All wave receiver Lorenz EO 509 / I
C. Lorenz Aktiengesellschaft, Berlin - Tempelhof

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Swiss Army Communication Sets
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Army Receiving Sets
Exxx Designations
E-600 / Autophon E39
E-601 / Zellweger E41
E-602 / Autophon E44
E-603 / Autophon E45
E-604 / Autophon E46
E-606 / Velectra
E-610 / National HRO
E-622 / Lorenz EO 509/I
E-625 / National HRO
E-626 / Zenith H500
E-627 / Autophon
E-628 / Autophon
E-629 / Collins 51J-4
E-635 / Philips BX-925A
E-638 / Telefunken E108
E-639 / Telefunken E104
E-640 / Telefunken E127
E-643 / Collins 51S-1
E-645 / Siemens E311
E-646 / Zellweger
E-649 / Watkins-J.
E-655 / Racal
E-657 / Telefunken
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überarbeitet am 3.1.2015

In the first six high power stations G1,5K - the "Big 1,5 KW Short Wave Stations" - a Lorenz EO 509/I all wave receiver has been used as main receiver. In the later stations with serial numbers above No. 15, the Lorenz "bread box" has been replaced by the much more modern superhet receiver E41 from Zellweger, Uster.

TRF receiver with regeneration, crystal detector for emergency operation

Analog dial


15 kHz - 20 MHz

Sensitivity 2 - 20 uV



The Lorenz EO 509/I is a regenerative TRF (tuned radio frequency) receiver, it has two tuned HF circuits and four valves.
The twelve band segments of the EO 509/I can be switched by rotating a heavy coil turret, the impressive coil arrangement can be seen, when the cover of the receiver ist lifted off. It has only a logging frequency dial with the numbers indicated in a small window at the right end of the cover, a frequency chart on the receiver cover helps attributing the frequencies to the readings of the logging dial.
A cariable capacitor "Korrektur" (stands for frequency "Correction") is used to bring the two HF circuits in tune.

block schematic
The signal from the antenna socket is amplified in a RF amplifier stage (MF 2) followed by the reaction stage (Audion, operated by control "Rückkopplung" (regeneration)) (valve MF 2) for demodulation. After two AF amplifier stages (valves MF 2, MF 2), the audio signal is fed to the headphone sockets, the AF output power is not sufficient to drive a speaker. For the reception of morse code transmissions (CW), the regeneration stage is brought into oscillation (control "Rückkopplung") and the emerging howling noise makes the unmodulated morse code signals audible.
A RF blocking circuit is provided to eliminate an interfering radio frequency signal in the 1000 - 3750 kHz range, in addition to that, a selective 900 Hz AF filter ("Ton Selektion") can be activated, this will only let pass morse code or Hell radioteletype signals.

Like most of the German marine receivers, this All Wave receiver is still a regenerative TRF set on a very high standard - the German navy stepped back from using superhet receivers on their ships for many years, because of a fear, that their oscillator signal could be use to trace the ship's position. And like some other German made marine receivers from the thirties, also the EO509/I comes equipped with a crystal detector for emergence reception in case of a power failure onboard the ship.
Lorenz E509/I offen Kristalldetektor zum Notempfang

As the Lorenz EO509/I is still a regenerative set, it's sensitivity and selectivity has been considered as quite poor compared to the reception quality of the superhet receivers, a design which was preferred from American receiver developers - even by the Swiss Army signalmen.
As this Lorenz receiver was considered as technically outdated, a poor performer and without sufficient stability for Hell radioteletype operation by the Swiss Army, it was replaced by the double conversion superhet E41 (All Wave Receiver Uster) made by Zellweger, Uster, in the second badge of wireless stations G1,5K.

© Martin Boesch 2.1.2015