E-658, all wave receiver Rohde & Schwarz EK 070; developed and produced by Rohde & Schwarz, Munich.
The PLL synthesized VLF - HF all wave receiver Rohde & Schwarz EK070 has been introduced in 1979. It's digital frequency readout has an accuracy of 10 Hz. The R&S EK070 has been one of the earliest shortwave receivers with direct keypad frequency entry, thirty electronic memories and the possibility of beeing remote controlled by a computer or a secondary controller BG 170.
The E-658 / Rohde & Schwarz EK 070 is a communications receiver which was sold in a desktop cabinet or as a 19 inch rack, the dimensions of the rack version are 48,3 x 13,2 x 51,5 cm and it's weight 23 kg. The receiver comes with an integrated power supply and operates from 110 / 120 or 220 / 240 Volts.
The frontpanel of the commercial receiver is clearly structured:
At the left, you find the signal strength meter, in the right upper corner the integrated monitor speaker an in between the red LED display which will keep you informed on the receiver status.
The main tuning knob is located below the signal strength meter, the three grey coloured pushbuttons lefthand in the left group of pushbuttons select the tuning speed. The middle pushbuttons select the reception mode, A1 stands for CW reception with the BFO activated, A3 for AM reception, +/-A3J stands for single sideband reception, -/+F1 FSK reception for radioteletype, the EK 070 provides a line out jack to control a teletypewriter directly, which can be activated by the STOP TTY button.
The grey pushbuttons at the right activate the fast and slow AGC and the manual gain control MGC operated with the RF Gain control.
The grey numbered pushbuttons in the right group let you select the reception frequency directly. Remember to type in leading zeros, the CLear button lets you delete wrongly entered digits, the receiver is tuned to the desired frequence after the last digit of the reception frequency has been typed in.
Select the BFO offset with the BFO button followed by two digits, the BBR/BW button followed by one of the numbered buttons lets you select the bandwidth filter, you can also select the wider or more narrow bandwith filter by using the +/- keys instead.
STO CHAN followed by two digits will save the active frequency in one of the thirty frequency memory slots, it can be recalled by pressing RCL CHAN followed by the memory channel number. The EK 070 can also automatically scan the saved frequency memories, the receiver can be remote controlled from an external BG 170 controller, the handbook will explain how to proceed with this.
At the right, below the monitor speaker, you will find the volume control NF - AF and a keyboard lock button, below the mains switch the switch to activate the monitor speaker and regulate dial illumination.
Operating the receiver is very straightforward: conect to mains and a decent antenna, turn the set on with the power switch in the right upper corner and make sure, the monitor speaker is on. Select the reception mode (A1 (CW), A3E/J3E (SSB) or A3B (AM)) and the receiver will automatically switch a rexcommended I.F. bandwidth filter; select the fast AGC for Am reception, slow AGC in the other modes and tune to the desired frequency with the main tuning knob or type in the reception frequency with the numbered keys (with leading zeros for frequencies below 10 MHz), it will automatically jump to the desired frequency once you have completed entering all digits down to the 10 Hz digit.
The EK 070 is extremely stable and has an excellent sensitivity and selectivity with it's wide range of bandwidth filters. As with other Rohde & Schwarz shortwave receivers, you won't be confronted with mirrors and spurious signals: the receiver has an ultimate professional design.
After a switchable attenuator, the signal has to pass a low pass filter (< 500 kHz) for VLF, a band pass 500-1500 kHz for mediumwaves and a high pass filter for frequencies above 1,5 MHz. There has been an automatic eight channel suboctave frequency preselection available as an option.
The signal from the antenna is mixed to generate a high first intermediate frequency of 81,4 MHz and will pass through a 12 kHz crystal filter. After the second mixer, where the second I.F. of 1400 kHz is generated, the signal has to pass the I.F. filter bank and will be lead to the AM detector after the I.F. amplifier stages with automatic gain control. A BFO is activated for CW reception, for F1 / FSK reception, the signal is amplified, has to pass a limiter stage and reaches the phase demodulator. FSK demodulator will control the FSK LED tuning control and can control a teletypewriter directly.
The set is completely solid state.
The Swiss Army used the Rohde & Schwarz EK 070 with the designation E-658 with the signals intelligence, 85 receivers and 16 BG 170 controllers have been acquired. This receiving equipment has been replaced by the E-663 / Telefunken E-1800 in 2007.