Samsung UE40ES7000U E-Manual page 760

ΠRadio channels and analogue
broadcasts are not supported.
ΠData broadcast channels are not
supported.
ΠIf the signal is weak or does not
exist, the Timeshift Mode function
will automatically be closed.
ΠTimeshift Mode cannot be performed
if the USB device has no free
memory space. Check that this is not
the case.