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FE-8   BN-58
Portable solid-state short wave receiver

This receiver was developed by the German manufacturer Wandel & Golterman (W&G) in 1958 and was given the designator BN-58. It was used with the SP-15 spy set and later also with the SP-20 spy set. W&G is widely known for the production of high-end electronic test equipment such as audio and HF spectrum analyzers. The BN-58 is also known as the FE-8 or as Empfänger SP-15 when part of the SP-15 radio station, but also as SP-20E when it was part of the SP-20 radio set.

The BN-58 is one of the first small receivers that was completely transistor-based and featured very low power consumption. The double conversion superheterodyne receiver has an IF of 1.635 MHz and covers 2.5-24 MHz divided over two ranges, selectable with the second knob:
  • 2.5 - 9.1 MHz (green)
  • 9.1 - 24 MHz (red)
The receiver features permeability tuning (coil tuning), similar to Collins receivers, and had a separate tuner for each of the above ranges.
  

Because the permeability tuning is mechanically calibrated, the frequency scales are nearly linear. Each tuner has its own tuning coil that can be adjusted by means of a fold-out crank; one at either side of the unit. The image above shows both cranks in their operational position. Another example of a receiver that uses permeability tuning is the WWII American RBZ Receiver.

Power for the FE-8 is supplied by the internal 6V/225 mAh battery, that can be charged with the supplied mains charger. Furthermore, an external 6V DC source can be connected to a 2-pin LEMO socket at the rear of the unit. In full operation the receiver consumes no more than 8mA. Also at the rear is a small coaxial LEMO socket that allows connection of the side-tone cable from the transmitter. Audio is delivered into 2000 Ω headphones that can be connected to the 2-pin socket at the far right of the front panel. Volume is adjusted with the rightmost knob.

Receiver with both cranks stowed away Receiver with both cranks in the operational position The green frequency range (2.5-9.1MHz) The red frequency range (9.1-24MHz) The controls on the font panel FE-8 with home-made 6V NiCd battery 2000 Ohm earphone connected to the FE-8 FE-8 connected to external power source
A
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A
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Receiver with both cranks stowed away
A
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Receiver with both cranks in the operational position
A
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The green frequency range (2.5-9.1MHz)
A
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The red frequency range (9.1-24MHz)
A
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The controls on the font panel
A
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FE-8 with home-made 6V NiCd battery
A
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2000 Ohm earphone connected to the FE-8
A
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FE-8 connected to external power source

The images above give a clear view of the various control of the FE-8 receiver. Please note the two notches on top of the unit that could be used to 'feel' the currently selected band. In the image, the green band is selected (2.5-9.1MHz) and hence the rightmost notch protrudes the top of the case to indicate the use of the green scale. When both notches are 'in', the receiver is 'off'.

Block diagram
Below is the block diagram of the FE-8 receiver, which is based on the work of Helmuth Meyer (DJ2EI) [1]. At the left are the two different tuners (one for each frequency range). The first local oscillator and mixer are inside the tuner and produce an IF1 at 1.635MHz. This signal is mixed with the 2nd IF oscillator at 1.180 MHz. It produces a 455kHz signal that is amplified and fed to a detector. The output of the detector is amplified to a suitable level for 600-4000 Ω headphones. For the reception of CW (morse), the signal of a switchable BFO is mixed with the 455kHz signal in the 3rd IF amplifier. In the leftmost position the BFO is turned off.



The filter between the 2nd mixer and the IF amplifier is a mechanical Collins band-pass filter which is just 3.1 kHz wide. In the above block diagram, the two tuners are each simplified to a single block. A more detailed block diagram of a single tuner is given below.


Each tuner is in fact a very complex device with multiple permeabilty tuning coils, resulting in a nearly linear scale. Turning the tuning crank, moves the ferrites in and out of the coils. In order to get rid of any linearity-errors, a sophisticated mechanical correction adjustment is present. Please check the images below to see this wonderful piece of engineering. An adjustable 'glide path' that is sensed by a 'finger' which in turn moves a second ferrite. The glide path represents in fact the correction curve for the frequency scale. Never alter the adjustments of this path.

B
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B
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B
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B
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B
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Battery
The FE-8 can be powered by an internal 6V battery, that consists of five stacked 1.5V NiCd cells. As the original battery is no longer in production, it may be difficult to find a replacement. It should be relatively easy however to create a good alternative from existing 1.2V NiMH cells. Suitable replacement batteries are now readily available from Akkuumbau in Germany [5].

The FE-8 can also be powered from external 6V DC source that should be connected to the power socket at the rear of the device, close to the battery compartment. This sockets needs a 2-pin LEMO connector of which both pins are used for the plus connection, whilst the shield is used for the ground (negative) contact.

