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Old 20-Mar-2017, 2:35 AM   #9
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,550
Antennas

The Antennas Direct 91XG was not rescaled for the 14-51 UHF band, but the DB8E was rescaled to improve the gain at the low end.



The 91XG and the HDB91X yagis have a tilt feature built in, but the DB8E does not; it would be a custom mod. I have received several reports from people who were located behind a hill and have used the tilt feature; they were able to receive channels that were impossible before tilting the antenna.

The only way you can do better with an antenna is with a custom designed yagi for channel 15.

It is impossible to receive signals weaker than NM -15 dB because they are buried in the Thermal Noise Floor below -106 dBm. If you are able to receive channels listed below -15 dB NM, either the tvfool report is wrong or the signal has been enhanced by Tropospheric Propagation.



Here is the System Noise Figure calculation for the above diagram:



You can do a little better if you use a preamp with a lower noise figure and a lower loss balun:



Yes, the KT-200 would also be my choice. Keep in mind that the ultra low noise preamps are more sensitive to static damage; that's the trade-off. The Antennas Direct PA-18 might be a good compromise design for your location, but you haven't told us which CM preamp you are using.

I second the suggestion to use the best tuner you can find; they do vary in sensitivity.
Attached Images
File Type: jpg AD 91XG Gain vs Freq.JPG (124.1 KB, 5392 views)
File Type: png SysNFDX2.PNG (34.7 KB, 1104 views)
File Type: jpg Preamp (2).jpg (363.7 KB, 176 views)
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Last edited by rabbit73; 21-Mar-2017 at 3:02 PM.
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