RA3WDK `s Homepage

RF & Nf Measurement


Two Tone TEST Generator 14 MHz for test the quality of

receiver by injecting two non-harmonic tones near 14400 kHz

To determine the IP3 (Intercept Point of 3rd order Intermodulation Products) a 2-tone RF generator is required for providing two signals of equal amplitude with low frequency spacing. Typically, in many measuring devices a signal spacing of 20 kHz is used. I made only 400 Hz for easy measure by SoundCard in 3 kHz bandwidth.

The level of intermodulation products of third order (IMP3) of FSVA40 about 91,5 db




    Noise figure is a one of main performance parameter for HAM VHF/UHF/SHF systems. A low noise figure provides improved signal/noise ratio (SNR) for our EME/MS setup. If you want to try make good low-noise amplifier (LNA) - you must improve noise figure measurement accuracy. Is this easy work ? But we can do it !

    I use the Y-factor method with different noise source : Home made source (p-n channel or diode), industrial noise source, "cold" horn.

Fundamentals TRX system = THOT(1/(Y-1)) - TCOLD(Y/(Y-1))

Fixing Measurement Errors

1. Use big difference between THOT and TCOLD . ENR must be more than 10-15 db

2. Use attenuator 10-20 db between source and LNA, because that S11 of source or LNA not optimal (SWR=1)

3. Use broadband IF section before the detector, but use IF section with Quality Band Pass Filter (BPF).

4. IF section must have good perfomance IP1 , IP3

5. Detector must have stability and accuracy more than 0,05-0,1 db in band 20-25 db


You can download NF calculator - NoiseFigure_v4.xls

Meter for measurment Noise of Moon and Sun

Digital Noise Meter

Noise Meter uses Log.Detector AD8307 , ADC by MCU ATmega16, Precision voltage regulator LM4040A, thermometer DS18D20 in noise source

IF section 28 MHz


"Cold" horn for measurement Noise factor of LNA on 5,7 Ghz and 10 Ghz



Measure NF my 1296 MHz system



Look here my new idea ! Noise tester for test HF-VHF transceivers.

You need only connect 9V battery to Noise Tester in PL-259 connector and you see in S-metr S 6-7 from 160 to 2 meters !

PreAmpAD8129 PreAmpAD8129