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Deep Space Ground Station - SARCNET

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Deep Space Ground Station
(This page is currently under construction)

This DIY project is a Deep Space Ground Station for receiving signals from selected spacecraft in our solar system. You can receive the signals using a parabolic dish antenna and a Software Defined Radio (SDR), demodulate and display the signals using free software on a Windows PC. Although you can't actually decode the voice, telemetry and science data in the signals, because it is encrypted, just tracking the spacecraft and receiving the signals here on Earth is a real way of being part of the space program. This system works with our SARCTRAC Mk5 antenna rotator. Use our free SARCTRAC Space software software to track the spacecraft, tune your SDR and learn all about the space program by reading the information in the database and following the links to the relevant agency's website.
Table of Contents
Design
Spacecraft transmit signals (voice, telemetry and science data) in various frequency bands as follows:

  • S-Band (2–4 GHz)
  • X-Band (8–12 GHz)
  • Ka-Band (26.5–40 GHz)

To get started with receiving signals from spacecraft, an S-Band setup is the easiest and cheapest. It is typically used for spacecraft near the Earth (for example stationed at the Earth-Sun LaGrange points 1 and 2, up to 1.5 million km away) or in cislunar space (between the Earth and the moon: 225 to 405 thousand km away). However, we will not be able to receive signals from all of these spacecraft due to the technical limitations of the selected components. See Components for further details.
Spacecraft
The following, as best we can tell, is a list of the spacecraft that use the S-Band, their frequency and their antenna polarization (Left- or Right- Handed Circular Polarization) together with their compatibility with the available Patch Feed (2150 - 2350 MHz, RHCP) and Cavity Filter (2170-2300 MHz) used below. The spacecraft locations are shown as: Low Earth Orbit (LEO), High Earth Orbit (HEO), Earth to Moon (CISLUNAR), Moon orbit (MOON), Earth-Sun Lagrange Point 1 (E-S L1), Earth-Sun Lagrange Point 2 (E-S L2). The ones shown in green appear to be the only ones compatible with our system.
Frequency
Polarization
Location
Spacecraft
Patch Feed
Cavity Filter
2203.201140
L
MOON
CHANDRAYAAN-3P (ORBITER)
No
Yes
2214.992781
L
E-S L1
DSCOVR
No
Yes
2216.500000
R
CISLUNAR
ARTEMIS
Yes
Yes
2217.000000
L
MOON
CHANDRAYAAN-2 (ORBITER)
No
Yes
2222.600000
L
HEO
XMM-NEWTON
No
Yes
2241.599800
L
MOON
CHANDRAYAAN-2 (LANDER)
No
Yes
2244.534000
R
E-S L1
SOHO
Yes
Yes
2250.000000
R
HEO
CHANDRA OBSERVATORY
Yes
Yes
2270.408568
R
E-S L2
JAMES WEBB SPACE TELESCOPE
Yes
Yes
2271.200000
R
MOON
LRO
Yes
Yes
2272.000000
R
HEO
TESS
Yes
Yes
2275.000000
R
E-S L1
WIND
Yes
Yes
2278.365682
R
E-S L1
ACE
Yes
Yes
2282.500000
L
MOON
THEMIS-B
No
Yes
2282.500000
L
MOON
THEMIS-C
No
Yes
2482.710675
L
LEO
HUBBLE SPACE TELESCOPE
No
No
Lagrange Points
The table above also emphasises that even in the vacuum of space, in our own solar system, there is some premium real-estate: Special places where the conditions are just right for spacecraft to live. For any two-body system, such as the Sun and the Earth, "Lagrange points" are positions in space where the combined gravitational pull of the two bodies precisely balances the centripetal force needed for a small object (like a spacecraft) to orbit along with them. There are actually five Lagrange points. They each act as "parking spots" allowing spacecraft to stay in a fixed position relative to the two bodies, using a minimal amount of fuel for station-keeping. The five Lagrange points for the Earth-Sun system are shown in the following diagram, which is of course not to scale. They are named after the Italian-born mathematician Joseph-Louis Lagrange.

Sun-Earth Lagrange Points
Polarization
We know by observing static electricity picking up small objects and by playing with small permanent magnets that electric fields and magnetic fields exist and that they can exert a force across a distance of space. We know by observing a moving magnet inducing an electric current in a coil of wire or, conversely, an electric current energising an electromagnet that electricity and magnetism are somehow interconnected. It does not stretch the imagination very much to understand that alternating electric and magnetic fields can also travel through space. However, it is interesting to visualize just how radio waves travel (or propagate). Consider that an electric field (from a battery) across a piece of wire causes an electric current to flow along the wire. If you bring a magnetic compass near the wire you will see the effect of the magnetic field on the compass. The interesting thing is that the direction of the magnetic field is at right-angles to the wire, not along it (try it yourself!). Applying this knowledge to electromagnetic waves, we see that they consist of alternating electric and magnetic fields, always at right-angles to each other, traveling outwards from their origin. To categorize the orientation of the electric field we use the word polarization. If the electric field oscillates in a vertical plane, as shown in the following diagram, we call this vertical linear polarization. If the electric field oscillates in a horizontal plane, we call this horizontal linear polarization. In the following diagram, the electric field is shown in blue and the magnetic field is shown in green.

Vertical Linear Polarization of an Electromagnetic Wave

However, the polarization of the electromagnetic waves is not always linear. The electric and magnetic fields can rotate together around in a circle. We call this circular polarization. If the electric field is constant in magnitude, but rotates anticlockwise (when looking from behind, in the direction of its propagation) we call this Right Hand Circular Polarization (RHCP). If it rotates the other way we call it Left Hand Circular Polarization (LHCP). The diagram below shows a graphical representation of an RHCP electromagnetic wave travelling from left to right. In the following diagram, the electric field is shown in blue and the magnetic field is shown in green. Note: The orange circles help you see the circular motion in the 2D image:

Right Hand Circular Polarization of an Electromagnetic Wave

The above diagram shows both the electric and magnetic fields, but it is still difficult to visualize how the circular polarized waveform propagates. The following animated GIF image of the electric field of a RHCP waveform shows the constant-amplitude, electric field rotating in a counter-clockwise direction (when viewed from behind in the direction of propagation) and the waveform propagating forwards with a right-hand screw format.

Animated GIF Image of the electric field of a RHCP waveform (See: Wikipedia)

In order to transmit and receive radio waves you should always use the same polarization at the transmitter and at the receiver. Circular polarization is not affected by spacecraft rotation about the propagation axis, whereas linear polarization is. For this reason, spacecraft mostly use RHCP (but occasionally LHCP). There will undoubtedly be additional attenuation of the signal if you don't use the same polarization as the spacecraft.
Reflection
When a radio wave hits a conductive surface it can be reflected from that surface. A perfectly conductive surface may reflect almost all of the energy of the incident wave. The rule for the direction of the reflected wave is: "The angle of reflection is equal to the angle of incidence". So, for example, if a wave hits a flat conductive surface at an angle of 30 degrees to the surface it will be reflected in the forward direction and in the same plane at the same angle of 30 degrees from the surface. A parabolic reflector has the additional utility of reflecting all parallel rays hitting the reflector to a single point called the focus.


