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Turns out my new model CM7777 pre-amp is actually fine. Raising the antennas higher caused the signal level to go high enough that it got swamped out. I'll keep it for a spare, and use attenuators in front of it if need be.
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Interesting; I did not consider that, but it makes sense. WNEM is listed as -43.0 dBm signal PWR for an antenna in the clear. If you add the antenna gain of at least 10 dBd, that brings you up to -33 dBm. If you then add the 30 dB preamp gain you are at -3 dBm which makes preamp and tuner overload probable.
ATSC Recommended Practice:
Receiver Performance Guidelines
Document A/74:2010, 7 April 2010
RECEIVER PERFORMANCE GUIDELINES
5.1 Sensitivity
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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.
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5.2 Multi-Signal Overload
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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.
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Looking at it from the standpoint of Noise Margin, WNEM is 47.9 dB. If you add the antenna gain and the preamp gain, you are at 87.9 dB which is definitely Overload territory.
Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html
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Then maybe I'll try going after WUWB-20 again at an NM of 5.3 with a separate HDB91x antenna. That might be pushing it due to trees that way, but I can get WCMZ-28 solid at 62% on the main antenna at NM 5.8, and it has just as many trees that way. If I can get that channel 20 to lock, I'll have to get an AC7-CH.20U from Tin Lee and then try joining to the main system. I emailed them for a price quote, but no reply so far.
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Uh-Oh. You are turning into a dedicated antenna experimenter who wants "just one more channel."
