LNA noise figure measurement Y factor method vs other methods

Y factor method appears to be a popular way to measure the noise figure of a LNA. But there are alot of steps required to obtain the answer.

By definition the Noise Figure = 10 log (SNRin/SNRout)

My question is why go through all the elaborate setup in the Y factor method of obtaining the noise figure of the LNA when you can just measure the SNR at the input of the LNA and then measure the SNR input of the LNA at the output?

Is it acceptable to obtain the noise figure of the LNA by just measuring the SNR in and SNR out of the LNA instead of going through all the hassle of the Y factor method?

You can use any suitable method to determine your LNA's NF. The difficult part is to measure INPUT S/N as the bandwidth must be well defined and as the noise level is very low there, it is technically difficult to measure it.

The Y-factor method is the easiest one as you need a good receiver (or RF amplifier) with a 30-40 dB gain, and a power meter. By connecting your LNA to receiver input and by applying two defined noise input levels (like the ambient and either a higher or a lower one), from the power ratio you can easily calculate the LNA NF.

If you happen to have a controllable noise generator, you can use the "Twice output power" method.

All commercial NF meters utilize the Y-factor method as it is the easiest and most accurate one. Usually a calibrated noise source is used with it that covers your RF frequency range. Bu going through the "hassle" you get good results (and reverse).

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The Y-factor method is the easiest one as you need a good receiver (or RF amplifier) with a 30-40 dB gain, and a power meter. By connecting your LNA to receiver input and by applying two defined noise input levels (like the ambient and either a higher or a lower one), from the power ratio you can easily calculate the LNA NF.
[/QUOTE]

In regards to The Y-factor method. I used a manual from rohde-schwarz to help me understand how to measure NF.

http://www2.rohde-schwarz.com/file_15856/1MA178_0E.pdf

I noticed throughout the document there is no reference to frequency. Isn't the NF calculation contingent upon frequency?

The NF CALCULATION does not depend on frequency, but receiver components as well as noise sources are frequency dependent.