2. 5dB antenna either end

If you have a 5dBi gain on both the transmitting and receiving antennas, you would substitute these values 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 distance (d) between the antennas as 1 meter

Now, with 5dBi gain for both the transmitting and receiving antennas (Gt and Gr), the equation becomes:

Pr = 20dBm + 5dBi + 5dBi + 20log10(0.125/4π*1) = 20dBm + 10dB - 47.55dB = -17.55dBm

So, the received power would be around -17.55dBm. This value can be converted back to milliwatts using the formula Power (in mW) = 10^(Pr/10), which results in approximately 0.018mW.

To convert milliwatts (mW) to microwatts (μW), you multiply the number of milliwatts by 1000, as there are 1000 microwatts in a milliwatt.

So, 0.018 mW is equal to 0.018 * 1000 = 18 μW.

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.

Yes that is 18µW!! What can you do with 18 micro watts?

2 meters away this becomes: which results in approximately 0.0088mW or 8.8μW.