The Siemens E 309 has been developed to meet the needs of professional users in maritime and fixed point-to-point communications: the receiver is tuneable but there is also to possibility of crystal controlled fixed frequency operation.
The Siemens E 309 has the dimensions 52 x 36 x 41 cm and a weight of 38 kg, it comes with a rugges steel cabinet and two front panel handles / front panel protectors.
The receiver can be powered from 110, 125 or 220 Volt mains with the internal poer supply or from 12 or 24 V DC from an optional external converter.
The frequency dial is much smaller then the one found on the E-310, it is located in the middle of the frontpanel. Only a part of the rotating round dial is visible in the dial window, the edges of the respective bands are indicated at the sides of the dial window and the active dial is illuminated with an indicator light behind the fixed dial pointer.
At the left of the frequency dial, You find the grill of a switchable small monitor speaker, next to it the switch for the noise limiter. The rotary control below is the modes control with combined switch for long and short AGC time constants and the crystal calibrator. Further below, You find the bandswitch, the bands are indicated in a tiny window.
The round instrument at the right of the frequency dial can be used for measuring purposes and for frequency determination. Just below, You find the switch for tuneable and fixed frequency operation, the control "Quarzfrequenzkorrektur" acts as fine tuning control / clarifier when the receiver is in crystal controlled fixed frequency operation. The switch "Kontrollmessungen" sets the instrument to display the R.F. signal level (it will act as S meter), the audio level and to control several operation voltages of different tubes.
In the bottom row of controls, You find at the left hand the two contros for R.F. and A.F. gain, the main tuning knob with a mechanical lock, the control for operation frequency determination and the control for the variable I.F. bandwidth and the BFO note.
The mains switch and the headphones jacks are located at the bottom of the front panel.
Operating the E-309 is not complicated: Use the main switch to power on the receiver, A.F. gain should be turned up halfway, for AM reception, the modes switch should be set to "A3, automat. Regelung", the R.F. gain should be turned up fully clockwise.
Select the desired shortwave band with the bandswitch and use the main tuning knob to tunethe set to the desired frequency. The resolution of the main frequency dial is around +/- 10 kHz in the shortwave ranges. With some luck, You can identify the desired station from a spoken identification, the language used or the interval signal. For a better identification of a frequency, You can use the crystal calibrator and correct the main dial pointer position for correct readings.
As a peculiar feature, the E-309 is equipped with an electronic "Skalendehnung" / bandspread to tune the receiver exactly to a frequency between two 20 kHz marks. First, You have to tune the receiver to the 20 kHz dial mark below the desired frequency with the main tuning knob pulled out slightly. When You press in the main tuning knob, the tuning mechanism is mechanically coupled to a variable resistor. Now tune to the next 20 kHz dial mark, use the control "Vollausschlag bei Skalendehnung" (Full meter reading with band spread dial active) to adjust the meter reading (the meter must be set to "Skalendehnung" for this) to the 20 kHz mark on the instrument. When You tune back with the main tuning control, You can read the interpolated frequency in 1 kHz steps from the meter. After You pull out the main tuning knob again, the coupling between tuning mechanism and variable resistor / band spread dial is released and the radio returns to normal operation.
In case of interference from an adjacent channel, the I.F. bandwidth can be reduced until the interfering signal is mostly eliminated. This variable I.F. bandwidth circuitry is found rarely on commercial receivers.
The R.F. signal is fed from the long wire antenna connector via inductive coupling and two tuned R.F. circuits to the R.F. amplifier stage (EF93) and is mixed with the oscillator signal (ECC81) to the first intermediate frquency of 1326 kHz (EK90). After two I.F. amplifier stages (EF93, EF93) followed by two crystal filters - the variable I.F. bandwith control is realised by the two reciprocally tuned crystal filters - and another I.F. amplifier (EF93), the signal is demodulated in one system of the double diode EB91, the second diode is used as a serial diode in the noise limiter circuitry.
After the A.F. preamplifier (one system of the ECC81), in the final stage (EL90) an A.F. output power of two Watts is generated.
In the crstal oscillator (EF93), harmonics are generated every 100 kHz, another EF93 is used for the BFO for CW reception (A1).
A single sideband demodulator Funk 144 K 101 could be connected to the EB/NF connector, another option was the FSE 2,7 for F1 / FSK radioteletype and Hell reception and for one or double channel radioteletype reception the Telegraphy Adaptor FSE 1300.
From todays point of view, the E-309 is a collector's item as one of the classic German maritime receivers. With it's single conversion circuitry, it is a good performer for the reception of the international shortwave broadcasters as well as some amateur radio or maritime communications traffic. The audio quality is good, the tuning scheme with the electronic 20 kHz interpolation bandspread is outdated. SSB reception with the BFO is substandard from todays point of view.
© Martin Bösch