The image on the right shows the charger that was supplied with the FE-8. It allows the 6V battery to be charged directly from the 220V AC mains. The battery is placed inside the outer shell, which is then fitted onto the charger.
  

The complete assembly can then be inserted into a standard wall socket. Once the battery is full, it can be placed inside the battery compartment of the FE-8 again. Alternatively, the battery can be charged directly inside the FE-8 by supplying a slightly higher voltage (7.2V) to the external DC socket at the rear. The same type of 6V stacked battery is used in the calibrator (see below).

FE-8 with home-made 6V NiCd battery Battery fitted inside the battery compartment Removing the battery External power lead External power connected to the FE-8
C
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C
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1 / 8
C
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C
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C
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FE-8 with home-made 6V NiCd battery
C
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Battery fitted inside the battery compartment
C
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Removing the battery
C
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External power lead
C
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External power connected to the FE-8

Calibrator
The BN-58 was a very sensitive receiver with a nearly linear scale, making it easy to tune it to the desired frequency. Nevertheless, it had to be calibrated from time to time. This was done by means of the external calibrator shown in the image below, which is in fact a frequency marker.

It consists of a 15 cm long metal cylinder with a 2-pin connector at the end. The connector was inserted into the antenna and ground sockets at the left front of the receiver. The calibrator is activated by pressing (and holding) the small brown push-button on top of the connector.

The calibrator is powered by an internal 6V battery that consists of five stacked 1.2 NiCd cells; the same one as is used for the FE-8 receiver itself. Batteries of this type may be hard to find, but it should be possible to create one from standard 1.2V NiCd or NiMH cells.
  
FE-8 calibration device

Inside the device is a so-called comb generator [4]; a device that generates multiple harmonics from a single base frequency, all of which are identical in strength. When used with a rounded base frequency (e.g. a 1 MHz crystal) it produces a reference signal (marker) at regular (1 MHz) intervals. The device is constructed in such a way that its signal is rather weak (typically -60dBm or lower), so that the sensitivy of the receiver can be checked at the same time.

The device has two internal reference crystals plus an external one that can be inserted in the crystal socket on top of the device. At the front is a three-position rotary switch with three settings, marked I, II and III. It is used to select the mode of operation:

  1. 100 kHz
    This setting produces a -80dBm marker signal at 100 kHz intervals.

  2. 1 MHz
    This settings produces a -60dBm marker signal at 1 MHz intervals.

  3. Crystal
    In this mode, the external crystal socket on top of the device is used. It can be used with any arbitrary frequency that is within the range of the receiver. We've tried, for example, a standard amateur frequency crystal of 3.575 MHz, which generates a marker at 3.575 MHz, 7.150 MHz, etc. In this mode, the signal strength depends on the crystal's activity.
FE-8 calibration device FE-8 calibration device Antenna connector and power switch Battery compartment MODE selector (I, II or III) Looking into the battery compartment Install the battery this way (+ on the left) External crystal socket
Crystal fitted into the socket Calibrator and FE-8 receiver Calibrator connected to the FE-8 Activating the calibrator Using the calibrator with a standard 3.575 MHz amateur frequency crystal Verifying the 100 kHz markers on a spectrum analyser Verifying the 1 MHz markers on a spectrum analyzer Verifying the amateur frequency on a spectrum analyzer
D
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D
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FE-8 calibration device
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FE-8 calibration device
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Antenna connector and power switch
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Battery compartment
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MODE selector (I, II or III)
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Looking into the battery compartment
D
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Install the battery this way (+ on the left)
D
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External crystal socket
D
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Crystal fitted into the socket
D
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Calibrator and FE-8 receiver
D
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Calibrator connected to the FE-8
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Activating the calibrator
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Using the calibrator with a standard 3.575 MHz amateur frequency crystal
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Verifying the 100 kHz markers on a spectrum analyser
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Verifying the 1 MHz markers on a spectrum analyzer
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Verifying the amateur frequency on a spectrum analyzer

Designators
  • FE-8
  • BN-58
  • SP-20E
  • Empfänger SP-15
References
  1. Helmut 'Jim' Meyer, HS0ZHK, My way to Ham - Radio and beyond
    Detailed technical description of the FE-8 (BN-58) in German and English.
    Website QRZ.COM. Personal correspondence. Retrieved April 2013.

  2. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004

  3. Wandel & Goltermann, BN-58 circuit diagram
    30 September 1960.

  4. Wikipedia, Comb generator
    Retrieved April 2013.

  5. Akkuumbau, FE-8 replacement battery
    Retrieved 21 August 2017.
Further information
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Crypto Museum. Created: Monday 03 August 2009. Last changed: Monday, 21 August 2017 - 15:20 CET.
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