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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.
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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 2.5-24MHz divided over two ranges:
- 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 frequency range.
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The frequency scale was more or less linear and was adjusted with a
crank that could be folded away; one at either side of the unit.
The image above shows both cranks in their operational position.
Another example of a receiver that used permeability tuning is the
American RBZ Receiver that was used during WWII (1943).
Power for the FE-8 is supplied by the internal 6V/225mAh DEAC cell.
In full operation the receiver consumes no more than 8mA.
The battery can be charged with the supplied mains charger (see below).
Furthermore, an external 6V DC source can be connected to a 2-pin LEMO
socket at the rear of the unit (aside the battery compartment).
Also at the rear is a small coaxial LEMO socket that allows connection
of the side-tone cable from the transmitter.
The receiver is known as FE-8 (Fernmelde-Empfänger,
communication receiver),
BN-58,
Empfänger SP-15 and
SP-20E
(as part of the SP-20 spy set).
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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
(image #5)
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.
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Below is the block diagram of the FE-8 receiver, 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 of
1.180 MHz, which produces a 455kHz signal that is amplified and fed
to a detector. The output of the detector is amplified to a suitable level
for 600-4000Ohm headphones. For the reception of CW (morse), the signal
of a switchable BFO is mixed with the 455kHz signal in the 3rd IF amplifier.
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The filter between the 2nd mixer and the IF amplifier
is a mechanical Collins band-pass filter
which is just 3.1kHz 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.
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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.
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The 3rd image
below clearly shows 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.
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This small charger was supplied to allow the internal 6V DEAC cell
to be charged in a standard mains wall socket. The outer shell can be
removed and will hold the DEAC cell. The shell is then placed back
on the charger and the complete assembly is inserted into a wall socket.
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© Copyright 2009-2011, Paul Reuvers & Marc Simons. Last changed: Tue,12 Apr 2011.22:38:08
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