HVĚZDA IV 1 , or HVĚZDA 4,
was a portable handheld VHF/FM transceiver
(US: walkie-talkie), developed and built in 1961 in
Správa 6 2 for use in public surveillance tasks, such as with the
Czechoslovakian Border Police. The device works on a single channel
in the 44 MHz band and has a range of approx. 3 km.
It was the first fully transistorized
handheld radio to be used in Czechoslovakia.
HVĚZDA IV is also known by its project designator TI-523.
Although the radio is rather large by today's standards, hardly suitable
for covert operations, it should be considered pretty compact for the era
in which it was developed (1961). Despite the fact that it looks like a bright
green toy, it is a well-designed professional portable radio.
The radio is housed in a bright green plastic enclosure with a large white
grille at the front that covers the speaker/microphone. 3 At the bottom
are two rotary knobs: on for the squelch and one for the volume. The latter is
also the ON/OFF switch (OFF when the red dot is visible).
On top of the device is a
telescopic antenna and a large white Push-To-Talk
(PTT) switch. At the front, just below the large speaker, is the
a large STAR (hvězda) with the number '4' at the center.
The die-cast plastic enclosure is profesionally made, suggesting that the radio
was produced in large quantities. Although it is quite possible that it was
built by a civil company (such as Tesla),
it seems likely that it was built
in-house by Správa 6, the communication technology section of the
Czechoslovakian Government, as indicated by its
HVĚZDA is the Czech word for 'star', hence the star in the logo.
Správa 6 refers to Government Department 6: Communication Technology.
The speaker is also used as a microphone here.
Operating the Hvězda IV is not really rocket science as there aren't many
controls. After installing a fresh set of (12) 1.5V AA-size batteries, the radio
is switched ON by turning the volume knob clockwise away from its OFF position
(the red dot). The radio is now ready for use. If necessary, the squelch knob
can be adjusted to avoid hearing the channel noise. Press the Push-To-Talk (PTT)
button to transmit and speak into the loudspeaker at the front.
Release the PTT to listen.
The radio measures 17 x 9.5 x 4.5 cm, suitable to fit the pocket of, say,
a uniform and weights just 800 gram (batteries included).
Nevertheless, the device was probably carried in the hand, as the
telescopic antenna had to be fully extended for proper operation (±75 cm).
Under normal conditions (10:1 RX:TX), the batteries should last for approx.
The radio is housed in a bright green die-case plastic enclosure that consists
of two shells. The interior can be accessed simply by loosening a single bolt
at the rear side of the case
and taking away the rear shell. The interior also has
to be opened in order to (re)place the twelve batteries.
The front half of the case holds the actual radio and the batteries,
as shown in the image on the right. The compartment at the center contains
a compact PCB assembly with the actual radio.
At both sides of the assembly is space for the batteries:
six 1.5V AA-size cells at the left and another six at the right, delivering
a total of 2 x 9V (or +9 and +18V). When the case is open, the electronics assembly
can be removed without removing any screws:
simply lift the assembly out of the
plastic case shell. It remains connected
to the speaker and the batteries.
After removing the assembly, the telescopic antenna remains behind in the plastic
case shell and does not seem to be connected. Hoever, it is connected to the
transceiver by means of a contact strip at the edge of the assembly.
The frequency appears to be fixed and is noted at the bottom of the device
(channel 20 in this case). Replacing the channel crystal does not seem to be easy.
The radio is built from a mixture of very early NPN and PNP transistors,
mainly made by Tesla,
which is probably the reason for the relatively high battery voltage
that is needed.
It was the first handheld transceiver used by the Czechoslovakian Government that
was fully transistorized. The full
including circuit diagram and PCB layout, can be downloaded below [A].
An interesting feature of this radio is that the transmitter is synchronised
by the receiver, which means that only one crystal in needed for TX
and RX. Hvezda IV is suitable for 43 - 47 MHz.
RX Voltage6.25 - 9V
TX Voltage12.8 - 18V
Weight800 gram (batteries included)
Dimensions43 x 95 x 170 mm
AntennaTelescopic (75 cm)
Temperature-10°C - +40°C
Time10 hours (at 10:1 RX:TX)
RF Output> 100 mW
IF 110.7 MHz
IF 22 MHz
LF output50mW in 300 ohm
RX Transistors9 x OC170, 4 x 107NU70, 1 x OC72, 1 x 101NU71
RX Diodes2 x OA265, 3 x 1NN41
TX Transistors3 x AFY11, 2 x OC170
TX Diodes1 x V39, 1 x Z8
- Popis Přístroje HVĚZDA IV
Original technical description (Czech) with circuit diagrams.
24 February 1962. Scanned from original booklet August 2015.
- Anonymous, Hvězda 4 radio - THANKS!
Devices and documentation kindly donated by anonymous former user. July 2015.
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© Crypto Museum. Created: Saturday 06 August 2016. Last changed: Tuesday, 13 June 2017 - 18:46 CET.