However, while a reflecting element in an antenna system can be extremely useful in increasing the directivity and hence the gain of the antenna, it also has a very important side effect: The polarization of radio signals hitting the reflector will be inverted: Horizontal linear polarization becomes vertical linear polarization and vice-versa; Right-hand circular polarization becomes left-hand circular polarization and vice-versa. Therefore: To receive RHCP signals from a spacecraft, using an antenna with a parabolic dish reflector, we must use an LHCP (patch or helical) feed at the focus.
Link Budget
A link budget calculation is performed to see if it will be possible to receive a radio signal from a distant spacecraft. It typically includes a calculation of the following quantities:

  1. Spacecraft Transmitted Signal Power
  2. Free Space Path Loss
  3. Ground Station Antenna (F/D Ratio, Efficiency, Effective Area and Gain)
  4. Ground Station Noise Figure
  5. Ground Station System Noise Temperature
  6. Ground Station Figure of Merit
  7. Received Signal Power
  8. Received Noise Power
  9. Received Signal to Noise Ratio
  10. Received Signal plus Noise to Noise Ratio
  11. Artemis II S-Band Downlink Signal Analysis
  12. Link Budget Calculations
  13. Link Budget Conclusions
Decibels
Power levels and power ratios are often measured in decibels (dB). The use of decibels helps compress the huge range of values into manageable floating point numbers, averting the need for scientific (exponential) notation. Decibels are normally relative values, but they can be referenced to useful quantities to indicate absolute values. Another advantage of using decibel values over linear values is that because they are logarithmic they can be added and subtracted instead of being multiplied and divided. Here is a definition of some of the decibel units used herein:

  1. dB: A relative logarithmic unit. An increase in 10 dB in power for example signifies an increase of 10 times the power. So, 20 dB is 100 times the power and 30 dB is 1000 times the power, and so on.
  2. dBm: An absolute logarithmic unit of power level, relative to 1 milliwatt (mW). So 30 dBm = 1 Watt.
  3. dBW: An absolute logarithmic unit of power level, relative to 1 watt (W).
  4. dBi: A relative logarithmic unit of the antenna gain over a theoretical isotropic antenna (which would radiate the same in all directions).
Spacecraft Transmitted Signal Power
The downlink signal from the spacecraft is generated by an on-board transmitter connected to an external antenna. The link budget calculations would be very simple if we knew the output power of the spacecraft transmitter, in dBm, and the gain of the spacecraft antenna, in dBi. Unfortunately, NASA does not publish this information. Instead we have to reverse-engineer this value from observations made by radio telescopes, here on Earth (see later). Since we will never know the actual spacecraft transmitter power and antenna gain, we just represent the spacecraft transmitted power as:

Pt = Spacecraft Equivalent Isotropic Radiated Power (EIRP) in Watts

Where:
Isotropic means the same in all directions
Free Space Path Loss
Imagine a spacecraft and a ground station equipped with (theoretical) isotropic antennas that radiate and receive with unity gain in all directions! Note: We like using isotropic antennas because they provide answers that are independent of antenna gain, which we can always add on later. The transmitted signal expands uniformly in all directions and Equivalent Isotropic Radiated Power (Pt) is spread across the surface of an expanding sphere with a total area of:

As = 4·pi·r2

Where:
As = The spherical area in m2

The power density of that signal is:

Ps = Pt/As

Where:
Pt = The power transmitted (EIRP) in W
Ps = The signal power density in W/m2
As = The spherical area of the signal in m2

The power received by an isotropic antenna is:

Pr = Ps·Ae

Where:
Pr = The received power in W
Ps = The power density in W/m2
Ae = The effective area of any isotropic antenna in m2, which can be shown (not by us) to be: λ2/4·pi
λ = The wavelength of the signal in m

The Free Space Path Loss is the ratio of the power received to the power transmitted:

FSPL = Pr/Pt
FSPL = Ps·Ae/Pt
FSPL = (Pt/As)·Ae/Pt
FSPL = Ae/As, Note it is independent of Pr and Pt
FSPL = (λ2/4·pi)/(4·pi·r2)

FSPL = λ2/(4·pi·r)2

Where:
λ = The wavelength of the signal
r = The range from the transmitter to the receiver
Ground Station Antenna (F/D Ratio, Efficiency, Effective Area and Gain)
The ground station antenna is a major source of signal gain in the link budget. It uses a parabolic, dish-shaped reflecting surface to focus the weak signal from a distant spacecraft onto a small feed antenna, located at its focal point. The focal point of the antenna is either located on the axis of the dish (Prime Focus) or is offset to one side of the dish (Offset Focus).
Ground Station Antenna F/D Ratio
The Focal length to Diameter ratio (F/D ratio) is the single most important parameter characterizing a parabolic dish antenna. It determines the shape, depth, and focal point of the parabolic reflector, fundamentally dictating how the antenna collects and focuses the signal.

The shape of the parabolic dish is characterised by its F/D ratio:

  • Deep Dishes (Low F/D, e.g., 0.25 to 0.35):
    • Shape: Deeper with a focal point located deep inside the dish.
    • Pros: Highly resistant to outside interference and noise from the sides; mechanically rigid.
    • Cons: More difficult to illuminate evenly (the feed antenna requires a wide beamwidth), making them trickier to align perfectly.
  • Shallow Dishes (High F/D, e.g., 0.4 to 0.5+):
    • Shape: Flatter with a focal point suspended further out in front of the dish.
    • Pros: Easier to illuminate evenly with a standard feed antenna; offers a wider field of view for tracking moving objects.
    • Cons: More susceptible to picking up unwanted background noise from around the edges of the dish.
Ground Station Antenna Efficiency
The efficiency of a parabolic dish antenna is determined by many factors. The main ones for our Prime-Focus antenna are:

The polar (radiation) pattern of the feed antenna Pn(θ): This is the gain of the feed antenna, measured at incremental angles (theta) from the axis (or bore-sight) of the parabolic reflector. Since the radiation pattern is symmetrical, only half of the pattern is required: From 0 to 180 degrees or from 0 to pi radians. Similarly only half the range is required for any integration of antenna power ratios.
Polar Radiation Pattern of the G3RUH Patch Feed

One half of the polar radiation pattern (since it is symmetrical) is manually translated into an array of values measured in decibels, at 5-degree increments, as follows:

PndB=[0,0,0,-0.5,-1,-1.5,-2,-2.5,-3,-3.5,-5,-7,-9,-11,-13,-15,-17,-18,-20,-23,-26,-30,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100]

The angle (ψ0): This is the half-angle subtended by the rim to the centre of the parabolic dish antenna at the focal point. Given the F/D ratio:

Illumination efficiency (ηill): The feed antenna may not capture (or fully illuminate) signals over the entire surface of the dish.

