[rabbit73]

Originally Posted by WIRELESS ENGINEER

If you get the other 49 channels then there is no reason

I agree. If you get 49.1, you should be getting 49.5 and 49.6.

Since most TVs deal with cable signal levels of 0 to +15 db without issue, I don't think this is an overload issue

You haven't stated the units, but you probably mean dBmV.

Yes, that is a good range for the input at the tuner, but his signals on his report are much stronger than that. The tvfool report assumes that the antenna is outside and in the clear. His antenna is in the attic and many trees are in the signal path. Now that he has told us about the trees (and I have seen the trees in a satellite view of his area), I am beginning to think it might NOT be an overload problem.

WHRO has a Noise Margin of 71.4 dB. If you add an antenna gain of 12 dB, that brings you up to 83.4 dB NM which is overload territory IF the antenna is outside and in the clear. But, his antenna is in the attic and there are trees in the signal path that can attenuate the signals.



Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html

WHRO has a signal power of -19.4 dBm (+29.6 dBmV). If you add the antenna gain, that brings you up to -7.4 dBm (+41.6 dBmV) which is tuner overload.

ATSC Recommended Practice:
Receiver Performance Guidelines

Document A/74:2010, 7 April 2010

RECEIVER PERFORMANCE GUIDELINES

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.

When there are more than Two Strong Input Signals:
Max Signal Input would need to be DERATED:
3 Signals: -3.6 dB
4 Signals: -5 dB
5 Signals: -6 dB
6 Signals: -7 dB
8 Signals: -8 dB
Ignore signals more than 6 dB below the Strongest.

In this case, signals stronger than -16 dBm (+33 dBmV) risk tuner overload. I have no idea how strong the signals are coming out of the 4221HD antenna in the attic, because the attenuation from the trees and the attic are unknown.