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#### cliffliu

##### Junior Member level 3 My link budget sheet is using noise figure but the radio receivier capability specification are SINAD of unit.
How to transform SINAD into noise figure?
Thanks

#### John_li

##### Full Member level 5 First transform 0.18uV into dBm,and use the following equation to transform:
Pin(0.18uV------>dBm)+174dBm/Hz-12-10logB=NF(dBm)
B-----the bandwidth.
cliffliu said:
My link budget sheet is using noise figure but the radio receivier capability specification are SINAD of unit.
How to transform SINAD into noise figure?
Thanks

#### cliffliu

##### Junior Member level 3 My radio each channel is 25KHz.
10*log(((0.18uV * 0.001)^2)/50)= -91.88dBm
NF= -91.88dBm + 174dBm/Hz -12dB -10*log(25KHz)= 26.14dB
Correct?
And then,
Why BW in dB is 10*log(BW)? Not 20*log(BW)?

Thanks you!

#### vfone Conversion uV to dBm in 50ohms is:
10*LOG(((uV/1000000)^2)/50)+30 = dBm
Sensitivity = 0.18uV = -121.9dBm

The S/N ratio required at the input of a detector depends on the particular measure of receiver sensitivity. For example 12dB SINAD (audio measurement) may require 5dB S/N ratio at detector IF frequency.

NF(dB) = Sensitivity(dBm) + 174 – 10*LOG(BW in Hz) – S/N =
= -121.9 + 174 – 43.97 – 5 = 3.1dB

#### John_li

##### Full Member level 5 for Pin=Ps*B Ps:dBm/Hz transform into dBm,you will get the equation:10*log(BW) not 20log(BW)
cliffliu said:
My radio each channel is 25KHz.
10*log(((0.18uV * 0.001)^2)/50)= -91.88dBm
NF= -91.88dBm + 174dBm/Hz -12dB -10*log(25KHz)= 26.14dB
Correct?
And then,
Why BW in dB is 10*log(BW)? Not 20*log(BW)?

Thanks you!

#### cliffliu

##### Junior Member level 3 vfone said:
The S/N ratio required at the input of a detector depends on the particular measure of receiver sensitivity. For example 12dB SINAD (audio measurement) may require 5dB S/N ratio at detector IF frequency.

NF(dB) = Sensitivity(dBm) + 174 – 10*LOG(BW in Hz) – S/N =
= -121.9 + 174 – 43.97 – 5 = 3.1dB
Does the S/N required will present on radio specification?
Will be testing on each radio if we want to know the radio S/N?
Or, the 5dB S/N is a general specification.

Thank you!

#### vfone S/N at the input of the detector is a general specification and is part of the RF system analysis.

#### spide

##### Member level 3 can anyone guide me how to obtain the S/N for FM and how to calculate the distortion of 25% for a given 12dB SINAD.

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