Spill-over efficiency (ηspill): The feed antenna may over-capture (or spill-over) signals beyond the surface of the dish

Blockage efficiency (ηblock): The feed antenna partly blocks signals to or from the surface of the dish.

The angle (θb): This is the half-angle subtended by the rim of the shaded area and the centre of the parabolic dish antenna at the focal point. Given d1 = Diameter of the dish and d2 = Diameter of the Feed Antenna:
 



Unlike spill-over efficiency, which is a power ratio, the blockage efficiency uses amplitudes that must be squared to return to a power ratio.

Surface efficiency (ηsurf): The surface efficiency of a mesh dish is limited by two main factors: Surface tolerance (deviation from the ideal paraboloid) called: ηRuze and Mesh porosity (signal leakage) called: ηmesh.
where ε is the RMS surface error ≈ 1.8 mm
where a is the hole size ≈ 3 mm and r is the wire mesh radius (thickness / 2) ≈ 0.2 mm

ηsurf = ηRuze · ηmesh

The overall efficiency of the parabolic dish antenna can be estimated as the product of these individual efficiencies:

η ≈ ηill · ηspill · ηblock · ηsurf
Ground Station Antenna Effective Area
The physical area of a parabolic dish antenna is defined as the cross-sectional area of the widest part of the dish and is derived from the overall diameter of the dish. The effective area of a parabolic dish antenna is the physical area times the antenna efficiency.

A = η·pi·(d/2)2

Where:
A = The effective area of the dish in m2
η = The antenna efficiency
d = The dish diameter in m
Ground Station Antenna Gain
The gain of a parabolic dish antenna is proportional to the effective Area and inversely proportional to the square of the operating wavelength:

G = 4·pi·A/λ2

Where:
A = The effective area of the dish in m2
λ = The operating wavelength in m
Ground Station Noise Figure
Noise Figure (NF) is a measure of the degradation of the signal-to-noise ratio (SNR) caused by components in the receiver. The noise figure of such a component can be expressed as:

NF = 10log₁₀(SNRin/SNRout)

Where:
SNRin= The Signal to Noise Ratio at the input of the component
SNRout= The Signal to Noise Ratio at the output of the component
Ground Station System Noise Temperature
Noise is caused by the random thermal motion of electrons in the environment and system components. Because noise is a thermal phenomenon, the noise from each of these sources is actually measured according to its equivalent temperature in Kelvin (K). Kelvin is an absolute quantity of temperature referenced to Absolute Zero, so it does not use a degree (°) qualifier like the Celsius and Fahrenheit scales. It does use the same magnitude as the Celsius (° C) scale, but it is offset, since 0° C = 273.15 K.

As well as the wanted signal from the spacecraft, the antenna receives unwanted noise from the Earth and the Cosmos. The receiver itself also generates unwanted noise. These individual noise temperatures from the antenna and the receiver can then be added together to calculate the total system noise temperature. The antenna noise has two components: Noise from the sky and noise from the ground. Each of these is proportioned by the spillover efficiency of the feed antenna, which determines how much of the signal is reflected into the feed antenna and how much spills over the edge of the dish. We will calculate the spillover efficiency of our dish later.

Tsys = Ta+Tr = (ηspill*Ts)+((1-ηspill)*Tg)+Tr

Where:
Tsys = Total system noise temperature in K
Ta = Noise from the antenna in K
Tr = Noise from the receiver in K
Ts = Noise from the sky in K
Ts = 8 K at 90° elevation to 36 K at 5° elevation from Recommendation ITU-R P.372-14 (08/2019) Radio noise equation (10)
Tg = Noise from the ground in K = T0
ηspill= Feed antenna spillover efficiency = 0.965 (See below)
Noise Temperature of cascaded elements
For cascaded elements in, for example, a receiver chain: The total noise temperature is calculated from Friis' noise equation:

T = T1 + T2/G1 + T3/(G1·G2) + T4/(G1·G2·G3) + ... Friis equation for noise

Where:
Tn = The noise temperature of element n in K
Gn = The linear gain of element n

The Noise Figure of an active element can be used to calculate its noise temperature:

Tn = T0(NFn-1)

Where:
T0 = Standard Reference Temperature = 290 K
Tn = The noise temperature of element n in K
NFn = The linear Noise Figure of element n

The Gain/Loss of a passive element can be used to calculate its noise temperature:

Tn = T0(Ln-1)

Where:
T0 = Standard Reference Temperature = 290 K
Ln = 1/Gn = The loss of element n

The Gain/Loss of an element can be converted simply:

Gn = 1/Ln

Where:
Ln = The loss of element n

Example 1: Calculate the noise temperature of a receiver with cascaded elements: LNA=1, Filter-2 and SDR=3

Tr = T1 + T2/G1 + T3/(G1·G2)

Where:
Gfil = -0.374 dB = 0.92
NFlna = 0.35 dB = 1.08
Glna = 15 dB = 31.6
Tfil = T0·(1/Gfil-1) = 290·((1/0.92)-1) = 26 K
NFsdr = 3.0 dB = 2.00
Tsdr = T0·(NFsdr-1) = 288.6
T0 = 290 K
T1 = LNA Noise Temperature = T0(NFlna-1) = 290(1.10-1) = 24.3K
T2/G1 = Filter Noise Temperature / LNA Gain = 26/31.6 = 0.82 K
T3/(G1·G2) = SDR Noise Temperature/(LNA Gain·Filter Gain) = 288.6/(31.6·0.92) = 9.9 K
Tr = 24.3+0.82+9.9 = 35.1 K

Example 2: Calculate the noise temperature of a receiver with cascaded elements: Filter = 1, LNA=2 and SDR=3

Tr = T1 + T2/G1 + T3/(G1·G2)

Where:
Gfil = -0.374 dB = 0.92
NFlna = 0.35 dB = 1.08
Glna = 15 dB = 31.6
NFsdr = 3.0dB = 2.00
Tsdr = T0·(NFsdr-1) = 288.6
Tfil = T0·(1/Gfil-1) = 290·((1/0.92)-1) = 26 K
T0 = 290 K
T1 = Filter Noise Temperature = 26 K
T2/G1 = LNA Noise Temperature/Filter Gain = T0·(NFlna-1)/Gfil = 290·(1.10-1)/0.92 = 31.52 K
T3/(G1·G2) = SDR Noise Temperature/(Filter Gain·LNA Gain)= 288.6/(0.92·31.6) = 9.9 K
Tr = 26+31.52+9.9 = 67.4 K

So, it is better to put the LNA before the Filter since that configuration has a lower noise temperature!

We can now calculate the system worst-case noise temperature:

Tsys = Ta+Tr = (ηspill*Ts)+((1-ηspill)*Tg)+Tr = (0.965)(36)+((1-0.965 )·290)+35.1 = 34.74+10.15+35.1 = 80.1 K
Ground Station Figure Of Merit (G/T)
The ground station figure of merit is expressed as the ratio of the ground station antenna gain (G) to the ground station system noise temperature (Tsys). Using G/T greatly simplifies the link budget calculations.

