Manpack short-wave transceiver
- this page is a stub
The RUP-12 radio was a family of low-band VHF transceivers
(30-70 MHz), developed in the former Yugoslavia
in the late 1960s 
and built by the Rudi Čajavec factory in Banja Luka
(Bosnia and Herzegovina).
It was intended for communication between infantry companies
and battalions of the Yugoslav National Army (JNA).
The RUP-12 is also known as UGAR-1.
In the late 1970s, the RUP-12 was succeeded by the
which had identical controls but a modernised interior.
The RUP-12 is not suitable for a real voice encryption unit like the
that was used with the later RU-2/2K.
In order to provide at least some level of voice protection on the RUP-12,
a voice scrambler was sometime used, such as the Yugoslav KzU-61
or the American KY-189
that is shown in the image on the right. For the latter, the RUP-12 had to
be modified (+12V on pin 5 of the connector).
➤ More information
The RUP-12 is suitable for all low-band VHF frequencies between
30 and 70 MHz, with a channel spacing of 50 kHz, resulting in
800 discrete channels. The desired frequency is selected by means of
3 rotary switches at the front panel, between 000 and 799.
For conversion between the channel number and the actual frequency,
the following formulas can be used:
As an example, a scale setting of 367, results in
(367+600)/20 = 48.35 MHz. The lowest setting (000),
results in 30 MHz, whilst the highest setting (799) gives
Use formula (2) to calculate backwards.
A frequency of 52 MHz,
results in a scale setting of 20 · (52-30) = 440.
The image below shows a simplified block diagram of the RUP-12,
and is based on several more detailed block diagrams from the
operator's manual . The transceiver parts (TX) are at the top,
whilst the lower parts shows the various stages of the receiver.
The audio frequency stages (AF) are at the bottom right. The receiver is
a straightforward heterodyne with a 1st IF frequency of 10.7 MHz.
Some parts of the receiver's 10.7 MHz section are shared with
the transmitter (AFC).
The transmitter section is shown at the top (in red). The modulator
at the right mixes the audio signal from the microphone with a
10.7 MHz signal from a crystal oscillator. The advantage of using
10.7 MHz is that the crystal reference of the receiver can be used
for selecting the desired transmission frequency.
The most complex part of the transceiver is the crystal reference itself:
The block diagram above shows how the crystal reference is synthesized.
The analogue parts are shown in blue, whilst the (digital) logic parts
are red. The three parts that determine the actual frequency are
shown in blue. The leftmost one is based on a 5 MHz crystal oscillator
with a configurable multiplier behind it. It allows the 5 MHz signal
to be multiplied by 1, 2, 3 or 4. This signal is fed to the first
mixer, where it produces a sum and a difference signal. If we also
take 0 MHz into account (i.e. multiply by 0, i.e. no signal),
the following 8 steps are possible:
-20, -15, -10, -5, 0, 5, 10, 15 MHz
These steps are controlled by the leftmost frequency selector on the
front panel of the transceiver (0-7). The other two digits are
determined by two crystal banks with 10 crystals each (0-9). The first
one is added in the second mixer, whilst the third one is fed into
a phase discriminator and a differential amplifier followed by a
complex logic circuit that is finally mixed at the heterodyne.
The drawing below shows the wiring of the 7-pin socket marked 'MK.'
at the top right.
It is used for the connection of a handset, headset or another
microphone/speaker combination. The colours are of the internal wiring
when looking into the socket from the front panel of the device.
Connector MK - Handset
BAJ-13,512V (13.5V) rechargeable battery
PT-6Transistorized mains power supply unit (PSU)
MK-1Handset (Mikrotelefonska kombinacija)
AT-17Long rod antenna
AT-19Short rod antanna
ML-6Spinner (for winding wire antenna)
The radio is known under the following names:
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© Crypto Museum. Last changed: Tuesday, 28 September 2021 - 06:30 CET.