"Roy Lewallen" wrote
The average value of a signal is its DC value. To receive and reproduce a
signal with a non-zero DC component means that your antenna, as well as
your receiver, has to have response to DC. To generate such a signal would
require a static electric and/or magnetic field, which can't propagate. So
it's not possible for a signal you're receiving to have a non-zero average
value.
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Pure DC doesn't radiate, but there can be a DC component in the modulation
of an RF wave that does radiate. An example is analog broadcast television,
which has a highly asymmetric RF waveform. It can transmit a constant (DC)
video value of any amplitude between reference black at 75% modulation and
reference white at 12-1/2% modulation.

RF