3. 10 meters away from the source

If you move to 10 meters away from the source, you substitute this new distance into the Friis Transmission Equation:

Pr = Pt + Gt + Gr + 20log10(λ/4πd)

We previously calculated:

    • The transmitted power (Pt) as 20dBm

    • The wavelength (λ) as approximately 0.125 meters

    • The gains of the transmitting and receiving antennas (Gt and Gr) as 5dBi each

Now, the distance (d) between the antennas becomes 10 meters:

Pr = 20dBm + 5dBi + 5dBi + 20log10(0.125/4π*10) = 20dBm + 10dB - 60dB = -30dBm

So, the received power would be around -30dBm. This value can be converted back to milliwatts using the formula Power (in mW) = 10^(Pr/10), which results in approximately 0.001mW or 1μW.

Once again, this is a theoretical calculation. In a practical scenario, you may receive more or less power due to factors such as obstructions, antenna patterns, interference, and other complexities of radio wave propagation. Your receiver also needs to be capable of receiving at such low power levels.