RTL-SDR for Satellite Weather on GOES16 – Planning – Telecommunications, Navigation & Electronics

Introduction

In previous posts we looked at receiving weather information via HFWEFAX (Ref.1) and GRIB files (Ref.2) over an internet connection. In the next several posts, we will examine receiving weather information directly from a geostationary satellite GOES16(R) and see if it is suitable in a marine application for solo/family blue water sailors. My thanks to Yves_First42s7 for suggesting this topic.

Geostationary Weather Satellites

Country	Satellite Name	Longitude
United States	GOES16(R) Atlantic Ocean	75.2degW
	GOES17 Pacific Ocean	137.2degW
Russia	Electro-L No.1 Indian Ocean	76degE
Japan	MTSAT-2 Himawari Pacific Ocean	145degE 140degE
Europe	Meteosat 6/7/8/9	63degE, 57.5degE 3.5degW, 0degW
China	Fengyun FY-2E/2F/2G/4A	86.5degE, 123.5degE 105degE, 104.5degE
India	INSAT 11 operational	74degE – 93.5degE

Table 1 Geostationary Weather Satellites (Ref.3)

GOES16(R) Signal & Freq	Signal Parameters
GRB Rebroadcast 1686.6MHz L Band Dual Circular Polarization	QPSK DVB-S2 @ 8.665938Msps 15.5Mbps Coder Opt 60.5dBmi at Sat edge footprint 9/10 rate + BCH coding SRRC filter alpha=0.25 NRZ-L baseband coding 10.9MHz BW VSAT antenna size 4.5m
HRIT/EMWIN 1694.1MHz L Band Vertical Polarization with offset	BPSK @ 927Ksps/400Kbps ??dBmi at Sat edge footprint Convolution/RS coding SRRC filter alpha=0.3 BW=0.927*1.3=1.205MHz VSAT antenna size 1m

Table 2 GOES16(R) Signal Parameters (Ref.5)

Table 1 is a brief summary of geostationary weather satellites now in orbit according to Ref.3. In this post we will focus on GOES16(R) since it covers a good portion of the Western Hemisphere and is very well documented. Figure 1 shows the GOES16(R) footprint.

GOES16 Propagation Path

Fig.2 Propagation Diagram Observer Same Longitude as Geo Satellite

Figure 2 shows the propagation geometry for an observer located on the same longitude as a geostationary satellite. Distance dcgeo is the distance from the centre of the earth to the satellite located above the equator. Distance dogeo is the propagation distance between the observer and the satellite and Hc is the elevation angle and Lfs is the free space loss in dB. Sample calculations for Toronto, Canada:

Observer Latitude = 43.71degN Longitude = 79.40degW
dogeo = 37816Km Hc = 39.6deg
Lfs = 32.44 + 20*log10(1694.1_MHz) + 20*log10(37816_KM) = 189dB

Fig.3 Propagation Drawing Observer Different Longitude than GeoSatellite

Figure 3 shows the propagation geometry where the observer is on a different longitude than the geostationary satellite. Figure 4 shows the ScicosLab solution for Toronto, Canada to GOES16(R) at 75.2degW. Satellite EIRP of 60dBmi (?? same as DRB) for an HRIT signal. Sample calculations for Toronto, Canada:

Observer Latitude = 43.71degN Longitude = 79.40degW
dogeo = 37830Km Hc = 39.4deg Bearing = 174deg
Rx LNA gain = Gramp =30dB
Rx Ant gain = Grant = 15dB
Grx = Gramp + Grant = 45dB
Lfs = 32.44 + 20*log10(1694.1_MHz) + 20*log10(37830_KM) = 189dB
Pr = Pt + Gt + Gr -Lt – Lr – Lfs = 60dBm + 45 -189 = -84dBm
Pn = Fa + 10*log(BW_Hz) – 174 dBm = 3 + 10*log(1,205,000) – 174 = -110dBm
SNR = 26dB

Fig.5 Rx Location to CN Tower Toronto Canada

Figure 5 shows the azimuth from the Rx location to the CN tower which is 171deg, Figure 6 shows the lucky view from the Rx location showing the CN tower in the middle and about 5deg clearance to both East and West.

Reception Preparation

In order to receive the GOES16(R) signal, rather than piecing components together, I purchased a kit of components from NooElec that was specifically designed for that purpose. Lucas Teske in Brazil (Ref.6) has an excellent video that goes into great detail on how to assemble the package and acquire a signal. Before assembling the antenna, I did some preliminary tests using a Signal Hound spectrum analyzer with/without the SAW+LNA module using a simple vertical that was supplied with my original RTL. Figure 7 shows the spectrum around 1.694GHz without the SAW/LNA module and Figure 8 shows the spectrum with the module. Note the gain and approx. 80MHz bandwidth.