I did mention this already when I came to the idea to use 433MHz HC-12 module for the basic communication. So here we go again, depending on the country you live in it might be required to choose a module with a different frequency or you have to limit the power and usage (duty cycle) of the module to stay within legal usage.
A power level of 4 (6.3 mW / 8dBm) is legal in Gemany on this frequency, and there is no duty cycle limit. Offical document: link: https://data.bundesnetzagentur.de/Bundesnetzagentur/SharedDocs/Downloads/DE/Sachgebiete/Telekommunikation/Unternehmen_Institutionen/Frequenzen/20210114_frequenzplan.pdf
The 6.3mW still allow a distance of 50-80m at 9600baud, using a capacitor even more. This should be enough for the battlefield. If this isn’t enough a step down to 1200 baud will be the solution.
Remember it is not only about being legal, it is also about not annoying other people using the 433MHz frequency too. So be fair and set it down.
#include <SoftwareSerial.h>
SoftwareSerial hc12(13,12); // change the pins to your requirement. I used a D1 mini for the programming.
void setup() {
Serial.begin(9600);
hc12.begin(9600);
Serial.println("use AT+RX to read the settings of the module, use AT+Pn to set the Power of the module where n needs to be replaced by a number between 1 and 8");
}
void loop() {
if (Serial.available()) {
hc12.write(Serial.read());
}
}