FS1000A transmits more reliably when holding wire

Hello all,

I’m currently trying to use a FS1000A and a RXB6 to send a message from one UNO to another. Both transmitter and receiver are connected with soldered wires. When both modules are lying on my table, they sometimes transmit data reliably, but mostly not. However, when I touch the ground wire of the transmitter, it starts to transmit far more consistently and reliably. I have not connected an antenna to either of the modules. Is it just a bad solder connection or is it something else?

Here’s the transmitter code:

#include <VirtualWire.h>
void setup()
{
    Serial.begin(9600);   // Debugging only
    Serial.println("setup");
    vw_set_tx_pin(3);
    // Initialise the IO and ISR
    vw_setup(2000);      // Bits per sec
}
void loop()
{
    const char *msg = "hello";
    digitalWrite(13, true); // Flash a light to show transmitting
    vw_send((uint8_t *)msg, strlen(msg));
    vw_wait_tx(); // Wait until the whole message is gone
    digitalWrite(13, false);
    delay(200);
}

And here’s the receiver code, just in case:

#include <VirtualWire.h>
void setup()
{
    Serial.begin(9600); // Debugging only
    Serial.println("setup");
    // Initialise the IO and ISR
    vw_set_rx_pin(2);
    vw_setup(2000);      // Bits per sec
    vw_rx_start();       // Start the receiver PLL running
}
void loop()
{
    uint8_t buf[VW_MAX_MESSAGE_LEN];
    uint8_t buflen = VW_MAX_MESSAGE_LEN;
    if (vw_get_message(buf, &buflen)) // Non-blocking
    {
        int i;
        digitalWrite(13, true); // Flash a light to show received good message
        // Message with a good checksum received, dump it.
        Serial.print("Got: ");
        
        for (i = 0; i < buflen; i++)
        {
            Serial.print(buf[i], HEX);
            Serial.print(" ");
        }
        Serial.println("");
        digitalWrite(13, false);
    }
}

The code is simply the VirtualWire example code adapted to my setup. It is highly unlikely that the fault lies in the code, however, as the same issue arises with different sketches.

How are things actually wired up, a sketch of the wiring and a photo of the units on the table might help.
Given this appears to be your first post well done for using code tags and supplying all the code.

A balanced dipole antenna works extremely well with those modules, shown in the photo below. The connection labelled GND is actually the other antenna connection!

The antenna wires are each 17 cm long for 433 MHz. I get over 300 meters range, line of sight with the setup shown.

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