The receiver of the FS-5000 is a highly compact unit that can
be used stand-alone or
as part of a complete radio station. When used as
part of the full FS-5000, it is located at the
front center of the radio,
in between the batteries and the DSU. The receiver is known as
E-5000 or E-5000M.
It is suitable for the reception of (digital) QPSK signals and for (analogue)
USB signals .
When used as part
of the full FS-5000 radio station, the receiver is fully
controlled by the DSU. The RX-frequency is set on the DSU in the Receive-menu
(Empfang) and the receiver delivers the demodulated signal to the DSU where
the encrypted message is stored.
The image on the right shows a typical E-5000 receiver. At the rear (right
in the picture) is the socket for connection to the transmitter. At the side
of the receiver is a narrow control panel
that is used in stand-alone mode.
At the front is a 45° sloped edge
with a socket for the earphone.
In normal use (i.e. as part of the full FS-5000 station), the receiver
is connected directly to the transmitter, from which it gets its power and
antenna signal. The receiver is extremely sensitive and even the weakest
signals can be picked up easily with a simple antenna. It is suitable for
frequencies between 50KHz and 30MHz, albeit with lower sensitivity
between 50KHz and 1.6MHz.
In case of an emergency, e.g. when one or more of the other modules have
broken down, the receiver can be used stand-alone
for the reception of voice and morse signals.
In that case the H-bar is used and an
is connected directly to the receiver (see below). A telescopic antenna,
which is part of the toolkit, can be mounted onto a screw-on terminal on
The receiver is intended to be used as an integrated part of the FS-5000
radio station. That means that it is installed in its default position at
the front center and that it is fully controlled by the DSU.
It is constructed in such a way that its
can not be used in this situation.
The receiver has a narrow 45° front panel with a socket for the earphone
and a volume control knob. At the left is an adjustment screw that allows
fine-tuning of the frequency ±3Hz. Do not alter this setting!
There are also two green LEDs on the front panel, marked + and -.
The image on the right shows the complete FS-5000 radio station with the
receiver at the front center. The DSU is mounted to its right and mates
with the 25-way socket on the right side of the receiver.
The small control panel
of the receiver is now fully covered by the DSU.
The antenna socket on top of the receiver is not used in this situation,
as the receiver gets its HF input from the transmitter. Although it is not
necessary, the earphone can be connected to the front panel of the receiver
and can be used for monitoring reception.
Note that in this mode,
both switches on the side-panel of the
receiver must be set to the lower position (300/OFF).
Never alter the setting of the Δf adjustment at the front panel!
Please take this warning seriously. The Δf adjustment has been calibrated
at the factory during production of the receiver and is extremely critical,
due to the narrow-band nature of VSB-modulation. Various collectors have
tried altering the setting and found it extremely difficult, if not impossible,
to restore the original calibration.
The receiver has been designed in such a way
that it can also be used stand-alone.
This might be useful in case of an emergency, for example
when one or more of the other modules have been lost or are broken.
The receiver can then be used for the reception of spoken messages or morse.
Please note that German version of the E-5000M has to be
modified for stand-alone use.
For stand-alone operation, the H-bar should be
attached to the rear of the receiver.
It should be connected to the socket that normally mates with the
transmitter. Next, a single battery
is place aside the receiver and is also connected to the H-bar.
The two battery-slots
on the other side of the H-bar are blocked in this situation.
A suitable earphone is supplied with the toolkit.
It can be connected to the
headphones socket on the front panel of the receiver. The telescopic antenna
(also in the toolkit) should be mounted to the antenna terminal on the top
Note that the telescopic antenna must be fully seated
(i.e. all the way in) before it can be used.
The socket contains a switch that is engaged by the threaded part at
the bottom of the antenna.
The receiver is now ready for use and can be controlled from the
small control panel
on its right side. In normal use (as part of the full radio
station) this control panel is covered.
Turn the receiver on with the rightmost switch
The display should now show 00000.
Immediately after switching on, the decimal dot (.) will be
visible on each digit in the display.
Next, use the two push-buttons to the left of the display to set the
desired frequency. First press the button ←f a number of times
until the dot is visible only on the
digit you want to change.
Then use the f↑ button to
set the desired value.
Repeat this until
all digits are set. Then press ←f again until the
to the left of the display goes off. If an earphone is connected to
the receiver's front panel, any signal on the selected frequency should
now be heard.
