcher. The circuit, specified by the frequency, emanates from the coil (143a), the dial capacitor (121c), the fixed capacitor (140) and the alignment capacitor (141). The feedback current is directed to the heterodyne tube of the grid (15) via a coil (143b). The capacitors, (121a-d) are situated in synchronicity. The anode current is generated in tube (15) via a capacitor(31) to ground. The screen grid current is obtained from the audio source via a resister (28). The capacitor (29) connects this grid to ground.

Please keep in mind I have no background in electronics or radio repair, and it is difficult to translate some of the technical phrases. Some of my syntax and verb use may not sound correct to one well versed in this field.

I welcome any comments which might make this crystal clear (no pun intended)

[17thairborne]

...but the removal of the xtal filter may have been due to crystals being very hard to come by in the latter Reich years.

Is this the component that was removed? Three of them are listed in the manual, Item Nos. (155, 167, 176) One is 353 kHz and two are 352 kHz.

If that is correct it is a blessing as these seem to be hard components to find.

[17thairborne]

Continuing on p.5 of the manual.

IF Amplifier

The IF oscillations that originate in the mixing stage arrive at the first IF quartz filter. This consists of the oscillations from one quartz (167) and oscillations from two IF tuned circuits, which combine out of the capacitors (161 and 169) and the coils (165 and 168). By changing the mechanical synchronism of capacitors (161 and 169) the band width of the quartz filter can be changed.

These IF oscillations are directed into tube (18) and then into the subsequent similaraly constructed quartz filter. This consists of a quartz (176), a coil (175 and 179), as well as the variable capacitors (174and 180). Tube 18 receives its anode current across a resistor (61) and its screen grid current from the voltage divider (63, 65) from the audio current. Capacitors (62 and 64) deliver the HF to ground. The cathode current flows through resistors (65, 71) and the potentiometer (72) and creates the grid current via the passing current loss.

In the position "Tn" of the operations selector (39c) further amplification of the modulated IF oscillations are created in tube (19). This amplified oscillation are delivered to the third IF tuned circuit that is generated via a coil (184) and capacitor (183). In the position "Tg" and Tg with audio filter" the IF oscillations are carried over the 2nd heterodyne stage via a coil (153) to the cathode of tube (19) and is mixed therein with the IF oscillations, In that the frequency of the second heterodyne stage IF oscillation differs from the IF oscillations by 900Hz, the audible frequency of 900Hz can be heard in the subsequent demodulation stage.

Anode current and grid current for tube (19) are drawn from the anode current source via resister (57 or 59). The capacitors (58 and 60) direct the IF oscillations to ground. The grid current is created through the current loss of the cathode from resistors (75 and 77). This tube works with an automatic amplifier control in the form of a self variation of the grid bias, that is taken from resistor (96) and in the demodulation stage.