German Aircraft Radios

W.W.II German aircraft radios make very interesting radios to collect but unlike Japanese and American aircraft radios are not mounted on shock mounts but are mounted on one of the aircraft bulkheads. You need to find part of the actual aeroplane to mount these sets. One interesting fact is that they were one of the first, if not the first radios to make use of ribbon interconnecting cables, similar to those used in modern computers.

German aircraft radios are small compact and usually well constructed. Below is a brief listing of German aircraft sets, their components and other information of a general nature. These are sets that are known to be in private collections in the United States.

FuG 3
An airborne transmitter and receiver used in bombers. Has been found in Ju 52, FW 58, HE 114, DO 11, DO 17 E and F, Ar 66, Ar 96, W 33 and W 34 Set consists of :
E 2a Receiver
S 3a Transmitter
Power source: G 3 Air driven generator (None shown) and 2 - 90 volt dry cells.

FuG 7
An airborne transmitter and receiver used in fighters and dive bombers Prior to 1943 it was fitted in the ME 109, ME 109 F and FW 190. Still fitted in JU 87 and Hs 129
Principle components:
S 6a Transmitter
E 5a Receiver
Junction Box VK 5 A
Dynamotor U-LB/24

FuG 8

FuG 8

E10 K Receiver
E10 K Receiver, Front Panel	E10 K Receiver, Internal View

E10L Receiver, Front Panel

E10 L Receiver

FUG10 Complete Station	FuG 10 American Manufacturers have exhibited considerable interest in captured Axis equipment, wherever it has been shown. The following detailed description of the German FUG-l0 panel used in bomber and reconnaissance aircraft should, therefore, prove useful. The German FUG-l0 panel, or rack, contains two transmitters and two receivers. One transmitter and its companion receiver operate in the 300-600 kc hand. The other transmitter and its associated receiver operate in the 3000-6000 kc band. Both units employ CW and MCW operation. No voice communication is used. In addition, the following units are mounted on the panel: A remote-controlled direction-finder operating in the 100-1100 kc band, a blind-landing device operating in the 28-32 Mc band, and an inter-phone system which serves to supply communication to the aircraft crew as well as to interrupt the CW transmission for purposes of ground homing. Equipment is non-crystal controlled and relies on capacitance compensation for frequency satiability. Facilities are available for tuning a predetermined spot on a dial to a master-signal station which is undoubtedly maintained on frequency by crystal control.
FUG10 With 2 Units Removed
FUG10 ATU, Internal View	FuG 10 Antenna Remote Control Unit	FuG 10, Internal View

Transmitter Units SL and SK
These instruments each contain 3 type RLI2P 35 valves, which are indirectly-heated pentodes of 35 watts anode dissipation. One valve as master oscillator drives an output stage using two tubes in parallel. Master-oscillator and output circuit primary tuning is by iron cored variometer driven through backlash-compensated gearing from a single tuning control.

Electrically the high-frequency and medium-frequency transmitter units differ in detail only. Looking at a circuit diagram of the high-frequency unit SK, and it will be seen that the master oscillator is of the Colpitts type. Certain of the fixed condensers are of the high-negative coefficient ceramic type giving a considerable degree of temperature compensation. A small neutralising condenser is provided. The normal use of the transmitter is for c.w. communication, keying being carried out in he master oscillator and power-amplifier grid circuits. Special uses are radiotelephone transmission on the 5K unit with grid modulation, and impulse transmission on the SL unit.

The radio-telephony facility when provided requires an additional switch unit accessible to the wireless operator and a press-to-talk button for the pilot. The switch unit sets the output-stage grid bias to the correct value and provides modulating signals via the intercommunication amplifier. The pilot's radio-telephone requirements are catered for in later installations by a separate transmitter-receiver.

The impulse modulation feature was used to provide ground stations with a signal suitable for the taking of direction-finding bearings free from night error, but has been discontinued in the latest installations. The repetition frequency of this type of modulation is 300 impulses/sec and the impulse duration 500 micro sec. The generating oscillator and shaping output stage are incorporated in the intercommunication amplifier unit, the output being applied to transmitter power-amplifier grid circuit under the control of the main system switch. Power output is between 40 and 69 watts throughout both frequency bands on c.w.

The mechanical construction of the transmitter units is of light-alloy die castings are used for the several sub units, which are bolted together to form the complete transmitter. Plug-and-socket interconnections are used between the sub-units, and the captive fixing screws are identified by red paint. In both transmitter and receiver units the large-diameter dial revolves on a stub-axle and is calibrated in frequency, the scale subtending some 300 degrees. The hub of the dial carries four notched discs for the rapid selection of pre-set spot frequencies. Locking and unlocking of any one disc is accomplished by turning through 90 degrees the appropriate one of four coin slotted screws, visible on the front face of the dial hub. The spring-loaded stop-levers are interesting in that they are pivoted on an eccentric spindle which can be rotated through 180 degrees.