The volume can be adjusted
with the black knob on the front panel.
In the example photographs we've selected 07020, which is a frequency
of 7.020 MHz in the 40m amateur radio band on which you are likely to hear
morse code signals from time to time.
Note that for voice reception, the bandwidth switch
should be set to 3000 Hz.
The transmitter uses a sophisticated technique called Vestigial
Side Band modulation (VSB) for the transmission of data at very high speed
(2000 baud) through a narrow-band HF radio channel. Although generating
a VSB-signal is relatively simple, it requires an extremely complex
(and large) decoder at the receiving end. As a result, the receiver in the
FS-5000 field station uses Single Side Band modulation (SSB, J2B)
to receive single-channel Frequency Shift Keying (FSK) data at 75 baud.
The demodulated signal is sent to the DSU which converts it
into digital data again.
The image above shows how data is exchanged between the
base station and
the FS-5000 field station.
Sending data at the highes possible speed is
of the utmost importance in order to minimise the chances of Direction
Finding (DF) by the enemy. Receiving data does not require high speed,
as the base station is generally located in a remote position, often
hundreds or even thousands of kilometers away from the field.
It can take its time, and its location is not secret.
Although the receiver is one of the smallest parts of the FS-5000 it is the
core frequency generating component. It not only produces the various
frequencies needed for the receiver itself, but also the frequencies for
the transmitter. In fact, the transmitter can not function without the
receiver. The block diagram below shows how the main FS-5000 components
The synthesizer inside the receiver produces all HF signals for the receiver
and the transmitter, from a 10MHz TCXO that can be adjusted ±3Hz at the front panel. It has been calibrated at the factory and should not be changed.
The frequency is controlled by the DSU. From the received USB signal,
the demodulator discriminates the 75 baud FSK signal and feeds it to the DSU.
The image above shows a more detailed block diagram of the receiver.
Please note that this diagram is an educated guess, as we don't
have any technical documentation at present.
The antenna input is at the top left and the audio output is at the bottom
The 1st IF is at 50.2MHz, which is the result of the input signal that is
mixed with the local oscillator, ranging from 52 to 80 MHz, using high-side
injection. The 2nd IF is at 200kHz which is commonly used in Telefunken designs.
After a selectable mechanical filter (300Hz or 3000Hz), a 3rd mixer is used
to convert the 200kHz into an audible LF-signal and finally a digital
Although it looks rather simple from the outsite, the device is in
fact a sophisticated high-end superheterodyne receiver, built to the highest EMC standards. The compact case consist of 5 large PCBs plus a
smaller daughter card on one of them. It can be opened from both sides.
The image on the right shows the first stages of the receiver, which become
visible when the top panel (held in place by 6 bolts) is removed.
At the right is the front-end with the socket
for the (optional) telescopic antenna.
Only when the antenna is fully screwed-in, a switch
mounted to the side of the socket is engaged and the new input
is selected. Without the telescopic antenna, the input signal is taken
from the transmitter.
At the left is the 1st IF stage at 50.2 MHz,
which has a 4-stage crystal filter at its center.
The rest of the receiver can only be accessed from the bottom.
After removing the bottom panel, the solder side
of the bottom-board becomes visible. The entire bottom section can be
removed by releasing 4 recessed bolts. This gives access to the
2nd IF-stages that are mounted below the front-end.
The 2nd IF frequency is 200 KHz for which two
mechanical 200 KHz filter are present on the lower board.
The upper board contains a Telefunken OEM chip
marked TEZ - C 18081 S - 103707. The function of this chip is
currently unknown. The boards are connected to the synthesizer
which resides in the bottom section.
The bottom board
holds the synthesizer, the (simple) control logic
and the interface logic. The synthesizer is shielded-off
from the rest and connects to the 2nd IF
via 4 coax cables.
The image on the right shows the bottom board from which the small
daughter card has been removed and lifted. The daughter card contains
a canned circuit marked KS 1075
that is located on top of a similar
circuit on the bottom board itself, marked
The board also contains a 10MHz TCXO that is mounted just behind the
transmitter-connector at the right.
The two cans (KS-1075 and KS-1076) probably contain purpose-built
thick-film circuits for the interfaces, the user I/O and sythesizer control.
In the image above, the synthesizer is just visible at the top.
