E-657, Telefunken E 1501; developed and produced by AEG - Telefunken AG, Ulm.
Top range shortwave communications receivers have been used to monitor shortwave External services of foreign countries, one of the receivers in use was the Telefunken E-1501, which carried the military designation E-657.
The PLL synthesized communications receiver has an excellent frequency stability and a high accuracy of the frequency display as well as a good selection of I.F. filters ordered to individual requirements of the user.
The Telefunken E 1500 / 1501 is a commercial communications receiver, it is intended for 19„ rack mount, it's dimensions are 54,4 x 14 x 40 cm and it's weight arount 17 kg.
The complete receiver has a modular construction behind the front panel. The receiver E 1500 is the main component, optional components are the DE 1500 (this second demodulator is used for independant side band / ISB reception modes A3B/A7B), the radio teletype decoder TD 1500 (F1/F4/F6A) and the AD 1500 dual antenny diversity option, which make a complete E1501.
The standard mains power supply module is the NS 1500 to power the radio from 110 / 220 V, for mobile use, a battery power option BS 1500 running from 24 V DC has been available.
The frontpanel design is very straightforward: in the top row all indicators, in the bottom row of controls at the left the main tuning knob, followed by all other controls and at the right below the internal monitor speaker the mains switch.
The analog signal strength meter can be set to display the A.F. level, in radioteletype modes, it can display the current and audio level of the signal driving the teletypewriter.
The big red LED display will indicate the reception frequency with a resolution of 10 Hz, two LEDs on both sides indicate the selected antenna when antenna diversity is active (the more powerful signal of two distant shortwave receiving antennas will be fed to the demodulator).
A row of LED's are used for signal analysis: when an AM signal is correctly tuned, the middle red LED indicates carrier center, rows of green LEDs both sidebands. In single sideband mode, only the respective LEDs are active, in radioteletype transmissions F1, the LEDs are used to display the Mark and Space signals.
At the right, next to the LED display, you find an internal monitoring speaker, just below the mains switch and the headphones jacks.
The main tuning knob at the left hand is equipped with an electronic flywheel effect, one turn will tune the set 1,8 kHz, the tuning speed will increase to 18 kHz / revolution when the tuning knob is rotated quickly. Two UP/DOWN tuning knobs with a speed of 300 kHz and 3 MHz per second will give you access to the complete shortwave range within a few seconds. To directly access a desired broadcast or amateur band, you need some experience. The switches further at the right activate / lock the tuning mechanism and select one of the two antennas or set to automatic antenna diversity operation.
The following switches are used to select the sidebands in ISB mode A3B, to select automatic or manual gain control, to switch between normal and inverted mode and wide and narrow shift in radioteletype mode and to activate the noise limiter and the internal monitor speaker.
In the row of rotary controls, the leftmost is used as A.F. gain / volume control, next is the BFO, the manual R.F. gain control and the I.F. filter switch and modes switch at the right.
The receiver offers a great selection of high quality intermediate frequency filters: the 50, 150 and 750 Hertz filters are used for CW reception, 750 Hz for radioteletype operation, 3 and 7 kHz for AM reception. +3 is the filter for the upper sideband (in the manual, You will find OSB for Oberes Seitenband) and -3 for the lower sideband (USB stands for Unteres Seitenband, remember, this is a german set…).
To use the modes switch, you need some minimal knowledge about the international designations of transmission modes: A1 stands for CW / morse code reception, A2/A3 for normal AM reception (the wider dark bar indicates the AM position with a slower AGC decay time), A3J is for reception of single sideband transmissions and signals with reduced carrier, A3B is for independent side band telephony, A7B stands for ISB telegraphy with two independent teletype / telegraphy channels, F1 and F4 are for radioteletype reception.
Apart from the cryptic frontpanel lettering with it's many different symbols, as typically found on commercial shortwave receivers, the operation scheme of the E 1500 is straightforward and simple. Switch on the receiver with the mains switch below the monitor speaker grill and make sure, the speaker is active.
To tune in a signal in the 49 m broadcast shortwave band, set the modes switch to A2/A3, the bandwidth to „7“ and use the fast UP/DOWN tuning buttons to tune to a frequency near and the tuning knob to the exact frequency - when the receiver is tuned to 6155.00, you should hear the signal coming from Vienna. The red LED active in the signal analysis panel informs you, that the technicians in vienna have tuned their transmitter exactly on the correct frequency.
To tune in an amateur radio station or a volmet weather report in single sideband mode, use A3J as reception mode, select the -3 filter and slowly tune up and down until the speakers voice does not sound like Mickey Mouse anymore.
The Telefunken E 1500 / E-657 is a premium grade communications receiver offering you stable reception of AM and single sideband signals with a wide choice of I.F. filters; in comparison to amateur radio receivers, the set is lacking some possibilities of „postprocessing“ a disturbed shortwave signal; you have to do without passband tuning and notch filter - these features are usually not present in commercial shortwave receivers and the Telefunken E 1500 makes no exception.
The set is completely solid state.
For the Telefunken receiver; an external frequency input keyboard was produced by the Swiss company Elektron in Au ZH. I have no information, if the ET1500 was also used in the army or only in commercial radio services.