bladeRF with Linrad on 432 MHz. A single carrier at different levels.

bladeRF with Linrad on 432 MHz. A single carrier at different levels.
(Dec23 2013)

This page is a sub-page to bladeRF with Linrad on 432 MHz.

The images show the observed spectrum at different signal levels. The signal levels are given in dBm as indicated on the signal generator, but there are some cable losses so the level at the bladeRF input connector is a little lower.

Fig. 1. The generator is set to -30 dBm. This is about 2 dB from saturation. The center frequency is 431.75 so the fundamental in the baseband is 260 kHz. High order harmonics of 260 kHz have an appearent level of about -70 dBm to -80 dBm.

Fig. 2. The generator is set to -40 dBm. This is about 12 dB from saturation. Compared to figure 1 the high order harmonics of 260 kHz are weaker, but the low order harmonics are stronger. The second harmonic is only about 30 dB below the fundamental.

Fig. 3. The generator is set to -50 dBm. This is about 22 dB from saturation. Harmonics are still pretty strong.

Fig. 4. The generator is set to -60 dBm. This is about 32 dB from saturation. High order harmonics are almost gone, but the second harmonic is only about 40 dB below the signal.

Fig. 5. The generator is set to -70 dBm. This is about 42 dB from saturation. The second harmonic is still well visible.

Fig. 6. The generator is set to -80 dBm. This is about 52 dB from saturation. The second harmonic is still well visible.

Fig. 7. The generator is set to -90 dBm. This is about 62 dB from saturation. No harmonics are visible at this level.

Fig. 8. The generator is set to -100 dBm. This is about 72 dB from saturation. The signal is still well above the noise in the 1 kHz wide baseband filter. The 10 dB step from -60 to -70 in the S-meter window shows this.

Fig. 9. The generator is set to -110 dBm. This is about 82 dB from saturation. The signal is still well above the noise in the 1 kHz wide baseband filter. The 10 dB step from -70 to -80 in the S-meter window shows this. The noise floor does however contribute a little to the S-meter graph at the -80 level.

Fig. 10. The generator is set to -120 dBm. This is about 92 dB from saturation. At -90 the noise contributes nearly 1 dB.

Fig. 11. The generator is set to -130 dBm. This is about 102 dB from saturation. At -100 the noise contributes about 5 dB which means that the noise is stronger than the signal.

Fig. 11. The generator is set to OFF. The noise floor is 97 dB below the maximum signal 2 dB below saturation. This sets a maximum limit for the dynamic range at 138 dBc/Hz with the usual definition of having the carrier 1 dB below saturation. Reciprocal mixing will reduce the dynamic range depending on the frequency separation.

With a selective amplifier having a low NF and with enough gain to lift the noise floor by 15 dB, the limit for the dynamic range would be 123 dBc/Hz with a noise figure only 0.13 dB worse than the NF of the selective amplifier. At close range, 20 kHz, the dynamic range is limited to about 100 dBc/Hz due to reciprocal mixing. To reach 123dBc one needs a frequency separation of about 300 kHz. For details see bladeRF with Linrad on 432 MHz.