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Old 16-Sep-2015, 11:44 AM   #3
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,738

Thanks for the tvfool report and more details. I will try to make some useful comments.
I live in Hamilton Ontario. As seen below CHCJ is the one western transmitter I'm after. Its Tx Total distance: 4.49 km (2.79 mi) miles away but the escarpment is 850 meters (Google maps).
On my north are all the Toronto stations; no issue there. I even pick many of those up off the side of my eastern facing two 8 bays
I'm not sure if you know, but there is a Canadian forum with a reception thread for your area. It might be helpful if you also asked about your problem there:
OTA Reception Results

ON - Hamilton, Stoney Creek, Brantford, Haldimand

The first thing I see is that you have two very strong transmitters that might overload your preamp. Fortunately, you picked the 7778 that tolerates overload better than the 7777. Even if the overload is only moderate, the IMD (Intermodulation Distortion) from your two strongest signals can create spurious signals in the preamp that raise the noise floor to damage your weakest signals.

CITS has a Noise Margin of 76.1 dB even before adding the preamp gain.

Interpreting Noise Margin in the TV Fool Report

When I was first learning about Noise Margin, I made this chart to help me understand the concept:

Attached Images
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If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 19-Sep-2015 at 1:19 AM.
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