TUNIT - Universal Tuning Unit

TUNIT is the universal tuning unit, suitable for tune-circuits in receivers and transmitters. The base circuit "Voltage Variator" was given the Czech Author`s Certificate No.209017 back in 1981. The authors are Karel Pazdernik and Petr Prause. A capacitor with minimal leakage is the heart of this circuit. It is charged and discharged by the push-switches, connected by the different value resistors at the entry of the JFET op-amplifier.

The analog indicator of the tune voltage can be used as the frequency dial. It can be used for other functions too, for example: for antenna current measuring in the transmittion mode.

The "TUNIT" tuning has an advantage over a synthesized frequency centre by having a simple connection and complete absence of disturbing frequency spectrum. Therefore it is very suitable for simple QRP equipments.

The basic connection of TUNIT.

The 6-speed TUNIT 1980.
The N-FET KF521 and op-amp LM741 were used. Capacitor is REMIX C213, 4uF, 63V.
Analog indicator was in the neverfinished transceiver.

Base circuit of TUNIT was later widespreaded
for setting the range and speed of automatic changes of frequency in both directions.

Tuning Unit TUNIT was developed
in the RadioLab of Q-club. July 2002.

TUNIT 2002, the inside-look.

TUNIT 2002 in the experimental operation,
a module part of the QRP complex OK1DPX.

Finished TUNIT 2002, with the front panel.
On top is analog indicator, below it is AUT-MAN switch, below it are four manual-tuning push-buttons. In the middle of the push-buttons is a separator to easy control. The upper two knobs are the speed selectors for automatical tuning in both directions, the two bottom knobs are to set the high and low end of tuning.