At the bottom right is the 5-digit LED display that is controlled
by the KS-1076.
The RX frequency is controlled by the DSU and can be adjusted between
50 KHz and 30 MHz in steps of 1 KHz. An adjustment screw at the front
panel, marked ΔF, was used to calibrate each receiver at the factory.
Never change the setting of this adjustment!
It allows a frequency adjustment of ±3Hz and is extremely critical.
The two LEDs on the front panel, marked + and -, are indicators
for RTTY signals and respond to 1140 and 1240 Hz respectively.
Never alter the setting of the Δf adjustment at the front panel!
Modifying E-5000M for stand-alone use
The German version of the E-5000M receiver has been modified in such a way
that it can not be used in stand-alone mode as described on this page.
This was probably done to avoid problems when using the FS-5000 in the field.
The modification locks the receiver in the OFF position and in narrow-band
mode (300Hz). Luckily the modification can easily be undone within minutes.
Next, locate the corner with the two (red)
single-pole double-throw switches, and cut the two wire links indicated
in the image above. Be careful not to cut any of the other wires and
ensure that the cut-out pieces do not disappear into the body of the
receiver. The modification is now undone. Close the bottom panel and
replace the 6 cross-head bolts. Then test the receiver in
stand-alone mode by connecting it to a single battery
using the H-Bar
and turning the unit ON.
When using the receiver stand-alone, it might be necessary to supply a 14.4V
from an external PSU directly to the receiver. This can be done in two ways.
If the H-bar is present, it should be connected to the rear of the receiver,
as described above under Stand-alone use. If a charged battery is
available, connect it to the H-bar and use the receiver as described above.
If the H-bar is available, but you don't have an original battery, the
external power source can be applied directly to the two thick terminals
of the battery socket of the H-bar. The image on the right shows a simple
red/black cable with two special jacks
that can be fitted to the power terminals.
Detailed images can be found below. Please note that the contact
closest to the receiver should be connected to
the +14V rail.
Please note that the receiver should be powered by at least 14V (ideally
it should be 14.4V), as otherwise the receivers's PLL will not lock.
If the H-bar is not present, the 14V from the external power source can
be applied directly to the complex socket at the rear of the receiver.
This socket is normally used to connect the receiver to the transmitter
and carries a large number of complex signals and voltages.
Here is the layout:
Connector at the rear of the receiver
It should be possible to modify an existing 37-way D-type female connector
to fit the above socket. Remove the unwanted pins and drill out the areas
for the 4 large coax connectors. Alternatively, you may create an
improvised power cable
by using a two-pin female connector
soldered to two wires. Note that the 0V wire (black)
should go to pin 17 of the connector.
- Frequency range: 2-30MHz
- Extended range: 50kHz-1.6MHz (reduced sensitivity), 1.6-2MHz
- Step size: 1kHz
- Accuracy: ±1Hz
- Modulation: USB (J2B)
- Data speed: 75 baud
- Synchronisation time: < 300ms at S/N > 20dB
- Helmuth (Jimboy) Meyer (DJ2EI), Agentenfunk!
Backgrounds on many different spy radio sets.
Retrieved June 2008.
Website closed as of 30 April 2010.
- United States patent 4,780,884, Suppressed Double-Sideband Communication System
Filed 13 April 1987. Approved 25 October 1988.
Previously filed as 741,026 (3 June 1985) and 835,265 (3 March 1986), both
abandonned. Retrieved April 2012.
- United States Patent 4,730,345, Vestigial Sideband Signal Decoder
Filed 4 April 1986. Approved 8 March 1988. Retrieved April 2012.
- United States Patent 5,663,773, Demodulator for a Complex-Value VSB Signal
Filed 20 November 1995 on behalf of ANT Nachrichtentechnik GmbH, Backnang (Germany). Approved 2 September 1997. Retrieved April 2012.
- Prof. Dr.-Ing. Dietmar Rudolph, Einseitenband & Restseitenband Modulation
TFH Berlin - Telekom TT - IBH. (German) Date unknown. Retrieved April 2012.
- Feldstation FS-5000M, Technisches Handbuch, Teil 1, Beschreibung
Field Station FS-5000, Technical Manual, Part 1, Description (German).
- Feldstation FS-5000M, Technisches Handbuch, Teil 2, Bedienungsanleiting
Field Station FS-5000, Technical Manual, Part 2, User Manual (German).
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