Hi Hank, A 1/2 wave shorted stub looks like a series resonant circuit.
It
makes a good notch filter, which is one of the Amateur applications that I
have
used. You are right, they don't dissipate any power since Power=I**2*R
and R
equals zero.

73 Gary N4AST
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R is not zero. It can be several ohms. And lots of amps can flow.

Just to add a 1/2-wave shorted stub also makes a mess of the tuning of the
remainder of the antenna system at all other frequencies. It must be
designed "in".