G/T = 4·pi/λ2 ·(A/Tsys)

Where:
A = The effective area of the dish in m2
Received Signal Power
The received signal power is the spacecraft transmitted power less the free space path loss.

Pr = Pt·FSPL or Pr = Pt (in dBm) - FSPL (in dB)

Where:
Pt =  spacecraft transmitted power expressed as Equivalent Isotropic Radiated Power
FSPL = Free Space Path Loss
Received Noise Power
Pn = k·Tsys·B

where:
k = Boltzmann's Constant in W/Hz/K
Tsys = The system noise temperature in K
B = The receiver bandwidth in Hz
Received Signal to Noise Ratio
The Signal to Noise Ratio (SNR) is the ratio of the received signal power to the received noise power. It determines if you can ultimately detect and demodulate a distant radio signal in the presence of noise.

SNR = Pr/Pn

Where:
SNR = The received signal to noise ratio
Pr = The received signal power
Pn = The received noise power in the receiver bandwidth
Received Signal plus Noise to Noise Ratio
The Signal + Noise to Noise Ratio (SNNR) is the ratio of the received signal and noise power to the received noise power. This is useful when looking at the signal on the spectrum display. Since the signal and the noise are combined, the ratio of the signal peak power to the noise floor power is the SNNR. It becomes especially significant when the SNR is low.

SNNR = (Pr+Pn)/Pn = (Pr/Pn)+1 = SNR+1

Where:
SNNR = The received Signal + Noise to Noise Ratio
Pr = The received signal power
Pn = The received noise power in the receiver bandwidth

We now have all the equations we need to figure out if we can see a signal from a distant spacecraft on our spectrum display. The SNNR will tell us the difference between the noisy spacecraft signal and our own receiver noise floor. It represents the height of the signal above the noise on the spectrum display.

To recap we have:

Pr = Pt·FPSL·G
Pn = k·Tsys·B
SNNR = (Pr/Pn)+1
SNNR = (Pt·FPSL·G)/(k·Tsys·B)+1

SNNR = (Pt·FPSL·(G/Tsys)/(k·B))+1

Alternatively, if we know the SNNR, we can re-arrange this equation to calculate the transmitter EIRP:

Pt = (SNNR-1)·k·B/(FSPL·(G/Tsys))

Where:
SNNR = The linear (not logarithmic) difference between the signal peak power and the noise floor power. Convert this value to dB and it will indicate the height of the noisy signal from the spacecraft above the noise floor on our spectrum display.
k = Boltzmann's Constant in W/Hz/K
B = The receiver bandwidth in Hz
Pt = The transmitter EIRP in W
FSPL = The linear Free Space Path Loss
G/Tsys =  The linear Gain to Noise Temperature Ratio in /K

However, to discover the transmitter EIRP we will have to do some more digging.
Artemis II S-Band Downlink Signal Analysis
This analysis is designed to determine if we will be able to "see" any signal from Artemis III on the spectrum display of our Deep Space Ground Station receiver.

Ideally we would just lookup the published transmitter power and antenna gain of the Artemis/Orion spacecraft systems in order to determine its transmitted signal power or Equivalent Isotropic Radiated Power (EIRP). Then use our link budget calulations to determine the SNNR. We actually found the part numbers of some of the avionics here: L3Harris Inside the Avionics That Make Artemis II Possible. From this we discovered that the C/TT-520 S Band Multimode Transponder is the only on-board device with an S-band Transmitter. Its RF Output Power is 5-20 W. However, we struggled finding any information on the antennas. NASA had published a spacecraft components list, which only said that: "Orion uses a high-speed communications system, employing four phased array antennas on the crew module and two phased array antennas on the service module. Phased array antennas allow signals to be controlled and directed without requiring any physical movement of the antenna." In any case, we would require a block-diagram of how these on-board systems were connected and how they were actually used.  

The other approach was to reverse-engineer the data we needed from sources closer to home. Estimating the spacecraft EIRP, in the absence of any published specifications, requires input from a variety of authoritative sources. We needed to analyse the received spectrum display of the Artemis/Orion spacecraft as recorded by participating ground stations on previous flights. From these, we needed to identify operational factors such as signal formats and power level changes; we needed the published specifications of the receiving ground station; we needed to know the modulation characteristics of the transmitted signal and we needed to develop the necessary equations for the spacecraft EIRP. It should be noted that we cannot rely on the displayed absolute power levels of the signal or the noise floor on a spectrum display. This is because we do not know the receiving system gain (particularly from the LNA). We can however rely on the displayed SNNR level, which is the difference between the carrier/PSK peaks and the noise floor, as this is not affected by the LNA gain.  

It should be noted that the signal strength received from the spacecraft is by no means constant and it is a fact that the transmitter output power is controlled in real-time by NASA. Never-the-less, we assumed that if we did enough observations of the strongest received signals and reverse-engineered the EIRP we would get a good approximation. In the end, though, we realised that it was sufficient to compare SNNR readings from other deep space ground systems, and ours, just by subtracting the difference in our respective figures of merit (G/Tsys).  

Information sources:
  1. AMSAT-DL 20m radio telescope at Bochum in Germany:
    1. Live Spectrum Display: https://www.youtube.com/amsatdl/live
    2. Ground station specifications: https://amsat-dl.org/en/20-meter-antenna/
  2. Artemis II 2 GHz Telemetry Downlink modulation characteristics: https://destevez.net/2022/11/decoding-the-artemis-i-orion-vehicle/
  3. Help with Link Budget calculations and verification:
    1. James Miller G3RUH http://www.jrmiller.online/
    2. Felix Rzezniczak VK3FAR https://www.qrz.com/db/VK3FAR

Operational Analysis:
We reviewed the following published YouTube recordings made for each pass of the spacecraft over Bochum in Germany for the Artemis Mission Elapsed Time (MET) as shown:
A typical operational analysis for MET Day 3 looked like this:
  1. https://youtu.be/aF1BmksB6lM?t=2142 Prior to AOS. FFT Max = -70, FFT Min = -102, Noise floor = -95 dB.
  2. https://youtu.be/aF1BmksB6lM?t=2377 Just after AOS for PSK: FFT Max = -70, FFT Min = -102, Noise floor = -95 dB, Carrier+Noise = -73 dB. PSK Peak = -95 dB (on the Noise Floor), Carrier+Noise to PSK Peak Level = 22 dB.
  3. https://youtu.be/aF1BmksB6lM?t=5173 FFT Max decreased to -73.
  4. https://youtu.be/aF1BmksB6lM?t=5629 FFT Max decreased to -75.
  5. https://youtu.be/aF1BmksB6lM?t=6752 Just prior to transition from PSK to OQPSK: PSK Peak Level = - 87 dB, PSK Null Level = -98 dB (3 dB under the Noise Floor!), PSK Carrier+Noise = Off Screen.
  6. https://youtu.be/aF1BmksB6lM?t=6810 Transition from PSK to OQPSK. Note: Carrier disappears.
  7. https://youtu.be/aF1BmksB6lM?t=6841 Just after transition from PSK to OQPSK: OQPSK Peak Level = -80 dB (7 dB above PSK Peak Level), OQPSK Null Level = -98 dB (3 dB under the Noise Floor! Same as PSK).
  8. https://youtu.be/aF1BmksB6lM?t=6950 6 dB power down event. OQPSK Peak Level = -80 dB to -86 dB.
  9. https://youtu.be/aF1BmksB6lM?t=8587 6 dB power up event. OQPSK Peak Level = -88 dB to -82 dB.
  10. https://youtu.be/aF1BmksB6lM?t=21571 Transition from OQPSK to PSK.
  11. https://youtu.be/aF1BmksB6lM?t=24739 Just prior to LOS: PSK Carrier+Noise = -77 dB. PSK Peak = -95 dB (on the Noise Floor), PSK Carrier+Noise to PSK Peak Level = 18 dB. C.F. 2 above.

