Fu. H. E. d

(monitoring receiver)

This is a general-purpose, portable, up-to-date (for 1940) super-heterodyne receiver of die-cast light alloy and sheet aluminum elaborately designed. It operates on an intermediate frequency of 3 MHz and consists of two HF amplification stages, frequency changer, separate oscillator, three IF stages, amplifying grid detector, output tube and heterodyne oscillator. A rotating turret carries the HF and oscillator tank circuits - 4 sets of 4 tank circuits each; inductance adjustment is by threaded iron cores in the antenna and HF plate coils and by a copper slug in the oscillator coils; parallel trimming is by variable ceramic capacitors and oscillator padding by fixed tubular ceramics.

Circuits are tuned by a 4-gang variable capacitor of die-cast construction with ball bearings and ceramic insulation. The heterodyne oscillator is controlled by a three-position switch - one for "off" and other two giving notes of 1000 KHz below and 1000 KHz above the null point. A 900 KHz filter that permits CW signals to be received, in spite of interference, consists of a tuning iron core choke in the 2nd detector plate circuit that can be inserted by switch "Tonsieb".

AVC is extremely effective, rise out of output being 2 DB between 5 microvolts and 50 millivolts. The first IF coupling comprises a pair of tuned circuits coupled through a quartz crystal and a reactive link having common inductance and a small capacitance. A small 2-gang variable capacitor de-tunes the two circuits in opposite directions. The receiver has ample total gain; when tested on bandwidth of 10 KHz using a dummy load of 100 Ohms, the modulated input (30% modulated) for signal/noise ratio or 20 DB varied between 10 and 16 microvolts. The corresponding figure on a narrow bandwidth and without the filter is 4 to 7 microvolts or approximately 1 microvolt on CW

Intermediate frequency is 3.0 MHz.

Translated from "Die deutschen Funkpeil- und -Horch-Verfahren bis 1945" by Fritz Trenkle

After the arrival of the new Wehrmacht vacuum tubes in 1937/38, the Heer and Luftwaffe issued specifications for new monitoring receivers that were battery-operated, and which had the same control panel/face-plate construction. Telefunken and Lorenz submitted prototypes for competitive bidding, and the following were chosen for production:

Bezeichnung Deckname Frequenzbereich Lieferer Röhren Muster anlieferung
Fu H.E.a "Horst A" 75 - 875 kHz Telefunken 10x RV2P800 Mai 1939
Fu H.E.b "Horst B" 875 - 3750 kHz Lorenz 11x RV2P800 Mai 1939
Fu H.E.c "Horst C" 3,75 - 25,8 MHz Telefunken 10x RV2P800 Okt. 1939
Fu H.E.d "Horst D" 25,5 - 61,0 MHz Telefunken 12x RV2P800 Okt. 1939
Fu H.E.e "Horst E" 60 - 151 MHz Lorenz 13x RV2,4P700 Mitte 1940
Fu H.E.f "Horst F" 145 - 305 MHz Löwe-Opta (E=Lor.) 4 Eichelröhren + 8x MF 6 (1939)/1943

These devices were (as their immediate predecessors) directly calibrated and came with large circular frequency scales with a 270° radius. The scales were calibrated on their front side in "kHz" and/or "MHz" and calibrated in meters "m" on their back side. Both modes could be used in the field depending on the application. The frequency stability overall was uniformly maintained at 3x10-4 (for temperature fluctuations of -20° to +40° C, changes in operating voltage, etc.,). The manuals for the Fu H.E.a through Fu H.E.d receivers unfortunately do not have any mention of sensitivity or selectivity, etc., Despite this, one can easily say that in the years of 1939/40 (together with the heavy receivers Lw.E.a and Kw.E.a) these were the most cutting edge receivers in the world. However, their cost was about three times greater than that of the Torn.E.b.

The LF receiver Fu. H.E.a possessed an HF pre-selector stage (with a single circuit) and two IF stages with adjustable quartz filters, a IF detector, an LF stage, a telegraphy (tone) heterodyne with two selectable quartz crystals and a special quartz-tunable calibration oscillator. The voltage for the AGC was obtained from the additional IF amplifier. The devices Fu H.E.b - d feature two HF stages with single circuits and three IF stages with adjustable quartz band-pass filter with single circuits respectively band filters before the detector. The telegraphy oscillator with two selectable quartz crystals may also be used as a calibrating oscillator. In the Fu H.E.d model, the first oscillator was designed in a push-pull configuration and served a secondary function as the LF stage. All of these devices used the RV2P800 vacuum tube and could engage a tone filter for A1 (telegraphy) operation. A second box of the same size contained the accumulator, batteries, headphones, spare tubes and other accessories.

By the start of the war, models "a" through "c" were manufactured in large numbers. The Fu H.E.d had not quite reached production at this time and was available in limited quantities. The Radio Surveillance Troops of the Army (Funk-Horch-Trupps des Heeres) were outfitted with these devices. These receivers were allocated based on the following detachment designations: "Fu.-Horch-Tr. a/b, Fu.Horch-Trupp c" etc., The equipment set "Fu 14 (EZ)" for receiving stations included around 10 Torn.E.b receivers and three heavy short wave receivers (Kw.E.a) each, and two monitoring receivers Fu H.E.a to Fu. H.E.c, and later 2x Fu H.E.d. There were also large receiving stations which were equipped with larger multiples of these devices and a variety of other devices (mentioned later).

