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.
If it doesn't seem to be zero, there's something wrong with your
measurement system.
Roy Lewallen, W7EL
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