S/N AT DIFFERENT SIGNAL LEVELS IN NF MEASUREMENTS WITH LINRAD.
(Sept 3 2012)
This page is a sub-page to PRECISION MEASUREMENTS OF NOISE FIGURES.

The images below show the Linrad screen at different signal levels. Data extracted is listed in table 1.

The below images are produced one after the other and what happens at high levels is well visible in the waterfalls and in the wideband graph. 

Level   (Sb+Nb)/Nb     (Sb+Nb)/Nw        Error
(dBm)      (dB)          (dB)     (dB or comment)
 off        0             0
 -55       24.57        0.07      (level too low)       
 -45       34.60        0.068        nearly OK
 -35       44.63        0.068           OK
 -25       54.61        0.068           OK
 -15       64.63        0.062           OK
 -5        74.57        0.059         0.005
  5        84.73        0.008         0.060
 15        94.48       -0.345         0.413
 Table 1. Data extracted from the figures below.

Figure 1. The signal is switched off.

Figure 2. The signal level is -55 dBm.

Figure 3. The signal level is -45 dBm.

Figure 4. The signal level is -35 dBm.

Figure 5. The signal level is -25 dBm.

Figure 6. The signal level is -15 dBm.

Figure 7. The signal level is -5 dBm.

Figure 8. The signal level is +5 dBm.

Figure 9. The signal level is +15 dBm.