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Old 2-Oct-2016, 6:47 PM   #26
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,569
WDIV on real channel 45 has adjacent channel interference from WUPW on real channel 46. A tuner is not expected to reject adjacent channel interference that is more than 33 dB stronger. WUPW is 49.6 dB stronger than WDIV.

5.4.2 Adjacent Channel Rejection

The receiver should meet or exceed the thresholds given in Table 5.2 for rejection of first
adjacent-channel interference at the desired signal levels shown above the columns therein.

When you overload a tuner with local signals, it makes reception of weaker signals more difficult, because spurious signals are created in the tuner from IMD (Intermodulation Distortion) that damage the weak signals.

WUPW -29.1 dBm + 13 dB ant + 18 dB preamp = +1.9 dBm; tuner overload

ATSC Recommended Practice:
Receiver Performance Guidelines

Document A/74:2010, 7 April 2010


5.1 Sensitivity

A DTV receiver should achieve a bit error rate in the transport stream of no worse than 3x10E-6 (i.e., the FCC Advisory Committee on Advanced Television Service, ACATS, Threshold of Visibility, TOV) for input RF signal levels directly to the tuner from –83 dBm to –5 dBm for both the VHF and UHF bands.
5.2 Multi-Signal Overload

The DTV receiver should accommodate more than one undesired, high-level, NSTC or DTV signal at its input, received from transmission facilities that are in close proximity to one another. For purposes of this guideline, it should be assumed that multiple signals, each approaching –8 dBm, will exist at the input of the receiver.
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2-Oct-2016 at 7:22 PM.
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