RTL-SDR Rx AIS Power Calibration – Telecommunications, Navigation & Electronics

Introduction

Several years ago I looked at calibrating the RTL-SDR receive level in dBm in connection with LoRa transmission (Ref.1). The same can be done for receive levels for AIS. In my last post I looked at AIS reception from my new QTH along with signal levels (Ref.2).

Measurement Setup

Fig.1 RTL-SDR AIS Power Calibration Setup

Fig.2 GNU Radio Schematic for PlutoSDR SigGen 162MHz

Fig.3 PlutoSDR Tx_gain = 89 Rx = -1.6dBm (-21.55+20pad) at 162MHz

GNURC Tx Level	SigHound Rx Level	Gqrx Rx Level 19.6dB Gain	Gqrx Rx Level 29.6dB Gain
89	-1.6dBm
20	-69dBm	-25dB	-15dB
15	-74dBm	-30dB	-20dB
10	-79dBm	-35dB	-25dB
5	-84dBm	-40dB	-30dB
2	-87dBm	-43dB	-33dB

Fig.4 RTL-SDR Rx Power Calibration Table

Figure 1 shows the measurement setup and Figure 2 shows the GNURC schematic used to drive the PlutoSDR signal generator at 162MHz. Figure 3 shows the Spectrum Analyzer receive level for maximum transmit. Figure 4 shows the Gqrx receive levels at two different gains for a given transmit dBm. Gqrx and SDR# levels were similar.

Local Carrier Reference

Fig.5 Spike STL Carrier 152.090MHz Rx Level = -79dBm

Fig.6 Gqrx STL Carrier 152.090MHz Rx Level = -35dB Gain at 29.6dB

Previously I used Toronto Marine Weather at 162.4MHz as a local carrier reference. This is gone now, however I found a carrier close by at 152.090MHz (Bell Media STL for Pulse 24 News). This measured at -79dBm on the Spectrum Analyzer and -35dB on Gqrx.

Fig.7 YouTube Video RTL-SDR Rx AIS Power Calibration

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References

#1. – “RTL-SDR Rx Power Calibration”
https://jeremyclark.ca/wp/telecom/rtl-sdr-rx-power-calibration/

#2. – “AIS on RaspberryPi4 QTH+”
https://jeremyclark.ca/wp/telecom/ais-on-raspberrypi4-qth/

Introduction

Measurement Setup

Local Carrier Reference

References

By Jeremy Clark