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Old 16-Sep-2016, 3:06 PM   #1
rafaelalbulet
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Do i need a pream for NBC

hi,
can anyone tell me if i need a preamp for NBC.

http://www.tvfool.com/?option=com_wr...e2cb1775d81334
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Old 16-Sep-2016, 4:21 PM   #2
Jake V
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More details, please!

Antenna type (model number), location (roof, attic), direction aimed, how many televisions, length in distance of the coax from antenna to televisions.
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Old 16-Sep-2016, 4:54 PM   #3
rafaelalbulet
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Antenna type (model number) 8 bay antenna, location (roof, attic) roof, 20 ft. above ground,direction aimed CN tower and Buffalo , how many televisions 2, length in distance of the coax from antenna to televisions 40-50 ft.
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Old 16-Sep-2016, 5:21 PM   #4
rabbit73
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Do you get WGRZ NBC now at all?

Your location is not easy for the reception of NBC.

A preamp might help for NBC, but you have some strong local signals that might cause overload.

If you click on Pending in your report, you will see CBLT that is even stronger than CICA.

You could try a preamp that is resistant to overload and aim both of your 8-bay panels at 162 degrees magnetic and hope that the local signals don't cause overload of the amp or the tuner.

WGRZ is 82 miles away and the curvature of the earth will be in the signal path.

The red highlighted "a" next to the WGRZ callsign indicates adjacent channel interference from WNLO that is 29.3 dB stronger than WGRZ. Tuner specs say that WNLO must not be any stronger than 33 db, so I think you are OK.

CBLT has a Noise Margin of 61.1 dB. If you add antenna gain of 12 dB, that brings you up to 73.1 dB, which is overload territory when the antenna is aimed at CBLT.



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

Looking at it from signal power, CBLT -29.7 dBm.

-29.7 dBm = 19.3 dBmV
Max input of CM7778 = 34 dBmV
19.3 dBmV + 12dB ant = 31.3 dB; OK

tuner check
-29.7 dBm + 12 dB ant + 16 dB preamp = -1.7 dBm; slight tuner overload, but the splitter and coax loss might take care of that. If not, you could insert an attenuator to prevent tuner overload.

I think you should try it.
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Last edited by rabbit73; 16-Sep-2016 at 6:19 PM.
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Old 16-Sep-2016, 5:24 PM   #5
rafaelalbulet
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sometimes not all the time
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Old 16-Sep-2016, 7:03 PM   #6
rabbit73
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You are on the fringe for WGRZ



BUT your postal code is in the blue, which is promising

Attached Images
File Type: jpg rafaelalbuletTVFcovWGRZ.JPG (103.0 KB, 399 views)
File Type: jpg rafaelalbuletTVFcovWGRZcu.JPG (85.9 KB, 443 views)
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Old 16-Sep-2016, 7:12 PM   #7
rabbit73
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You have some strong FM signals, if the data is up-to-date, so the FM filter should be IN and the coax should be grounded with a grounding block to reject interference.

http://www.fmfool.com/modeling/tmp/9...2/Radar-FM.png
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Old 16-Sep-2016, 7:53 PM   #8
rabbit73
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This is what the WGRZ terrain profile looks like, showing the curvature of the earth. You can also see how the signal skims the surface just before your location, so any extra antenna height should help especially if there are trees in the signal path.

Attached Images
File Type: jpg rafaelalbuletTVFp2WGRZ.JPG (105.0 KB, 421 views)
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Old 16-Sep-2016, 8:19 PM   #9
Jake V
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I did a generic TV Fool Map for postal code M3A2H1, using no address. The results for 20 feet were not hugely different for WGRZ than your plot:

10 ft = 6.0
20 ft = 8.7
30 ft = 11.5
35 ft = 13.1
40 ft = 14.7

Notice how the signal strength gets better the higher you go. If your roof antenna is 20 above ground than it is likely on a short pole on the roof. You might consider using a longer pole.

That said, I agree with Rabbit. If I were you, the first experiment I would try would be to aim both panels of your 8 bay antenna at 162 degrees (measured with a real compass) and don't touch anything else. While the antenna is aimed at 162 degrees I would check and record the signal strength shown on your tv screen for each channel you receive (assuming your tv displays them). Then post that information here. Each 8 bay antenna has different specs, but I imagine yours would have some decent reception at 45 degrees in either direction of where it is aimed at (for the Toronto stations). It's certainly an easy experiment.
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