Signal Measurement

Hello Everyone.

Firstly I dont know much english… but I have a problem for my thesis.I want to explain to you , maybe you can help about

I did communication system with transmitter-receiver 433 Mhz ( Serial )

in this way…

1 arduino 1 transmitter

void setup()
{
     // Initialise the IO and ISR
    vw_set_ptt_inverted(true); // Required for RF Link module
    vw_setup(2000);                 // Bits per sec
    vw_set_tx_pin(3);                // pin 3 is used as the transmit data out into the TX Link module, change this as per your needs  
}

void loop()
{
    const char *msg = "Community of Robots";       // this is your message to send

   vw_send((uint8_t *)msg, strlen(msg));
   vw_wait_tx();                                          // Wait for message to finish
   delay(200);
}

1 arduino 1 receiver

void setup()
{
    Serial.begin(9600);    

// Initialise the IO and ISR
    vw_set_ptt_inverted(true);    // Required for RX Link Module
    vw_setup(2000);                   // Bits per sec
    vw_set_rx_pin(4);           // We will be receiving on pin 4 i.e the RX pin from the module connects to this pin. 
    vw_rx_start();                      // Start the receiver 
}

void loop()
{
    uint8_t buf[VW_MAX_MESSAGE_LEN];
    uint8_t buflen = VW_MAX_MESSAGE_LEN;

    if (vw_get_message(buf, &buflen)) // check to see if anything has been received
    {
    int i;
     // Message with a good checksum received.
        
    for (i = 0; i < buflen; i++)
    {
        Serial.print(char[i]);                     // the received data is stored in buffer
        }
    Serial.println("");
     }
}

its working serial monitor ‘’ Community of Robots’’

so far everything good and working but I cant measure signal (dB)

reference link

I want to measure the strength of the signal in dB and, I looked in the forum about this topic; Everyone say that ‘’ Xbee ‘’ but I don’t understood for I don’t know much english

How can I measure signal beetween the two arduino ( RF-TX) I think you say that ‘’ RSSI ‘’ and
simply how can I see the distance between two antennas

Thank you for your help ::slight_smile:

You can’t measure the distance or signal strength.
Some of those receiver modules have a digital output and a analog output. The analog output is said to be for the RSSI, but I could not make it work. The Receiver has a AGC (automatic gain control) and amplifies everything (even noise) to a certain level.

This Sparkfun receiver has a RSSI pin, but I have my doubts if that works : RF Link Receiver - 4800bps (315MHz) - WRL-10533 - SparkFun Electronics

Peter_n:
You can’t measure the distance or signal strength.
Some of those receiver modules have a digital output and a analog output. The analog output is said to be for the RSSI, but I could not make it work. The Receiver has a AGC (automatic gain control) and amplifies everything (even noise) to a certain level.

This Sparkfun receiver has a RSSI pin, but I have my doubts if that works : RF Link Receiver - 4800bps (315MHz) - WRL-10533 - SparkFun Electronics

I look thanks peter

in fact I dont need distance but first of all I want to see the power of the signal
and I look forums I have seen a few examples

reference links

http://www.arduino-hacks.com/getting-xbee-rssi-value-using-arduino/

youtube video reference link

You can plug the analog pin from the receiver in an analog pin in Arduino, and then you receive a value between 0 and 1023, this value shows the strenght of the signal.

If you had a precision signal generator you could relate signal strength to RSSI but it would only be valid for that particular setup. In the field with antennas, the RSSI data would be somewhat useless as there are too many parameters affecting the reading. Such things as antennas, orientation, and nearby blockages and reflections are just a few. About all you'll get is strong = close, weak = far or blocked.

On the receivers that do provide a RSSI output, its just a measurement of the AGC voltage
which isnt linear and theres no correlation between the reading and the actual RF input to the receiver.

AGC voltage is a function of signal strength but as you say, "which isnt linear", and somewhat useless without calibration. Signal strength meters derive their info from AGC. In essence, the stronger the signal, the higher the AGC voltage, the lower the IF/RF gain, and the more constant the output.

Technical Description - Third Option