Artemis II Downlink Signal Formats:
We identified two distinct signal formats used by Artemis II as confirmed by Daniel Estevez above:
  1. OQPSK: Offset Quadrature Phase Shift Keying: Identified by its fully suppressed carrier signal. Just looks like a bump in the noise floor.
  2. PSK: Phase Shift Keying. Identified by its reduced carrier signal. The carrier would be easy to spot on a spectrum display.
Artemis II OQPSK Signal Analysis
1. Spectrum Display:
We searched all the videos above looking for a nice, strong spectrum of the Artemis II OQPSK downlink signal from the AMSAT-DL radio telescope and we found this one at https://youtu.be/KuxABMi7qYk?t=6401 on MET Day 8:

Display from the AMSAT-DL Radio Telescope at the Bochum Observatory

This image is a snapshot of the Artemis II (Orion) downlink being received by AMSAT-DL on their 20m dish at Bochum in Germany. From this image we get so much really useful information:

  1. Date and time: This snapshot was taken on MET Day 8 of the Artemis II mission on its return to Earth.
  2. Centre Frequency = 2.2165 GHz
  3. Actual Frequency = 2.216509018 GHz
  4. Antenna polarization: Right-Hand Circular Polarization
  5. Range = 184034 km
  6. Range-Rate = -1542000 m/s
  7. Received signal peak power: Ps = -80 dB
  8. Received noise floor power: Pn = -95 dB. Note that the OQPSK Nulls show on the display at -98 dB are actually 3 dB below the noise floor!
  9. Received SNNR = (-80) - (-95) = 15 dB
  10. Sample Rate = 8 Msps
  11. Decimation = 1
  12. Bandwidth: B = 8 MHz (Sample Rate / Decimation)
  13. FFT Size = 131072 bins
  14. FFT Rate = 50
  15. Avg Num = 150
  16. Spectrum display Resolution Band Width:  RBW = 8 MHz/131072 = 61 Hz: The width of each frequency bin.
  17. OQPSK has a fully suppressed carrier
  18. OQPSK "null-to-null" bandwidth = 4 MHz or 6 MHz giving the OQPSK Sample Rate = 2 Msps or 4 Msps.

2. AMSAT-DL published specifications:
G/Tsys: 30 dB @ 2.3GHz, 32.6 dB @ 2.4GHz.
We extrapolated this to get G/Tsys @ 2.2165GHz = 30.0 - (2.3 - 2.2165)·(32.6 - 30.0)/(2.4 - 2.3) = 27.8 dB

3. Estimation of the Artemis II OQPSK S-Band Transmitter EIRP:

Pt = (SNNR-1)·k·B/(FSPL·(G/Tsys))

Where:

SNNR = 15 dB
k = 1.38e-23 W/Hz/K
B = 2 MHz (Note: We are using the OQPSK symbol rate here and not the receiver bandwidth*)
FSPL at 184034 km = 204.7 dB
G/Tsys = 27.8 dB/K

Converting all these to their linear equivalents we get:

Pt =  407 W EIRP

5. Calculation of the Deep Space Ground Station Received SNNR for the OQPSK S-Band downlink for Artemis II at the Moon:

SNNR = (Pt·FPSL·(G/Tsys)/(k·B))+1

Where:
Pt = 407 W EIRP
k = 1.38e-23 W/Hz/K
B = 2 MHz (Note: We are using the OQPSK symbol rate here and not the receiver bandwidth*)
FSPL at 405696 km = 211.5 dB
G/Tsys = 27.8 dB/K

Converting these values to their linear equivalents we get:

SNNR = 0.65 dB for the Artemis II OQPSK signal at the Moon
Artemis II PSK Signal Analysis
We searched all the videos above looking for a nice spectrum of the Artemis II PSK downlink signal from the AMSAT-DL radio telescope and we found these ones at https://youtu.be/qxc7PgyvhMU?t=698 and https://youtu.be/qxc7PgyvhMU?t=3844 on MET Day 7. We had to take two screenshots since the full height of the carrier and the PSK signal is not visible in the same frame. We had to add the carrier-PSK height to the PSK-noise floor height to get the full picture of the carrier plus the PSK waveform.

1. Spectrum Display:

The Artemis II PSK downlink showing the full height of the carrier 15 dB above the PSK waveform (just starting to be visible on the noise floor)

The Artemis II PSK downlink showing the full height of the PSK waveform 12 dB above the noise floor

This image is a snapshot of the Artemis II (Orion) downlink being received by AMSAT-DL on their 20m dish at Bochum in Germany. It should be noted that the signal strength received from the spacecraft is by no means constant. To estimate the EIRP we used the strongest PSK signal we could find.

  1. Range = 297564 km
  2. FSPL at 297564 km =

2. AMSAT-DL Radio Telescope published specifications:
G/Tsys = 27.8 dB/K

3. Artemis II S-Band PSK Telemetry Downlink Transmitter EIRP estimation:

Pt = (SNNR-1)·k·B/(FSPL·(G/Tsys))

Where:

SNNR = Carrier level above the noise floor = 15 + 12 = 27 dB
k = 1.38e-23 W/Hz/K
B = 2 MHz (Note: We are using the OQPSK symbol rate here and not the receiver bandwidth*)
FSPL at 297564 km =
G/Tsys = 27.8 dB/K

Converting these values to their linear equivalents we get:

Pt =

4. Calculation of the Deep Space Ground Station Received SNNR for the PSK S-Band downlink for Artemis II at the Moon:

SNNR = (Pt·FPSL·(G/Tsys)/(k·B))+1

Where:
Pt = W EIRP
k = 1.38e-23 W/Hz/K
B = 2 MHz (Note: Using the OQPSK symbol rate here and not the receiver bandwidth*)
FSPL at 405696 km = 211.5 dB
G/Tsys = 27.8 dB/K

Converting all these to their linear equivalents we get:

SNNR = dB for the Artemis II OQPSK signal at the Moon
Link Budget Calculations
Here are our link budget calculations for Artemis III. The Python script for it can be found here. First, a note on the terms we used because they are not strictly correct: Our Signal to Noise Ratio (SNR) is the same as Carrier to Noise Ratio (CNR), our Signal plus Noise to Noise Ratio (SNNR) is the same as the Energy per symbol to noise power density (Es+N0)/N0. We chose these terms because we didn't want to explain what energy per symbol means and it simplifies our understanding.

