Rohde & Schwarz EK 070
manufactured by Rohde & Schwarz, Munich.
The EK 070 general coverage receiver from Rohde & Schwarz was introduced in 1979; it has a PLL synthesis circuit, the digital frequency display indicates the reception frequency with an accuracy of 10 Hz. As one of the first shortwave receivers from R&S, the EK 070 has direct frequency input capabilities and thirty digital frequency memories.
- Principle: Double conversion superhet, IF 81.4 MHz, 1400 kHz
- Operation modes: A1 with BFO, USB / LSB, AM (A3)
- Frequency range: 10 kHz - 30 MHz
- Frequency display: digital display 10 Hz, LED or LCD display
- Frequency memory: none
- Signal processing: RF gain, AGC fast/slow
- Sensitivity: CW to 0.1 μV, SSB < 1 μV, AM (A3) < 5 μV / Selectivity: 0.15 kHz, 0.3 kHz, 0.6 kHz, 1 kHz, 1.5 kHz, 3 kHz, 12 kHz and + and - 3.1 kHz SSB (-6 dB).
- Mains operation: 110/120 / 220-240 V
- 483 x 132 x 515 mm, weight 23 kg
The Rohde & Schwarz EK 070 was offered in a tabletop cabinat or as a 19 inch rack mountable unit. As a rack mount unit it measures 48.3 x 13.2 x 51.5 cm and has an astonishing weight 23 kg, which is much for its dimensions.
The receiver can be operated from different mains voltages of 110 / 120 and 220 / 240 V.
The front panel of the commercial receiver has a very straightforward structure:
On the left is the signal strength meter, on the top right the monitor loudspeaker, in between the red LED display, which provides information about all essential operating parameters.
The tuning knob is located below the signal strength meter, the three grey buttons in the left group of push-buttons are used to select the tuning steps. The middle buttons set the operation mode, A1 stands for CW reception with BFO activated, A3 for conventional AM and -/+A3J for single sideband reception. F1+/- activates FSK reception for radio teletype, the EK 070 has a line current output for direct control of a teletype machine, this can be switched on and off with STOP TTY.\. The grey keys to the right activate the fast and slow AGC and in position MGC the manual RF gain control.
The grey numeric keys in the right-hand numeric keypad can be used to directly enter a desired frequency (with leading 0), the CLear key deletes incorrectly entered digits, and when the last digit is entered, the receiver jumps directly to the desired frequency. Similarly, the BFO frequency is entered by pressing the BFO key followed by +/- and two digits. The desired IF filter is activated by pressing BBR/BW followed by one of the digit keys; the +/- keys can also be used to select the next wider or narrower IF filter.
With STO CHAN followed by two numeric keys a frequency can be stored in one of the thirty frequency memories, RCL CHAN followed by the numeric keys recalls the stored frequency.
The EK 070 can be used to search through the stored frequencies in a search run with a selectable response threshold. Several EK 070 receivers can be operated remotely with a operator unit GB 170; the detailed manual provides information on the functions.
On the right below the monitor loudspeaker is the volume control NF - AF, at the bottom right the headphone jack and in between a button to lock the entire keypad. The monitor speaker is switchable, as is the intensity of the illumination of the front panel elements.
The operation scheme is uncomplicated: After connecting mains and antenna, switch on at the top right, select operation mode (A1 (CW), A3E/J3E (SSB) or A3B (AM)), a suitable IF filter is automatically suggested. For the AM Operation mode, the fast AGC should be selected, otherwise the slow AGC. Now the frequency can be tuned in with the tuning knob or directly entered with the frequency keys (with a leading „0“) to an accuracy of 10 Hz; when the last digit is entered, the receiver jumps directly to the desired frequency.
The receiver is highly stable, very sensitive, selective and, as usual with Rohde & Schwarz, the occurrence of mirror frequencies and other „ghost“ signals is not to be expected: you are sitting in front of a professional receiver.
The EK 070 is an excellent general coverage receiver that can be used universally and covers all common operation modes even in its standard configuration.
The stability is excellent, the receiver can be recalibrated with a highly stable frequency standard (signal generator, frequency standard or the carrier of a highly stable broadcast transmitter), but remember that the frequency stability of an external frequency standard must be very high to outperform the synthesiser of the receiver.
Technically, after a switchable attenuator, the signal first passes through a low-pass filter (< 500 kHz), a band-pass filter 500-1500 kHz for mediumwave or a high-pass filter for frequencies above 1.5 MHz. Optionally, an automatic preselection from 8 suboctave filters is provided. First, the antenna signal is converted to 81.4 MHz and passes through a 12 kHz crystal filter. After conversion to the second IF of 1400 kHz the signal passes the filter bank. After the IF amplifier stage, the signal is fed to an envelope demodulator for AM reception, for CW & SSB reception the BFO is switched on, for F1 / FSK reception the signal is amplified, and is feed through a limiter stage to the phase demodulator. The FSK demodulator controls the FSK tuning display and the receiver can directly drive a teletype machine.
The set is solid state.