This internal automatic antenna tuner is designed specifically for mcHF SDR radio.

You can install this autotuner to mcHF SDR radio with RF PCB versions: 0.4, 0.5, 0.6, 0.6.1, 0.6.2, 0.6.3 and RS-918 clones.

For check possibilities of installation to another versions of RF PCB, please send me good photo of your RF PCB

This autotuner have low profile and fit well in Chinese case for mcHF SDR radio.

Due to use of latching relays, the autotuner consumes energy only at the time of tuning.

Power consumption of the autotuner is about 35 mA for 5V.

After completing the tuning process, the autotuner turns off.

mcHF AT Schematic.pdf

Autotuner built by 5x5 schematic:

- 5 inductances (T37 core): 0.1, 0.22, 0.45, 1 and 2.2 mH;

- 5 capacitors (high voltage): 10, 22, 47, 100 and 220 pF;

- 11 latching relays (IM43);

- ATmega328 as controller and some smd parts.

An approximate range of complex impedance, that the autotuner can match by bands, you can see at the picture: