Mittelwellenempfänger c

This is a super compact high-end medium wave receiver with a "constant-k" crystal filter.
It was used in Panzer units for communication to higher level.

Frequency range
IF frequency
DC Power

830-1600, 1600-3000kHz
9x RV12P2000
352 kHz
+12V 1.2A, +150V 30mA

200 mm
313 mm
180 mm

Front view

Behind the front panel. Very precise mechanic design.

Inside the Mw.E.c. Most of the cover plates are here removed.
Upper right is the IF frequency constant K filter.
Lower right is the AF amplifier and BFO oscillator.
Mid sections is the frequency adjustment capacitor.
Left section is the RF amplifier, Oscillator and Mixer.

IF section with the Constant-k crystal filter

RF amplifier, Oscillator and Mixer.

Here we have the special 'constant-K' IF filter which allow a continuously variable
bandwidth from 100 Hz to 8 kHz. This type of filter was invented by Telefunken in 1936.

LA8AK’s Mw.E.c diagram

RF front end, Mixer, Oscillator, two stage constant-k crystal filter and BFO oscillator.

Audio detector (20), Audio power amplifier (21-22).

The audio detector is strange.
AGC voltage is generated on the anode over R96 and R97.

Here is LA8AK’s comments:
Mw.E.c detector. Pentode applied as duo-diode-triode, not widely known, but some reports
exists (G3VA technical topics, Radcom), and on an occasion 6AM6/EF91 was used by accident
as 6AT6/6AV6/EBC90/EBC91 and functioned properly, the "fault" was only discovered several years later.

This is the 353 KHz BFO crystal. It is similar to the 352 kHz IF filter crystals.

IF filter frequency response with the control adjusted to minimum bandwidth.

IF filter frequency response with the control adjusted to maximum bandwidth.

All tubes in the Mw.E.c is of the RV12P2000 type.

The Mw.E.c is now ready for communication on 80 meter ham band. I use this receiver both for SSB and CW.

Here is my Mw.E.c power. Input is 12 Volt DC. Output is 12 Volt DC for heating and 130 Volt DC for anode.

This is my 80 meter converter for the Mw.E.c. More info on:

The Mw.E.c’s performance on CW and SSB is very good.