Thread: Noise Threshold
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Old 24-Jan-2016, 3:02 AM   #7
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,565
Here are two Noise Margin diagrams of an indoor antenna without preamp. They are two versions of the same setup. Version 1 is the way Andy shows it with the minimum required SNR added to the thermal noise floor and then the tuner NF is added to that. Version 2 adds the tuner NF to the thermal noise floor and then the minimum required SNR is added to that, showing what goes on between NM 0/-91 dBm and the thermal noise floor at -106 dBm. Note that a signal stronger than NM 0 dB, namely NM +6 dB in this case, is needed at the input of the tuner to offset the 6 dB NF of the tuner.

Attached Images
File Type: png NMdiagIndoorV1rev.PNG (44.3 KB, 2775 views)
File Type: png NMdiagIndoorV2rev.PNG (44.6 KB, 2749 views)
File Type: png NetNMV1V2.PNG (41.3 KB, 4977 views)
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 11-Sep-2017 at 11:00 PM.
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