RF sampling Automatic Band Decoder 0.1-80 MHz


Automatic Band Decoder


This board provides automatic band switching capabilities for LPF and
antenna switches for any radio rig. The main principle is to count the
RF frequency during tuning and use the STM32G CPU as a frequency
counter and switch.

Device works like this:

1. Wait for PTT (GND active) to be activated
2. Once PTT activated, wait for RF to appear
3. Measure incoming RF, AMPL LED lights on a successful measurement
(return to the beginning on error)
4. Set the output according to measured frequency
5. LPF relay activation 10ms time delay
6. Set output PTT (AMPL, GND active)
7. Wait for PTT to be released
8. Go back to waiting for PTT

Board band plan is

1.8-2.0 MHz                  B1
3.5-4.0 MHz                  B2
5.33-5.41 MHz             B3
7.0-7.2 MHz                  B3
10.10-10.15 MHz        B4
14.00-14.35 MHz        B4
18.068-18.168 MHz   B5
21.0-21.45 MHz           B5
24.89-24.99 MHz        B6
28.0-29.7 MHz             B6
50.0-54.0 MHz             B7
69.0-70.5                       B8

There is B* are board outputs, OPEN DRAIN, GND active


Power supply +7-15V, 50mA max
Input RF impedance – >=1 kΩ
Maximum input frequency – 100 MHz
RF Sensitivity – 3V RMS, it is 0.2W RF power at 50 Ohm load
Maximum RF input – 25V RMS, it is 12.5W RF power at 50 Ohm load
Measurement time – 2ms
Number of 50V/100mA outputs – 8
Board sizes 60×50 mm


Additional information

Weight 0.015 kg


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STM32 Band Decoder


Schematic and assembling diagrams