The monitoring receiver models Fu. H.E.e and Fu H.E.f were only in development at the start of the war. These models were constructed such that behind the familiar control panel, the lower half of the receiver contained all the mechanics and electronics, while the upper half carried the accumulator, batteries, spare tubes, etc. The development of both devices became delayed until 1942/43 because the number of radio experts available for development that have not been recruited into the Wehrmacht was just enough to continue building existing models.

The Fu H.E.e (60-150 MHz) was manufactured by the Fa. Lorenz company and was equipped with 13 x RV2,4P700 vacuum tubes. It possessed two HF stages with single circuits and five IF stages with band filters and diode rectification (pentode configured as diode). The last band filter was switchable for the reception of frequency-modulated signals (presumably as an FM demodulator, this is unclear in the documentation). This receiver was known only in the lists of the Luftwaffe. For the sensitivity, (operating modes A2 and A3) 1 V output voltage (S/N 3:1 )was attained with 1-10µV input voltage. The half-width of the IF was 170 kHz, for tuning deviations of ±300 kHz produced a 20,000 increase in the input voltage to produce 1 Volt. The frequency stability of 3x10-4 is maintained through everything. A parallel model from Telefunken was configured as a double super-heterodyne with 14 x RV2,4P700 and there were 6 frequency ranges (instead of 4). More information is not available for this model.

The Fu H.E.f (145-305 MHz) was configured with the following vacuum tubes: in the input stages (2 HF stages and mixer) with 3 acorn tubes (Philips) 4676, in the local oscillator with a acorn triode 4675, in the other stages with each using an MF6 (forerunner of the RV2,4P700 but with 1,9 V operating voltage). For reasons of maintaining a constant pitch, unmodulated carrier for finding or receiving toneless telegraphy, a modulation of the first IF oscillator was performed with an audio frequency, instead of the usual Tg overlay. A small 10 unit production run of this device was made in 1942/43for the Heer and Luftwaffe. It is questionable if other small series of this device followed later (compare below).

Some of the monitoring receiver, especially several Fu H.E.c were later to be used in multi-receiving fax, radio teletype systems "MEFA IV" = "sawfish" modified electrically (lead out of control conduit) and mechanically (connector on the front panel for rack mounting).

There were plans to create receivers with the Fu H.E.g through "s", but they never got past the planning stage.

 
Specifications
 
YEAR INTRODUCED :
1939 October
   
MANUFACTURER: Telefunken
   
FREQUENCY RANGE:
(MHz) 24.28 - 61.9 in 4 bands

NUMBER OF CRYSTALS:
1

PRESET FREQUENCIES:
None

ANTENNA:

TUNING:
(MO OR CRYSTAL) MO. The tuning dial has a graduated scale calibrated to kilocycles whose color codes agree with those of the band switch.

SENSITIVITY:
High

SELECTIVITY:
Adequate - bandwidth variation of 1.2 to 10 KHz for 6 DB of attenuation.

POWER SOURCE:
Two-volt "A' battery and 90-volt "B" battery housed in a separate case. The set may be connected to the NA6 power supply. Power consumption with anode voltage of 90 is about 14.4 milliamperes; filament current at 2 volts is 2.04 amperes. (Batteries 2B38 or 2,4NC58, 90V Anodebatt.)

SIMILAR SETS

POWER OUTPUT:

TUBES (TYPE and NUMBER):

12 x RV 2 P 800 (pentodes)


USE:
For enemy intercept service, for security monitor service and for standby and information service on German frequencies. This receiver has been found hastily fitted into a Ju 88 which crashed in August 1940. It is also fitted with strap hooks and pad for protection of person carrying it. It is not intended to be carried long distances since it weighs 56 pounds.

TYPE OF SIGNAL:
CW, tone and voice.

RANGE: (MILES)

TO COMMUNICATE WITH:

TO REPLACE IN PART:  

 
TRANSPORTATION:
Pack, plane or vehicle
 

 

The receiver when I got it. Covered in 64 years of dirt.

 

 

After cleaning with warm water and sponge.

 

 

Manufacturer data.

 

 

Waffenamt stamp

 

 

Voltmeter.

 

 

Vacuum tube testing control.

 

 

Cover off. Very nice condition and construction.

 

 

Rear of the frequency range selector switch. Note the large ball bearing and the ceramic core. Also note the stamps. There is a reference to the "Elekr." or Electrum alloy used in construction and also the word "Temperiert" - Tempered.

 

 

More interesting stamps.

 

 

The two AF tubes and detector tube.

 

 

Right side of the Fu.H.E.d. The coil turret, power connector and headphone jacks can be seen. The power connection data is also given.

 

 

Close up of the coil turret.

 

 

Close up of the power and headphone connector.

 

 

Left side of the receiver.

 

 

Close up of the lower section showing the local oscillator tube (covered and shielded) and the three IF amplifier tubes.

 

 

The middle section of the left side. Two HF stage tubes, and the heterodyne tubes can be seen here. I have to check the schematic to see why tube #4 is there.

 

 

A large electrolytic capacitor is at the top of the left side.

 

 

The receiver from the top.

 

 

The coil turret contact paddles and their ceramic base.

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