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NF and Gain Measurement Using SA & Noise Source - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement

Post subject: NF and Gain Measurement using SA & Noise Source
Unread postPosted: Sun Jul 11, 2004 5:38 pm

Please help me to Measure LNA NF & Gain using Spectrum Analyzer & Noise Source


Kirt Blattenberger
Post subject:
Unread postPosted: Tue Jul 13, 2004 12:51 pm
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Agilent has an application note for that here:

Spectrum Analyzer Measurements and Noise
Application Note 1303 ... -4008E.pdf

- Kirt Blattenberger :smt024


Post subject: Using Noise generator for NF measurement
Unread postPosted: Tue Dec 14, 2004 9:30 pm

Sorry the Agilent app note referenced in the other reply will not help you .
see instead /5952-3706E.pdf.

You need to set your spec. an. to work as a RF power meter.

1. Set IF bandwidth high as you dare.
2. Set Video filter as low as you have time to wait for trace.
3. Set to 1 dB/ div or if youre lucky use a maker at the centre of your noise.
4. You will need a low noise preamp if the gain of your device or system (DUT) is gain is less than about 20dB.
5. Check for this - the noise level should drop by at least 10dB when you disconnect or power down your DUT.
6. If not use minicircuits or other gain block amplifier to get result 5.
super low noise not required about 4dB is OK.
7. Connect noise generator to DUT. switch on, your spec an noise should jump at least 3dB.
8. Apply Y factor formula to calculate result from generator ENR, ambient temp (ussually assumed), and change in spec. an. dB reading noise generator off to on. Y is this dB reading converted to a straight power ratio
9. Y factor method formulas are on the net see /5952-3706E.pdf

Posted  11/12/2012

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