Click here to see our Link Budget calculations
Link Budget Conclusions
Our link budget calculations indicate that we will only just be able to display the OQPSK signal from the future Artemis III spacecraft, in the vicinity of the Moon, transmitting a whopping 32 dBW signal, using a small 1.8 m satellite TV dish connected to a S-band receiver with a noise figure of 0.35 dB. Our G/T of 10 dB/K is pretty small.

Unfortunately this rules out using this system to receive any of our targeted spacecraft stationed at Earth-Sun Lagrange points, 150 million km away. It is even doubtful we would be able to see the Lunar Reconnaissance Orbiter (LRO), which according to two sources has an EIRP of between 26 and 29 dBW.

We can of course narrow the bandwidth of our receiver to reduce the noise. That will be our strategy for seeing reduced-carrier PSK signals, but these calculations relate to seeing the 4MHz wide, suppressed-carrier, OQSPK signals.

As disappointing as this conclusion may be, it is certainly not unexpected: The professional NASA Deep Space Network (DSN) uses 70 m, 34 m and 26 m dish antennas. As in most cases: Everything is designed for a purpose. In space communications, where spacecraft power and antennas are small, the link budget is very tight, indeed.
Setup
The Deep Space Ground Station setup is as follows:

Deep Space Ground Station Setup

  1. The parabolic dish needs to be large enough to have sufficient gain to receive weak signals from space. It needs to be securely mounted on a heavy-duty, azimuth-elevation rotator capable of steering the dish to any point in the sky, under computer control, of course. We will use our SARCTRAC Mk5 rotator and our SARCTRAC Space software running on a Windows PC. The rotator will be controlled over the 5 GHz home WiFi network so as not to interfere with the 2.2 GHz spacecraft signals.
  2. The Patch Feed needs to cover the spacecraft downlink frequency range and also be LHCP to receive RHCP signals when used with a parabolic reflector. It needs to fully illuminate (cover) the parabolic reflector area given the F/D ratio of the dish.
  3. The Low Noise Amplifier (LNA) needs to amplify signals in the spacecraft downlink frequency range. It should have a low Noise Figure and a high gain.
  4. The Band-Pass Filter (BPF) needs to pass the spacecraft downlink frequency range and block all other interfering frequencies. It needs a sharp cut-off at frequencies above and below the pass-band (operating) frequency. It is particularly important in stopping strong out-of-band signals from entering the SDR.
  5. The Software Defined Radio (SDR) needs to tune, filter and quadrature-demodulate (producing in-phase, I, and quadrature phase, Q, signals) a chunk of the radio spectrum containing the spacecraft signals, then digitize it and send it as a digital data stream to the SDR software running on a PC. Since we are not using a downconverter, the SDR must directly tune the spacecraft downlink frequency. It must have a very stable local oscillator so that the tuning does not drift in frequency, with temperature changes. The PlutoSDR gets hot and needs a cooling fan.
  6. The WiFi router needs to send the wide-bandwidth, digital, data stream from the SDR to the PC over the home HiFi network using the 5 GHz band so as not to interfere with the 2.2 GHz spacecraft signal.
  7. The DC/DC Converter needs to accept 24 VDC and efficiently convert it to 5 VDC to power the LNA, SDR and WiFi router.
  8. To reduce coaxial cable losses between the devices we will try to put the patch feed and all the electronics at the focus point of the parabolic dish in a cowling made from 120 mm round, PVC tubing, with a flat end cap.

Test Bench Setup with Cooling Fan and Power Pack added

Parabolic Dish
The parabolic dish is used as the reflector component in a parabolic antenna. It functions similarly to the reflector in a flashlight: It focuses the radio waves into a narrow beam. Instead of a light globe in a flashlight, a smaller "feed" antenna is placed at the focus of the parabolic dish. The main advantage of a parabolic antenna is that it increases the strength of the received signals due to its high directionality. In radio and electronics: "increasing the strength" is called "gain" and it is measured in decibels (dB). Parabolic dishes can have a solid, mesh or grid type of metal reflector. The focal point can be along the axis (prime focus) or off-axis (offset feed). We expect that a solid, prime focus dish would be the best, but you have compare the specifications for operating frequency, gain and F/D ratio as well as the cost and local availability.

The F/D ratio (focal length-to-diameter ratio) in a microwave dish is a key geometric parameter that defines the curvature and depth of the parabola, crucial for matching the dish with the correct feed antenna.

  • Focul Length (F) represents the distance from the centre of the dish to the focal point where the feed antenna is placed.
  • Diameter (D) represents the diameter of the dish.

The F/D ratio dictates how the feed antenna must distribute its energy. Low F/D (deep dish): Needs a wide-beam feed antenna to illuminate the entire surface without wasting energy, as the feed is close to the dish centre. High F/D (shallow disk): Requires a narrower-beam feed antenna, as the focus is further away. When procuring a satellite TV parabolic dish for this project the most important thing is to find one in your area that you can pick up, as postage charges can be prohibitive.

SatKing 1.8M C-Band Mesh Dish Heavy Duty
  1. Type: Prime Focus, Mesh
  2. Operating frequency: 1.0-12.75 GHz
  3. Gain 36 dB C-Band
  4. Gain 45 dB Ku-Band
  5. F/D Ratio 0.35
  6. Mesh thickness 0.6 mm
  7. 40 cm base
  8. 4 panels
  9. Can be motorized
  10. 75 mm pole diameter

SatKing 1.8M C-Band Mesh Dish Heavy Duty

Helical Feed
The Helical Feed for a parabolic dish is possibly the simplest and cheapest solution. This small antenna, placed at the focus of the parabolic dish "feeds" off the reflected spacecraft signal. For more information see yhis excellent article for a 60cm S-Band Dish Antenna by James Miller G3RUH.
James Miller G3RUH explains the Helical Feed System for a Parabolic Dish
Patch Feed
We will initially be using a helical feed, however, we know it has limitations as it does not make the best use of the available parabolic dish surface. More importantly, in relation to a parabolic dish and its feed system, the G/T ratio or "Gain-to-Noise-Temperature ratio" is considered the fundamental "figure of merit" for evaluating the performance of a receiving ground station.

  • Gain (G): Relates to the size and efficiency of the dish. Larger dishes generally have higher gain, allowing them to collect more signal.
  • Noise Temperature (T): Quantifies the noise generated by the antenna and the electronics (such as the LNB/receiver).

A high G/T means the antenna provides strong signal amplification relative to the noise it introduces, making it crucial for high-quality satellite communications.

There is an excellent article on this subject by James Miller G3RUH, who explains the problem and provides an elegant solution.


