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E 127 Kw/4 - the Telefunken - "Rainbow Receiver"

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überarbeitet am 16.11.2010

Single conversion, I.F. 525 kHz

Analog dial,

AM, CW, SSB

1,5 - 30,1 MHz

Selectivity -3 dB
0.2 / 1 / 3 / 6 / 12 kHz

Sensitivity
CW < 0,2 uV

RF gain, AGC
Bedienungsanleitung Schemata

The E 127 Kw/4 has been produced in the mid-fifties until the mid-sixties in different variants and has mainly been used by official agencies, for weather reports, press communication and as monitoring and surveillance receiver.
One variant is the military E 127 Kw/5, this receiver is equipped with a front panel protection grid and has all connectors on the front panel, it has been used by the Germany Army (painted green) and Navy (painted blue - grey).
The Swiss Army used it in the commercial variant E 127 Kw/4 painted in grey with connectors on the rear face.
Do not confound the E 127 Kw/4 with the Siemens "Rainbow Receiver" E-310, which has been used quite often for maritime communications.

The receiver measures 550 x 375 x 390 mm and has a weight of 44 kg, it is quite compact compared with the E-104 or the Rohde & Schwarz EK-07; anyway, the set is quite heavy when You try to lift it on the desk in Your shack, it's a irreproachable boatanchor. The receiver can be powered from 110 - 240 V mains and has a power consumption of 70 W with it's eight tubes.

In the middle of the frontpanel, You find the multi - colour semicircular frequency dial, the band segments are colour coded: the 1,5-3,3 MHz range 1 in white, range 2 from 3,2-7,1 MHz in yellow, range 3 from 6,9-14,1 in grey, range 4 from 13,9-22,1 MHz in green and the last range from 21,9-30,1 MHz in red.
At the left of the "Rainbow dial", You find the switchable monitor speaker and at the right the measuring instrument that can be set to display signal strength or the AF level as well as the BFO for CW / A1 reception.

The other controls are located in one row below the frequency dial: from the left the bandwidth selector, the main tuning knob, the band selector with the identical coloured marks, the RF gain control and the AF gain / volume control.
Below at the bottom of the receiver's front panel, You find some headphones jacks on both sides, and the switches for the noise limiter, the automatic gain control (automatic stands for AGC) and the modes switch, which activates the BFO for CW / A1 morse code reception.

As options, the receiver E 127 can be connected to the radioteletype adaptor TgFs 127 (reception modes F1, F3), the single sideband demodulator BP 102 for SSB reception with full (A3a) or reduced carrier (A3b) and the diversity adaptor Abl 305.

The antenna signal is fed via two R.F. amplifier stages (EF85) to the first mixer(ECH81), where the intermediate frequency of 525 kHz is generated. The i.f. signal has to pass two crystal filter stages (EF85) with selectable i.f. bandwidth and will be demodulated (ECH81). For CW reception, the signal of the BFO is added. The audio signal is amplified in the audio final stage (EL84).
Blockschaltbild E 127 kW/4

The Telefunken E-127 Kw/4 with it's "Rainbow dial" is a classic collector's set, it should not be confounded with the Siemens "Rainbow" E-310.
The E-127 is a good performer on the shortwave bands and can be used to monitor some amateur radio traffic in CW and single sideband, it's operation scheme and frontpanel layout is quite straightforward. But the dial accuracy does not meet today's expectations anymore, You cannot be absolutely sure, on what frequency You are receiving a signal - for DXing, a receiver with digital frequency display does a far better job.

© Martin Bösch 26.10.2008 / transl. 16.11.2010