Kw.E.a - HF
(manufactured from 1938/39++)
Front view differences with Lw.E.a
Links to reference pages:
e11. Receiver's Intermediate Frequency List
e12. Data for German communication receivers
e86 Thermionic Valves (tubes)
22r SSB for KwEa
22c LwEa and T8PL39
22h) Funkhorchempfänger 'c' und 'u', Fu.H.Ec and Fu.H.E.u
28b EWb and EWc DC-DC inverters
28c NA6, NA6a Netzanschlussgerät für KwEa und LwEa
E96 Netzgeräte für KwEa, LwEa, Torn.E.b, FuHEc, FuHEu
Technical articles under preparation (received from PA0SE Dick Rollema):
10a Introduction to German World War II Radio Equipment
12a. German World War II Radio Equipment - Köln E52 receiver - part 1 (PA0SE Dick Rolema)
12b. German World War II Radio Equipment - Köln E52 receiver - part 2 (PA0SE Dick Rolema)
12c. Lorenz Shortwave Receiver Lo6K39a (Lo6L39), The ultimate TRF set [PA0SE]
12d. Telefunken World War II Superheterodyne Receiver Kw.E.a (Lw.E.a) [PA0SE]
10b. Telefunken World War II Universal TRF receiver Torn.E.b [PA0SE]
differences with Lw.E.a
More info for Kwea/E454Bs and LwEa/E440Bs
Circuit diagram for KwEa as pdf file is available here (tnx LA6TJA):
These additional scanned files from the handbook are available upon request:
pg 1-7 (2174kB), pg 8-19 (2175kB), pg 20-36 (2183kB), pg37-38 (268kB)
The receiver seen from above
The receiver seen from the rear (picture from the handbook)
Differences in IF-section between KwEa and LwEa
This receiver has 3 IF stages, and an extra AGC amplifier, while LwEa has only two IF stages and no AGC.
Optimizing the receiver or not (SSB):
The first thing to do when you have unscrewed the front and have done some possible repair*), is to rewire the
RF gain (Störhöhe) such that it operates independent for CW/SSB reception. This is more important if you don't
improve it for SSB in other way as mentioned below. The reason is that since the BFO injection is so weak you
must decrease the RF gain to avoid overloading the detector process, and you must increase the audio gain
by the same amount. It is not possible without this rewiring.
NOTE: It should be mentioned that neither any of my Kw.E.a's nor Lw.E.a have needed any sort of repair,
no capacitors have been found defective in any way. But this may not indicate that they are not bad in
any ways, they just work satisfactorily. Got the 2nd KwEa from LA1JC as a present in 1967, the first was purchased
from LA1II (later Permo) in 1963, and unfortunately sold in 1968..
See further SSB modification notes on page 22r
The AGC amplifier is in principle - very much the same circuit as for Collins 51-S. A standard voltage doubler is used with a voltage delay of +3,5V so that the AGC level increases faster when it reaches a certain level, but let weaker signal pass without attenuation. The Collins receiver doesn't have different time-constants for different modes, the modifications are shown on page b35, and the improvement was tremendous, and the Collins 51S was designed 20 years later than KwEa! Even BC-348 has different time constants for the different modes.
On board "308" one may choose between 0,1 and 2µF in Telegraphy mode, dependent on whether the receiver operates for "bewegl. - (= mobile)" or "stat. Betrieb (= stationary operation)", but it is a similary selector mentioned on the circuit diagram for E52 'Köln', see the next note below.
AGC measurements [frequency 2200kHz, Bandwidth pos.2, Vorkreise '1', Wavetek Model 3001, WG SPM-3 Pegelmesser (high impedance), AF load 4000 ohm].
RF gain turned up fully clockwise, AF gain adjusted to desired output level.
|RF level||Audio output level|
The RF gain control (Störhöhe) has no or little (less than
1dB) effect on AF level over the range for RF levels above 100mV
Background noise (for the AF gain setting): -14dBU. [AGC threshold at ca.18-20dB SINAD]
Blockdiagram showing which stages have AGC and which have MGC, from the above notes it seems that MGC has somewhat less than desired regulation, while AGC range is almost what is expected from a good communication receiver. Note that I have modified the receiver such that RF gain control is independent of audio level control setting, it is otherwise a problem to receive ssb signals.
The AGC amplifier for Collins 51S is functionally very similar to Kw.E.a
1) Antenna connection for
coax cable with LwEa and KwEa receivers.
2) Function selectors inside this receiver.
"221": It is possible to decide that BFO is activated when bandwidth positions 6-8 are chosen,
and the normal BFO switch is disabled (I don't know any expression for this selector).
"308" Bewegl./stat. Betrieb. The handbook doesn't tell, the circuit diagrams are almost
unreadable, but it seems to be a possibility to increase the AGC time constant with 2µF (304), and
according to the manual for Köln E52 to optimize the AGC (to short time-constant) for mobile operation
(the words refers to notes in the E52 handbook).
