A simple UHF beacon for fox hunt or lost rc model using arduino and 433MHZ rf module

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A simple 433mhz rf module and arduino pro mini as a morse code beacon

In this project a simple 433mhz rf module is used as a uhf beacon for testing purposes. This can be useful in fox hunting (locating hidden transmitter) or for finding lost RC models. An arduino pro mini is used for generating the morse code message, but any avr micro controller can be used.

A simple rf module (with three pins, VCC.GND and ATAD(DATA) is used. It generate an rf signal at 433.9mhz when the ATAD pin is high (so the same pin is connected to pin 13 of the arduino board). A simple firmware will control the pin 13 and hence can send a stored message at frequent intervals.

Wiring is very simple. Connect gnd pin to ground or negative, vcc to 5volt (or higher up to 12v, for better range), and the atad pin to pin 13 of the arduino.

This can be made even simple with an attiny85. Adding a solar charger is another option. If more power is needed, an extra amplifier (uhf ) with a low pass filter can be added. For the antenna i used a piece of wire (17.3cm) but alternatives like a slim jim can be used for better range.

Here is the source code (change the text string to match your need). This will send a morse code message of the text stored. 

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// A simple uhf beacon using 433 mhz rf module // credits to the author of the morse code generator // more details on http://blog.riyas.org struct t_mtab { char c, pat; } ; struct t_mtab morsetab[] = { {'+', 42}, {'-', 97}, {'=', 49}, {'.', 106}, {',', 115}, {'?', 76}, {'/', 41}, {'A', 6}, {'B', 17}, {'C', 21}, {'D', 9}, {'E', 2}, {'F', 20}, {'G', 11}, {'H', 16}, {'I', 4}, {'J', 30}, {'K', 13}, {'L', 18}, {'M', 7}, {'N', 5}, {'O', 15}, {'P', 22}, {'Q', 27}, {'R', 10}, {'S', 8}, {'T', 3}, {'U', 12}, {'V', 24}, {'W', 14}, {'X', 25}, {'Y', 29}, {'Z', 19}, {'1', 62}, {'2', 60}, {'3', 56}, {'4', 48}, {'5', 32}, {'6', 33}, {'7', 35}, {'8', 39}, {'9', 47}, {'0', 63} } ; #define N_MORSE (sizeof(morsetab)/sizeof(morsetab[0])) #define SPEED (13) #define txpin (13) #define DOTLEN (1200/SPEED) #define DASHLEN (3*(1200/SPEED)) void dash() { digitalWrite(txpin, HIGH); delay(DASHLEN); digitalWrite(txpin, LOW); delay(DOTLEN); } void dit() { digitalWrite(txpin, HIGH); delay(DOTLEN); digitalWrite(txpin, LOW); delay(DOTLEN); } void send(char c) { int i ; if (c == ' ') { delay(7*DOTLEN) ; return ; } for (i=0; i<N_MORSE; i++) { if (morsetab[i].c == c) { unsigned char p = morsetab[i].pat ; while (p != 1) { if (p & 1) dash() ; else dit() ; p = p / 2 ; } delay(2*DOTLEN) ; } Serial.print("?") ; } } void sendmsg(char *str) { while (*str) send(*str++) ; } void setup() { pinMode(txpin, OUTPUT); } // the loop void loop() { sendmsg("VVV VVV VVV TESTING TESTING ") ; delay(1500) ; //delay can be increased to save battery }