E-622: Lorenz Eo 509 / I
E-622, All wave TRF receiver Lorenz EO 509 / I; developed and produced by C. Lorenz Aktiengesellschaft, Berlin - Tempelhof.
In the first six high power wireless stations G1,5K, a Lorenz EO 509 / I all-wave receiver was used as main receiver. Later, the Lorenz „bread crate“ receiver considered as a poor performer was replaced by the more modern superhet receiver E41 from Zellweger, Uster.
- Frequency range: 15 kHz - 20 MHz in twelve ranges, turret tuner
- Analog dial, nonlinear
- Accumulator / Batteries: Heaters voltage 4 - 6 V (from accumulators), plate voltage 100 - 150 V.
- 450 x 320 x 395 mm, 30 kg
The Lorenz EO 509 / I is a tuned radio frequency receiver with four tubes.
The „Bereichsschalter“, the band selector knob on the left side of the cabinet, drives a heavy gear turret tuner with twelve band ranges, it is visible after lifting the cover. The tuning knob „Abstimmung“ is located on the right side of the receiver front, the frequency dial is a log scale, it's small dial window is located on the right side of the cover. To determine the operation frequency, a calibration table on the lid assigns the frequencies to the log dial readings.
In the middle of the front panel, the main switch „Batterie ein - aus“ (on - off) and the headphone jacks are located. To the left you find the buttons for antenna tuning and „Korrektur“. With the rotary capacitor „correction“, both tuning circuits can be synchronised.
At the right of the main power switch and the headphone jacks, the regeneration control (increased regeneration does improve sensitivity and selectivity, it should be turned up just before the set starts oscillating), and the volume control.
On the left side of the receiver, the range selector, the connectors for the batteries, the antenna (short and long wire) and ground connecors, the antenna blocking circuit (an unwanted signal from a strong nearby transmitter can be phased out) and the control for the emergency detector are located.
After a RF amplifier stage (MF2) the signal is fed to the regenerative stage (MF2) where it is demodulated, then it is fed to two audio frequency amplifier stages (MF2; MF2) which deliver only power for headphone reception.
To receive unmodulated Morse transmissions (CW), the regeneration control is turned up, until the set starts to oscillate; then the unmodulated signal becomes audible.
A blocking circuit can be activated to eliminate an unwanted signal in the range 1000 - 3750 kHz; furthermore, a switchable 900 Hz audio filter lets pass a 900 Hz Morse code or Hell signal.
As found in other German (naval) receivers from the thirties, the EO 509 is equipped with a crystal detector for emergency reception in case of battery power failure.
The Lorenz EO 509 / I receiver is a typical example of a German naval receiver: due to the theoretical possibility of radiating the oscillator signal of a superheterodyne receiver over the receiving antenna, which could lead to detection of the receiver site, the German Navy used only TRF regenerative sets until the late 1930.
The technical characteristics (sensitivity and selectivity) of the Lorenz receiver did not match the performance of american superheterodyne receivers, so the Lorenz receiver was soon considered as obsolete and was replaced in the second series of the G1,5K station by the double conversion receiver Zellweger E41.