AGC/MGC switch modification for SSB operation.
see the notes for E52-series receivers
One should consider the bias circuit when building a power supply for the receiver, similar circuits for LwEa, FuHEc, FuHEu, TornEb
A simple way to connect a loadspeaker to a German receiver using loadspeaker transformer for 6BQ5/EL84 is shown on page.f16).
The result is quite good and satisfactory level even for SSB reception when RF gain has been rewired and BFO level increased.
Audio level meter for the receiver.
The receiver miss an S-meter, but you can compensate for it with an audio meter. It is fairly easy to make since the level is quite high and diode type is not critical, so I used OA70 type diode (but any germanium diode will do the job)
I .. 980-1610kHz .(Wht)
II 1560- 2550 .......(Red)
III 2470-4060 .......(Yel)
IV 3940- 6395 .......(Blu)
V.. 6205-10200...... (Grn)
Power supply: 2V accumulator and 90V anode battery or
Netzanschlussgerät NA6/NA6a, EU.d converter for 12V supply
Filament supply 2V 2,2A
Anode supply 90V 20...25mA
Measures: Height 274mm, width 692mm, depth 346mm, weight 42kg
Acessories; 2 headphones Dfh.a, 5 core cable w/connectors for supply voltages
Circuit: Valves: 11x RV2P800 as 2 RF amplifiers, mixer, 3 IF-amplifier, AGC IF amplifier and dry-diode detector (2x Sirutor 5b),
BFO/Calibrator (xtals 250/251,8kHz), Audion detector, Audio amplifier.
2 neon type Telefunken Te30
Te30 are neon tubes,
110V ignition and 80V stabilized voltage for RF input protection, see
page e86 .
One or two tuned circuits ahead of first RF amplifier, two tuned circuits
between first and second RF amplifier, and one between 2nd RF and mixer
plus one section for local oscillator.
3 double-tuned IF amplifier circuits for variable selectivity.
Reduced IF level to detector for CW (with BFO). Audio filter for
selectivity position 5-7(8). Position 7 and 8 have equal selectity
but BFO frequency is 251,8kHz for position 8.
Meter for anode currents and supply voltage.
Antenna: 200...500pF capacitance
Sensitivity for 1V RMS output into 4000 ohm, single input circuit, without AGC:
|Fall i utgangsspenning ved
Image rejection; at least 78dB (8000:1) @10MHz.
RF and AF gain controls are normally combined when AGC is on, but possible to
choose separate gain controls as without AGC with internal selector (switch).
RF gain is achieved by varying the gain on certain RF/IF valves with variable
screen grid voltage, but it is not the same valves as have AGC applied.
Intermediate Frequency filters.
It is three similar IF-stages on 250,9kHz. The circuit is drawn such that the similarities/differences with LwEa and T8PL39 (60kHz IF) can be seen. (next page).
see page 28c for power supply considerations using different equipment with NA6a
Current consumption: Filament current 2,2A, Anode current 20...25mA
Utførelse: Frontplate og chassis er støpt i silumin, kasse og deksel av pansertre
Ytre mål: Høyde ca 274mm, bredde ca 692mm, dybde ca 346mm
Vekt: 42kg (med rør)
Tilbehør: 2stk hodetelefoner Dfh.a og 1stk 5-leder kabel med 5-polige kontakter for strømforsyning
Constructing a tuning knob for KwEa or LwEa, see
KwEa mit Sichtpeilzusatz, und Prinzip des Sichtpeilanlage Fu Peil A70a
see: Die deutschen Funkpeil- und -Horch-Verfahren bis 1945, pg 99:
Aus der Anlage 351 entstand eine ortsfeste Version für die Luftwaffe mit einem speziell and das
Goniometer angepaßten Kw.E.a/apt. (2,5-6,4MHz) Super mit 11x RV2P800 und Vorstufe AF100)
mit der Bezeichnung 351bF = Fu Peil A 70, deren Anzeige jedoch noch nicht voll befriedigte.
Notes for LwEa, T8PL39 and NA6 (+ still some for KwEa) are found on on 22c,
and you will also find PA0SE Dick Rollema's notes on page 12d (not quite ready)
Aus der Anlage 351N entstand eine ortsfeste Version für die Luftwaffe mit einem speziell an das Goniometer angepaßtem KwEa/apt. (2,5-6,4MHz Super mit 11x RV2P800 und HF Vorstufe AF100) mit der Bezeichnung 351bF = FuPeil A70, deren Anzeige jedoch auch noch nicht voll bedriedigte. Sie kam ab Anfang 1941 in wenigen Exemparen zum Einsatz, z.B. in Catania (Sizilien) zur Überwachung des allierten Flugverkehrs von und zur Insel Malta.
Fritz Trenkle: Die dt. Funkpeil- und -Horch-Verfahren bis 1945, S.99.
Correspondence: You may write in English or German, Danish or Swedish, but I will reply in English (or Norwegian)