Introduction
Recently I read an interesting post on an sdr newsgroup discussing the Es’hail 2 satellite also known as QO-100 (Qatar Oscar 100). This is a geostationary satellite designed for DBS or direct broadcast television transmission to North Africa and the Middle East (Ref.1). The satellite has Ku (12-18GHz) and Ka (27-40GHz) band transponders for commercial use and an amateur radio satellite service with 2.4GHz uplink and 10.45GHz downlink. Since I have been recently working with L band satellite reception (GPS, GOES16, H_Line), I decided to investigate possible reception/transmission with this satellite or other similar AMSAT satellites. AMSAT-DL has done considerable work in this area (Ref.2). What makes this unique over other AMSAT satellites, is that it is geostationary. Most amateur radio satellites are LEO Low Earth Orbiting (Ref.3).
QO-100 Parameters
| QO-100 Satellite Parameters |
| General Long = 26degE Elev = 35,794Km (avg) Transponders Commercial= Ku, Ka Transponders Amateur Radio = 2.4GHz (13cm), 10.45GHz (3cm) |
| Uplink Narrow Band: 2400.05 – 2400.30MHz = 250KHz / Pol = RHCP Wide Band: 2401.50 – 2009.50MHz = 8MHz / Pol = RHCP |
| Downlink Narrow Band: 10489.55 – 10489.80MHz = 250KHz / Pol = Ver Wide Band: 10491.00 – 10499.00MHz = 8MHz / Pol = Hor |
Figure 1 shows the location of QO-100 right over the middle of Africa in the Democratic Republic of Congo. Figure 2 shows the footprint elevation contour limits of 10deg & 5deg. For North & South America, only North East Brazil fits into the footprint. Figure 3 shows the Scicoslab routines to calculate dish parameters from my QTH and from Natal Brazil. Unfortunately the satellite is at an azimuth of 79deg and 19deg below my horizon, but from Natal Brazil the azimuth is 87deg and elevation of 21deg.
SDR Receiver Selection
| SDR | Frequency Range |
| SDR-IQ | 500Hz – 30MHz |
| RTL-SDR R820T Tuner | 25 – 1700MHz |
| RTL-SDR E4000 Tuner | 65 – 2300MHz |
| Adalm Pluto | 325 – 3800MHz (duplex operation rx & tx ports) 70 – 6000MHz (freq mod ad9363-ad9364) |
| HackRF1 | 1 – 6000MHz (simplex operation rx/tx port) |
Figure 5 is a table of SDR radios that I presently have. The regular RTL-SDR tops off at 1700MHz, the RTL-SDR with the enhanced E4000 tuner goes up to 2300MHz. Both the HackRF1 and Adalm Pluto can receive up to 6GHz. The Pluto has the advantage that it is full duplex, whereas the HRF1 is only half duplex. So of the above SDRs, the Pluto is a good bet for satellite comms.
PLUTO-SDR Basics/Updating
The Pluto-SDR comes in a small blue box with two stub antennas on both the rx & tx ports as in Figure 6. Since we are dealing with microwave transmission, it is important to know the tx antenna VSWR. I attached the stub antenna to the top port of the NanoVNA and ran the test over 500 – 1500MHz. The antenna has a VSWR of 1.3:1 at 850MHz and is <=2:1 over 830 – 870MHz (Fig.7).
Pluto-SDR is essentially a Linux RaspberryPi controlling a transceiver chip. It is totally flexible and can be accessed via a serial or ethernet connection. I was fortunate to attend an AD seminar with the developers Robin Getz & Travis Collins and a similar seminar is available on line (Ref.4). A very easy way to access the Pluto, is to use Putty on a serial connection over the usb as shown in Figure 8. Login as root/pswd=analog. The AD Pluto Wiki has instructions for getting the extended frequency range of the AD9364. Figure 9 shows the two commands used to see if this variable is set.
Since I purchased the Pluto several years ago, I decided to update the firmware and driver. When you connect the Pluto, it appears as a drive letter PlutoSDR (D). In the drive directory, the “config.txt” file lists the networking parameters. The “info.html” is a getting started help file. It has links on how to update the driver and firmware. You can download the latest driver/firmware from Analog Devices. In Windows device manager, you can then update the driver pointing to the new driver file. For the firmware, just copy the “pluto.frm” to the Pluto SDR (D) directory and eject the device. Once the blue led stops blinking, it will appear as a drive letter again and can be used.
Pluto-SDR with SDRangel
I tested the Pluto at various frequencies to measure the power output. It varied from -6dBm at 70MHz to +3dBm at 433MHz as shown in Figures 11/12/13. I setup the transmitter using SDRangel with an AM channel modulator with m=0% and measured the power on a Signal Hound spectrum analyzer.
SDRangel is an excellent platform for using the Pluto. I setup a transmitter (Fig.14) and receiver (Fig.15) on different work spaces for an uncluttered layout. I looped the tx back to the receiver with an sma jumper cable and 30dB attenuator.
In the next posts we will pursue this further, hopefully being able to access some traffic. I am heading down to the tropics soon, so I may be able to access the footprint.
Please send your comments, questions and suggestions to:
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References
#1. – “Es’hail 2 Satellite”, Wikipedia
https://en.wikipedia.org/wiki/Es%27hail_2
#2. – “AMSAT-DL”
https://amsat-dl.org/en/eshail-2-2/
#3. – “Getting Started with Amateur Satellites”, WA4SXM
https://www.amsat.org/product/2020-edition-of-getting-started-with-amateur-satellites-digital-download/
#4. – “Introduction to the ADALM-Pluto SDR”, Travis Collins & Robin Getz
https://www.youtube.com/watch?v=05nLPVJW9Uo
