Re: measuring radio RF wattage at the antenna

It depends on exactly where you want make the measurement.  If you desire to 
make the measurement BEFORE the RF signal reaches the antenna, then you use 
what is called a power meter or watt meter.  This meter works similar to a volt 
meter; it measures the RF voltage, relative to the impedance of the antenna, 
and displays a reading in watts.  If you desire to make the measurement AFTER 
the RF signal has reached the antenna (i.e., has been transmitted), then you 
can either use a field strength meter or a spectrum analyzer.  The field 
strength meter is used when you are close to the transmitting antenna; it gives 
an indication of the strength (typically on a scale of 1 - 10) of any near-by 
RF signal.  The spectrum analyzer is a sophisticated piece of equipment that 
you use to select a frequency (or a frequency range) to monitor.  The display 
of the analyzer gives a graph and power reading of any signal, within it's 
frequency range and receiver sensitivity range.  The power measurements units 
on a spectrum analyzer are usually decibels (dB).