ARRL, RSGB and other books will show you how to make radio things.

Good RF designers can think up new radios and/or aerials and make them work.

But I suspect that no-one actually knows how "radio" (or IR or Light, 
all same stuff apparently)  actually  works.

There are theories and  formulas that make  it possible to design  
Wireless Sets and  Aerials.

An aerial (wire(s), pin in waveguide, square pad on PCB over a ground 
plane) of suitable dimensions connects to an AC signal and the signal in 
the wiring becomes "waves" in air or vacuum. There is poor penetration 
of liquids and solids, but some.

Below 500kHz it's difficult to have much efficiency in the conversion 
process from wires to wave. A 137kHz transmitter with 2kW of power might 
only result in 1W of RF waves if an aerial is only 20meters long.  At 
10Ghz, you might get over 90% of your electrical energy turned into 
radio waves by a connector pin the correct length in a 3/4" copper water 
pipe used as a waveguide.

Anyone that thinks they *REALLY* understand radio is not an expert.


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