Foundations Of Amateur Radio

Foundations of Amateur Radio Recently I explained some of the reasons why I've shifted to using dBm to discuss power. You might recall that 1 Watt is defined as 1,000 mW and that's represented by 30 dBm. 10 Watts is 40 dBm, 400 Watts, the maximum power output in Australia is 56 dBm and 1,500 Watts, the maximum in the USA, is just under 62 dBm. My favourite power level, 5 Watts, is 37 dBm. I mentioned that using dBm allows us to create a continuous scale between the transmitted power and the received signal. On HF, an S9 report is defined as -73 dBm. Between each S-point lies 6 dB, so an S8 signal is -79 dBm, S7 is -85 dBm and so-on to S0, which is -127 dBm. Said differently, to increase the received signal by one S-point you need to quadruple the power output. Now, let's consider a contact with a 100 Watt station, 50 dBm. Let's imagine that the receiver reports an S8 signal. That means that between a transmitter output of 50 dBm and the received signal at -79 dBm, there's a loss of 129 dB. If we dial the p