Patch Feed Measured SWR

Patch Feed Measured Data
Patch Feed By James Miller G3RUH
NanoVNA S11 Testing
Low Noise Amplifier
Qorvo's TQP3M9037 is a high linearity, ultra low noise gain E-pHEMT block amplifier in a small 2x2 mm surface-mount package. At 1.9 GHz, the amplifier typically provides 20 dB gain, +35 dBm OIP3, and 0.4 dB noise figure while drawing 65 mA current from a 5V supply.

TQP3M9037-LNA
  1. Power Supply： 5 V, 65 mA，MicroUSB Connector
  2. Frequency：100 kHz - 6 GHz
  3. Noise Figure: 0.4 dB @ 1.9 GHz
  4. Gain：15dB @ 2.22 GHz
  5. Input/Output Impedance: 50 Ohm Nominal
  6. RF Connector: SMA female
  7. Size: 45*45*18.5mm
  8. Weight: 46g

TQP3M9037-LNA Measured Gain

TQP3M9037-LNA Measured Data

TQP3M9037 Low Noise Amplifier

NanoVNA S21 Testing
Band Pass Filter
Strong local signals from cellular networks can cause wideband Software Defined Radios such as the one used here to overload. A band-pass filter is required to stop the interfering signals and pass the wanted signals. It must be selected for the band of interest. Luckily there is one specifically made for this purpose:

Sysmocom S-Band Cavity Filter 2170-2300 MHz (cf2235-kt30 v1)

This is a cavity band-pass filter for the 2170-2300 MHz S-Band. You can use it to attenuate any out-of-band interference while receiving only the wanted band. It will attenuate any transmissions from the nearby 2.1 GHz cellular band by >= 30 dB. Both connectors are SMA (female). There is a datasheet for the filter here.

  1. S-Band Cavity Band-Pass Filter
  2. Pass Band: 2170 - 2300 MHz
  3. Insertion Loss: <= 1.0 dB
  4. Passband Ripple: 0.8 dB
  5. Rejection: 30 dB @ < 2160 MHz
  6. VSWR: <= 1.30
  7. Impedance: 50 Ohms
  8. Power: 30 W average
  9. RF power (max): 30 W
  10. Temperature: -20 to 50 Centigrade
  11. Dimensions: 124x47x33 mm
  12. Weight: 186 g
  13. IP-Rating: IP50

Sysmocom Cavity Filter Measured Gain

Sysmocom Cavity Filter Measured Data
Sysmocom S-Band cavity filter 2170-2300 MHz (cf2235-kt30 v1)

NanoVNA S21 Testing
SDR
The Software Defined Radio is a critical component in the deep space ground system. It tunes, selects and partly demodulates the signal from the spacecraft, returning a wideband, digital data stream that can be fully demodulated, processed and viewed by free PC software. The main feature of the SDR is that it must work at the Ultra High Frequencies (UHF: 300 MHz - 3 GHz) used by spacecraft in order to avoid the need for an expensive additional component called a downconverter or LNB. Next, it must have good frequency stability to keep the signal properly tuned.

Selecting an SDR is a complex tasks with lots of trade-offs. We chose what we think is the cheapest solution that will provide good-enough performance for our project. It is an unenclosed PCB module that will require some heat sinking, possibly even a fan, and housing inside a weather-proof case.

OpenSourceSDRLab 70MHz-6GHz Zynq7020+AD9363 SDR Software Defined Radio Development Board
  1. Dual transmitting and receiving ports.
  2. Supports both USB2.0 and gigabit Ethernet ports.
  3. AD9363 chip with new firmware to support a frequency range of 70MHz~6GHz.
  4. 0.5 ppm (parts per million stability) VCTCXO (Voltage Controlled Temperature Compensated Crystal Oscillator)
  5. Board size: about 5 x 8cm
  6. RAM: DDR, 1GB
  7. Flash: N25Q128 128 Mbit serial flash memory
  8. SDHC card, can be used to start.
  9. Integrated FT2232 debugger, with serial port.
  10. SDR Console supported bandwidths: 576, 768, 960 kHz, 1.536, 1.92, 2.304, 2.688, 3, 4, 4.5, 5, 5.5 and 6 MHz.
  11. SatDump
  12. The actual measured current did not exceed 0.7A peak and 0.52A @ 576 kHz and 0.61A @ 6MHz average
OpenSourceSDRLab 70MHz-6GHz Zynq7020+AD9363 SDR Software Defined Radio Development Board
WiFi Router
The SDR board has an Ethernet port providing the high bandwidth I/Q data required for demodulation by a desktop computer running SDR Receiver software such as SDR Console. Since the feed antenna, LNA and SDR board will be mounted in close proximity to the dish antenna, we need a way to get this data to a PC via our home WiFi network. The wireless connection preferred is 5 GHz, not 2.4 GHz, so as not to interfere with the receiver. We will have to use an AX3000 Gigabit WiFi 6 router to handle the WiFi data rate (We tried an AC750 100 Megabit WiFi 5 router and it wasn't fast enough). We will connect the SDR Receiver Ethernet port to its gigabit Ethernet LAN port. When set to "Client" mode this router will connect the SDR Receiver to our home WiFi network.

TP-Link TL-WR3002x Travel Router
  1. Standards and Protocols: Wi-Fi 6, IEEE 802.11a/n/ac/ax 5 GHz, IEEE 802.11b/g/n/ac/ax 2.4 GHz
  2. WiFi Speeds: AX3000, 5 GHz: 2402 Mbps (802.11ax), 2.4 GHz: 574 Mbps (802.11ax)
  3. Working Modes Router Mode: USB Tethering Mode, 3G/4G USB Modem Mode, Hotspot Mode (WISP Mode), Access Point Mode, Range Extender Mode, Client Mode
  4. Network Security SPI Firewall, Access Control, IP & MAC Binding, Application Layer Gateway
  5. WiFi Encryption: WPA2-PSK, WPA3-Personal, WPA/WPA2-Enterprise
  6. Ethernet Ports: 1 x 2.5 Gigabit WAN Port, 1 x 1 Gigabit LAN Port
  7. USB Support: 1 × USB 3.0 Port
  8. Power: 5 V @ 3 A. The actual measured current did not exceed 0.7A peak and 0.5A average.
  9. Dimensions (W×D×H): 105 × 91.3 × 30 mm
TP-Link WR3002x Wireless Portable Router
DC/DC Converter
To power the LNA, SDR and WiFi router we need a local 5 VDC regulated supply. This XL4015 DC/DC converter module is small and will efficiently step down the 24 VDC supply used for the SARCTRAC Mk5 Rotator. The output will be split into three micro USB cables to feed the devices.

