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HVĚZDA IV   TI-523
Handheld transceiver

HVĚZDA IV 1 , or HVĚZDA 4, was a portable handheld VHF/FM transceiver (US: walkie-talkie), developed and built in 1961 in Czechoslovakia by 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).
  
HVEZDA 4 handheld radio

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 logo: 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 project number.
 
  1. HVĚZDA is the Czech word for 'star', hence the star in the logo.
  2. Správa 6 refers to Government Department 6: Communication Technology.
  3. The speaker is also used as a microphone here.

Pair of HVEZDA 4 handheld radios HVEZDA 4 handheld radio HVEZDA 4 handheld radio Telescopic antenna and PTT Operating the PTT Star-logo and two potentiometers Adjusting the volume Knobs and serial number tag

 
Controls
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. 10 hours.
 
Interior
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.
  
Rear panel removed

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 technical description, 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.
 
Rear side Rear panel removed Removing the PCB from the case PCB assembly removed from the case Close-up of the PCB assembly Top side of the PCB assembly PTT detail Electronics detail

 
Specifications
  • Modulation
    FM (F3)
  • Channels
    1
  • Power supply
    Batteries
  • Voltage
    18V, 60mA
  • RX Voltage
    6.25 - 9V
  • TX Voltage
    12.8 - 18V
  • Weight
    800 gram (batteries included)
  • Dimensions
    43 x 95 x 170 mm
  • Antenna
    Telescopic (75 cm)
  • Temperature
    -10°C - +40C
  • Time
    10 hours (at 10:1 RX:TX)
  • RF Output
    > 100 mW
  • Impedance
    150 ohm
  • Sensitivity
    1.5µV
  • Selectivity
    80dB
  • IF 1
    10.7 MHz
  • IF 2
    2 MHz
  • LF output
    50mW in 300 ohm
  • RX Transistors
    9 x OC170, 4 x 107NU70, 1 x OC72, 1 x 101NU71
  • RX Diodes
    2 x OA265, 3 x 1NN41
  • TX Transistors
    3 x AFY11, 2 x OC170
  • TX Diodes
    1 x V39, 1 x Z8
Documentation
  1. Popis Přístroje HVĚZDA IV
    Original technical description (Czech) with circuit diagrams.
    24 February 1962. Scanned from original booklet August 2015.

References
  1. Anonymous, Hvězda 4 radio - THANKS!
    Devices and documentation kindly donated by anonymous former user. July 2015.

Further information

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Crypto Museum. Created: Saturday 06 August 2016. Last changed: Friday, 22 July 2016 - 13:52 CET.
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