Sharp LE820 Instructions Manual page 20

Choose „Test antenna" and the following image will be shown:
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Using the attenuator change the input level of the device, but
during the process observe the „Quality" scale and using the atennuator set
the possibly highest value. It should reach 37-42. A value of over 42 is also
good. While setting quality pay attention to the „Signal strength" scale,
when quality is set at maximum, the value of signal strength shouldn't sink
below 60 (dB), so that also in bad weather the signal is sufficient.
After successful setting errors in reception of HD channels don't appear any
more.
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