Receiver Units EL and EK
The receivers are of the super heterodyne type with one signal frequency amplifying stage. The EL unit, covering 300 to 600 kc/s, has an intermediate frequency of 140 kc/s with a total band width of l - 0 kc/s at 6 dB attenuation. The EK unit, covering 30 to 60 Mc/s, has an intermediate frequency of l4 Mc/s and a band width of 8 kc/s at 6 dB attenuation. The signal / noise ratio in each case approaches the theoretical limit determined by first tube and circuit noise. One micro volt (C.W.) applied through 50 ohms gives signal to noise ratios of 20 dB and 17 dB respectively, and the total gain at this input is such that the telephones receive 50 mw and 2.5 mw respectively. The second channel attenuation figures are 78 dB and 70 dB.

One type of tube, the Telefunken RV.12P 2000, is used throughout these receivers and also in the intercommunication amplifier and miscellaneous tube circuits. It is a small indirectly-heated pentode with a side-contact base and ring seal. The overall length is 5 cm, and the bulb diameter 2 cm. The moulded valve holder carries integral contact springs to make the top-cap grid connection and to earth via the metal frame. Input and output capacitance's are both approximately 4mmfd The mutual conductance is 2 -4 mA/volt, and the heater current 0.07A at 13 volts. The FuG 10 equipment uses a total of 25 tubes of this type.

A circuit diagram of the medium-frequency receiver EL 5. shows there is no automatic gain control, and the manual gain control operates on r.f. and 1st i.f. stages only. Radiotelephony reception is not provided. A separate local oscillator is used with a pentode frequency changer and anode - bend detector. The i.f. transformers have separately screened adjustable, iron-cored coils with fixed tubular ceramic condensers. Coupling is by capacitance connected between appropriate tapings to enable a standard type of variable trimmer to be used.

In the EK receiver the heterodyne oscillator is controlled by an on-off switch. The EL receiver differs in having the oscillator permanently on, and using a 3- position switch associated with two small ceramic condensers to give zero - beat or heterodynes 1000 c/s below or above intermediate frequency. This facilitates accurate inter-tuning of the transmitter to the receiver and ground station, and provides a means of eliminating interference from an adjacent channel. Mechanical design is on the same lines as the transmitter units with dimensions slightly smaller. Click-stop details are identical.

Two Aerial-Matching Units are used, one for the trailing aerial and one for the fixed, mounted as near to the fair lead and deck insulator as possible. Each unit contains two tapped variometer for tuning on h.f. and m.f. ranges, and iron-cored auto - transformers for matching aerial resistance to the 50-ohm feeders.

FuG 16

FuG 16 Z
Set is an airborne transceiver used in single seat fighter aircraft to proved VHF service to pilots, Tone for ground fixes and D/F homing on ground stations Principle components:
Transmitter, Receiver, Modulator in one case,* S 16 Z Tx, E 16 Z Rcvr,
NG 16 Z Modulator (Set appears complete, some paint flaking)
Dynamotor U 17
Antenna Matching unit AAG 16 Z
Modulator Unit MZ 16
Homing Unit ZVG 16
Indicator AFN - 2

Peil G 4
An airborne D/F receiver used in light bombers and single seat fighters. Fitted in Ju 87,a few ME 109Fs and ME 109 Gs, prior to the introduction of the FuG 16 Z Principle components:
Receiver E Z 4
Loop PRE 4
Dynamotor U 8
Junction Box VD 3
Tuning controls FBG 4
Indicator AFN 2

EbL 1 Receiver
This set is not listed in TME-11-227. Information on this set contained in magazine articles. It is a Lorenze type blind landing approach receiver, usually part of the FuG 10 system.

A word of caution on aircraft radios from one of Europe's foremost collectors, Arthur Bauer.
The German Air Force fitted onto the (aluminium) housings small aluminium strips which could carry explosives on the outer side of these apparatus. These explosives were linked then by a fuse (slow match cord) onto all apparatus which had occasionally to be destroyed. Once it was ignited a certain time delay was always maintained to allow evacuation of the crew.

I have once seen a tricky explosive which could be ignited electrically. It was fitted with a regular "bayonet" socket, though instead of two lock pins it used three of them. Probably to avoid being placed into the wrong place.

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