XL4015 DC/DC Converter
  1. Wide 8V to 36V Input Voltage Range
  2. Output Adjustable from 1.25V to 32V
  3. Maximum Duty Cycle 100%
  4. Minimum Drop Out 0.3V
  5. Fixed 180KHz Switching Frequency
  6. 5A Constant Output Current Capability
  7. Internal Optimize Power MOSFET
  8. High efficiency up to 96%
  9. Excellent line and load regulation
  10. Built in thermal shutdown function
  11. Built in current limit function
  12. Built in output short protection function

XL4015 DC/DC Converter
PlutoSDR Setup
The general objectives for the PlutoSDR are as follows:
  • Support a bandwidth of at least 5 MHz at 2.2 GHz to fully capture a spectrum display of the Artemis downlink.
  • Optionally provide sufficient performance for jitter-free reception.
  • Setup using the USB port then utilize the Ethernet port for data.
  • Use a small, 5V, WiFI 6 Travel Router in Client Mode on 5 GHz (away from 2.2 GHz) to provide a Home WiFi interface.
  • Connect to it via WiFi using SDR Console and a Windows PC.

The following procedure was used:
  1. Make a backup of the original micro SDHC card using Win32DIskImager. Requires an 8GB SDHC sard.
  2. Must provide a small cooling fan for the basic PCB, even if heatsinks are provided.
  3. Connect a 5V 2A plugpack, via a micro USB cable, to the DEBUG port to power the device independent of the USB port.
  4. Connect a PC, via a micro USB cable, to the USB port for configuration.
  5. Connect a PC, via a CAT5e Ethernet cable, to the Ethernet port for data.
  6. Connect a VHF/UHF antenna, via an SMA cable, for testing purposes.
  7. Configure the home WiFi Router DHCP server to reserve free space for the following IP addresses:
    1. 192.168.1.4 for the PlutoSDR.
    2. 192.168.1.5 for the Travel Router.
  8. Download and install the PlutoSDR Mk2 USB Windows drivers on the PC from:
  9. Start Device Manager on the PC:

    Device Manager showing new PlutoSDR devices

  10. Note the following new PlutoSDR devices in the Device Manager:
    1. Disk drives: Linux File Stor Gadget USB Device
    2. Network adapters: PlutoSDR USB Ethernet/RNDIS Gadget
    3. Portable Devices: D:\
    4. Ports (COM & LPT): PlutoSDR Serial Console (COM3)
    5. Universal Serial Bus devices: IIO
  11. Explore different views into the PlutoSDR.
  12. First explore the PlutoSDR via the new USB Drive.
    1. Open a File Explorer window.
    2. Open PlutoSDR (D:)
    3. Double-click "info.html" to open a browser.
      1. Observe the Welcome to Analog Devices Active Learning Module-PLUTO web page.
      2. This page provides some useful information about the connected PlutoSDR device.

        Analog Devices Active Learning Module-PLUTO web page

    4. Double-click "config.txt" to open a text editor on your PC. This file shows the current PlutoSDR user configuration:

      # Analog Devices PlutoSDR Rev.C (Z7020-AD9363)
      # Device Configuration File
      # 1. Open with an Editor
      # 2. Edit this file
      # 3. Save this file on the device USB drive
      # 4. Eject the device USB Drive
      # Doc: https://wiki.analog.com/university/tools/pluto/users/customizing

      [NETWORK]
      hostname = pluto
      ipaddr = 192.168.2.1
      ipaddr_host = 192.168.2.10
      netmask = 255.255.255.0

      [WLAN]
      ssid_wlan =
      pwd_wlan =
      ipaddr_wlan =

      [USB_ETHERNET]
      ipaddr_eth = 192.168.1.4
      netmask_eth = 255.255.255.0

      [SYSTEM]
      xo_correction =
      udc_handle_suspend = 0
      # USB Communication Device Class Compatibility Mode [rndis|ncm|ecm]
      usb_ethernet_mode = rndis

    5. Enter the new fixed IP address for the Ethernet port so you can easily find the PlutoSDR on your WiFi network:
    6. Under [USB_ETHERNET] add: ipaddr_eth = 192.168.1.4
    7. Note that ipaddr_eth = <blank> means that Pluto gets the Ethernet port IP address from your DHCP server.
    8. Save the file and eject the PlutoSDR (D:) drive from your PC to write it permanently to the PlutoSDR.
  13. Use PuTTY to open the PlutoSDR Serial Console COM Port
    1. Open PuTTY. Select COM Port 3 Serial 9600bps
    2. Observe the PlutoSDR Serial Console via USB Serial.
    3. Login:
      1. Observe: Welcome to Pluto
      2. pluto login: root
      3. Password: analog
      4. Observe: Welcome to PlutoSDR
    4. Note: The PlutoSDR Serial Console presents a customized embedded Linux operating system, utilizing a Buildroot-based root filesystem and an Analog Devices-maintained Linux kernel.
    5. Type: ifconfig
    6. Observe the previously saved IP settings:

      PlutoSDR Serial Console

  14. Some useful PlutoSDR Serial Console commands are as follows (The first 3 are unnecessary for this version):
    1. Upgrade to AD9364 (Frequency & Bandwidth Extension): fw_setenv compatible ad9364
    2. Revert to AD9363 (Default): fw_setenv compatible ad9363
    3. Enable 2R2T Mode (for Pluto+ hardware): fw_setenv mode 2r2t
    4. Check Current Configuration: fw_printenv
    5. Reset Environment Variables (if needed): fw_setenv attr_name or fw_setenv attr_val
    6. Save & Apply Changes: reboot
    7. Shutdown: poweroff
SatDump Setup
SDR Console Setup
The general objectives for the SDR Console are as follows:
  • Connect to the PlutoSDR via USB or Ethernet
  • Select frequencies up to 2.2 GHz
  • Select bandwidths up to 6 MHz
  • Display the spectrum and waterfall of received signals

The following procedure was used:

SDR Console Cleanup
  1. This is important if a previous version of SDR Console was installed or if SDR Console starts crashing with "Please Wait".
  2. Open a cmd window as administrator and type the following commands using your user Name:
    1. winget uninstall "SDR-Radio.com (SDR Console)"
    2. rmdir /s /q "C:\Program Files\SDR-Radio.com (V3)"
    3. rmdir /s /q "C:\Users\Name\AppData\Roaming\SDR Console"
    4. rmdir /s /q "C:\Users\Name\AppData\Roaming\SDR-RADIO.com (V3)"
    5. reg delete "HKEY_CURRENT_USER\Software\SDR-RADIO.com (V3)" /f

SDR Console Installation
  1. Download and run “SDR-Radio V3.4, 64-bit, 2026-02-11_1214”
  2. Start SDR Console. Select: Definitions | Add
  3. Enter Radio Definitions for the PlutoSDR USB and Ethernet ports matching your config.txt file:

    Radio Definition for PlutoSDR USB Port

    Radio Definition for PlutoSDR Ethernet Port

  4. Select the PlutoSDR USB or PlutoSDR Ethernet definitions to test the installation. Reduce the bandwidth if jitter is a problem.

    Select Radio Definition

  5. Selectable bandwidths for PlutoSDR on SDR Console: 576, 768, 960 kHz, 1.536, 1.92, 2.304, 2.688, 3, 4, 4.5, 5, 5.5, 6 MHz
WiFi Router Setup

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