Telefunken E 724 SW/2
Telefunken E 724 SW/2, component of the Shortwave Receivng System Transradio; manufactured by Telefunken AG, Ulm.
The E 724 SW/2 was developed in the seventies, it is a modular transistorised search and surveillance receiver, which was mainly used by the German army and navy.
The receiver was the core piece of the Long Range Shortwave Receiving System Transradio 11. The Telefunken system with the E 724 receiver without 100 Hz locking function was sold in various configurations as Transradio 11 - 16.
- Principle: single conversion superhet, IF 525 kHz
- Operation modes: A1 with BFO, USB / LSB, AM (A3)
- Frequency range: 1.5 - 30.1 MHz
- Frequency display: digital display, 100 Hz; Nixie tubes
- frequency memory: none
- Signal processing: RF gain control, AGC
- Sensitivity: CW (A1) < 0.2 μV / Selectivity: 0.2 / 0.5 / 1.5 / 3 / 6 / 12 kHz (-3 dB)
- Mains operation: 110, 220 V
- Batteries: 21.5 - 30 V
- in desktop cabinet: 274 x 315 x 350 mm, weight 24 kg
- TG 455 FSK / radio teletype demodulator
- SG 455 Visual display for mark and space signals
- AD 455 antenna diversity module
The set looks very similar to the shortwave receiver E863, but it has a signifikant difference in that it does not have a 100 Hz locking function (which is activated by the green button on the left above the tuning knob found only in the E863). In combination with an FSK demodulator, panoramic display and other accessories, the set is part of the Telefunken long distance receiving systems Transradio 11 to 16.
As a rack-mount unit, the set measures 256 x 270 x 324 mm and takes up the width of only half a 19-inch rack; as a table-top unit, it measures 274 x 315 x 350 mm and and has a weight of 20 and 24 kg, respectively.
The receiver can be supplied with 110 or 220 V mains and consumes up to 100 W when heating up, it can also be operated with 21.5 - 30 V direct current from a vehicle battery.
The headphone jack is the only connector on the front panel, the other connectors are located at the back of the receiver. Depending on the receiver version, the operating elements are labelled in German or with international symbols.
On the somewhat unusually designed front panel, the main switch is located in the upper left corner with the positions Off / Preheat / Operation / Receiver on, Loudspeaker off. To the right of it, a six-digit Nixie tube display indicates the reception frequency with an accuracy of 100 Hz.
In the lower left part of the front panel, you find six controls one above the other: the switch at the top left lets you select the IF filter bandwidth, the receiver has filters of +/- 100 Hz, +/- 250 and 750 Hz for CW reception, +/- 1.5 kHz, +/- 3 and 6 kHz for AM reception as well as a 3 kHz USB and LSB filter each. Right next to it is the range switch, it selects the band ranges 1.5 - 3.48 / 3.47-7.49 / 7.45-15.5 or 15.4-30 MHz. Below this is the BFO control used for CW reception and the operation mode switch. The first three positions activate the automatic HF control (AGC) in the operation modes F1/F6 (FSK), A2/A3 (AM) with long and short time constant. The middle three positions deactivate AGC, RF gain is under manual control, for A2/A3 (AM), A3J (SSB) and A1 (CW), the last two positions select AGC for A1 (CW) and A3J (SSB) reception. Other receivers have a more simple solution for this…
The two bottom controls for RF and AF gain are self-explanatory, as are the headphone jacks and the switch for the noise limiter.
In the lower right quadrant of the front panel is the measuring instrument, which displays the signal field strength, the line AF level or the temperatures of thermostats 1 and 2 (should be in the green range) at the touch of a button, and the monitor speaker is located just below it. The main tuning knob is easy to find, in contrast to the E863 the 100 Hz - detent function is missing, the receiver is fully tunable.
For standard operation, the receiver is switched on at the top left, the voltage indicator should read between the red and white area for mains operation and in the white area for battery operation. After twenty - 60 minutes, the thermostats have reached the operation temperature and the frequency stability is within specifications.
To adjust the frequency, select the appropriate band range and tune with the main tuning knob, there is a fine tuning option in the range +/- 300 Hz to be adjusted for optimum intelligibility when receiving SSB or FSK signals.
For AM reception (A3) the Operation mode A2/A3 with the small or large dot is selected (short or long AGC characteristic), depending on the interference situation the IF filter ±6, ±3 or ±1.5 kHz can be used. For SSB reception (A3J) the 3 kHz filter for the upper or lower sideband is selected, for CW reception (A1) one of the narrowband filters. If necessary, in the middle positions of the mode switch, select a position with manual control of the RF gain, adjust the volume with the AF control. To liste to the station, madke sure the main switch is in the ON position and not in the ON/speaker off position.
Optionally, the E 724 Kw/2 can be used together with a TG 455 FSK radio teletype demodulator, a panoramic display SG 455 (this configuration was sold as „Long distance receiving system TRANSRADIO 11“. If quipped with other optional modules, the E 724 also allows the reception of complex multi-channel - single sideband transmissions…
The Telefunken E 863 Kw/2 and the E 724 Kw/2, which is very similar except for the 100 Hz locking function, are quite compact fully transistorised operating receivers. They give you reliable reception of shortwave external services of international broadcasters, amateurs and special radio services.
Single conversion superhet.
The set is solid state.