Antenna Debug Guide
Although most people will never need to use the antenna debugger, it is still a useful tool to understand why a connection does or doesn't work, and how you can change that.
Once you're feeling confident in your ability to read the Debug menu, try answering some of the example questions!
For this example, we will use the Apollo HGA in lunar orbit to demonstrate how to interpret the Antenna Debug window
When the connection debug window is first opened, it will show a list of all antennas in the same radio band that have a direct line-of-sight to the antenna being debugged, including antennas on other vessels. This means antennas obstructed by the Earth or other planets will not be shown in this window. To continue, choose an antenna to keep debugging. For this example, we will choose DSS 14 - Goldstone.
Once an antenna is selected, the full debug readout for that connection will open.
The first parts shown in the connection debug readout is the Transmitter and Receiver information.
This is the antenna being used on both sides of the connection. Here, we can see the transmitter is the Apollo High Gain Antenna located on the vessel Apollo Test, while the receiver is DSNTrackingStation on Earth
This shows the power output of the transmitter (30 dbm) and the amount of power received by the receiver (-87.84 dbm)
This shows the target the transmitter and receiver are pointing at, and the relative locations of those targets (these locations use game engine coordinates and aren't important to the player). This shows the Apollo High Gain Antenna is pointed at Earth. You may notice the target field for the DSNTrackingStation is blank. This is because tracking stations on earth are considered to be able to point at everything at the same time, so they have no "target".
This shows the position of the transmitter and receiver. These positions are relative using game engine coordinates, like the target position, and aren't important to the player.
This shows the 3 dB-width of the antenna beam in degrees, or how far something needs to be off the centerline of the antenna beam for it to suffer 3 dB of losses. This is also shown in the map view as a dark purple cone, and is inversely proportional to antenna gain. The Apollo High Gain Antenna has a beamwidth of 6.97 degrees, while the much higher gain DSNTrackingStation has a beamwidth of only 0.15 degrees.
This shows the relative pointing of the two antennas at each other. The Apollo High Gain Antenna is pointed at the Earth, not the DSNTrackingStation directly, so it has an Angle-of-Attack of 0.6 degrees, which means the DSNTrackingStation is 0.6 degrees off the center of the antenna beam. This is much smaller than the antenna 3 dB-width of the antenna beam (6.97 degrees), so the losses due to pointing inaccuracies should be minor. The DSNTrackingStation has an Antenna AoA of 0 degrees (since as mentioned above, Tracking Stations are considered to be perfectly pointed at everything) which is smaller than it's 3-dB beamwidth of 0.15 degrees, so it's losses due to pointing inaccuracies should be minor. You will notice the DSNTrackingStation also has an Antenna Elevation reading. This is the degrees of antenna elevation above the horizon of the Earth (such that an antenna will be pointing straight up at an elevation of 90 degrees). Just as the sun appears to warp and change color as it approaches the horizon, radio waves that pass low to the horizon will also be warped and changed, causing atmospheric noise. This effect only becomes significant below about 10 degrees of antenna elevation.
This shows the amount of noise present in the connection. Noise values are measured as a temperature in Kelvin, with the amount of noise a source emits being quantified as how hot it would need to be to radiate that amount of noise power (more information here). The "colder" a noise source, the less noise it adds to a signal.
This is the amount of noise added when the radio signal passes through an atmosphere. As mentioned in Antenna AoA and Antenna Elevation, the lower a tracking station antenna elevation, the more atmospheric noise it experiences, with significant noise added below 10 degrees elevation. In our example, the DSNTrackingStation antenna elevation was 51.8 degrees, much higher than 10 degrees, so the amount of atmosphere noise is very low at only 3K.
This is the amount of noise added by celestial bodies, including earth. Neither the Earth nor the Moon are significant sources of radio noise, so the body noise is also very low, at only 6K. However, the sun and gas giants can be significant sources of noise, so if they are within the beamwidth of your antenna, they may greatly increase noise.
This is the amount of noise added by the receiver antenna and amplification equipment. This is dependent on the tech level of the antenna and the quality of the ground station. Deep Space tracking stations generally have very low receiver noise. In this example, DSNTrackingStation only adds 30K worth of noise.
This is the sum of all noise sources. In this example, the total noise is very low, at 38.69K.
This is N0, or the noise density. This is a measure of how much noise power will be added to the signal per bandwidth used, at -183.90 dBm/Hz. More information can be found here.
This is the losses in the signal between the transmitter and receiver.
This is losses due to distance travelled (this will depend on the chosen radio band). In this case, traveling from the Moon to the Earth (404.97 Million meters), losses of 211.6 dB occour.
This is losses due to inaccurate antenna pointing. As mentioned in Antenna AoA and Antenna Elevation, the Apollo High Gain Antenna is only pointed 0.6 degrees away from the DSNTrackingStation and so suffers very minor losses (Tx losses of 0.1 dB), while the DSNTrackingStation always has perfect pointing and suffers no losses (Rx losses of 0.0 dB), so the total pointing loss is only 0.1 dB.
This is where all the information from the previous windows comes together to show the overall quality of the connection.
This is the calculation for the amount of power received at the receiving antenna. This is simple math, with the transmitter gain (30.3 dBi), transmitter power (30.0 dBm), and receiver gain (63.6 dBi) added together and subtracted from the losses (211.8 dB) to give a received power of -87.8 dBm.
This is the calculation for the amount of noise power received at the receiving antenna. The Noise Density (N0) found in the Noise section (-183.90 dB/Hz) multiplied by the bandwidth used (this will depend on the chosen radio band). In this example, the Channel Noise Power is -167.8 dBm.
This is the encoder used for error-correction. This depends on the tech level of the antennas, with the lowest-tech encoder of the pair being chosen to ensure backwards compatibility. Error-correction codes are very complex (see more here), but they are simplified for use in RealAntennas. First, the encoder name (Reed-Solomon 255/223). This isn't directly useful, but you can look it up if you want to know more about historical coding schemes. Then, the encoder rate (0.87). This describes how much of the bandwidth is consumed by by error-correction codes. A rate of 0.87 means only 87% of the bandwidth can be used to transmit data, with the remainder used by error-correction codes. Finally, the Eb/N0 (6.1). This is the energy per bit to noise power spectral density ratio, or how much stronger the signal needs to be than the noise in order to successfully detect it.
This is the Eb/N0, the amount of signal received by the receiver over the amount of noise received. The amount of channel noise power (-167.8 dBm) and the required encoder margin (6.1 dB) is subtracted from the received power (-87.8 dBm) to give the Eb/N0 (73.9). An Eb/N0 of 0 would indicate the signal is at the minimum power required for the receiver to detect it. In this example, the Eb/N0 is 73.9 times greater than the required minimum power, which means there is a very good connection.
This is the data rate (in bits/second) achieved. In this example, a connection of 577,170 bits per second (577.2 kbps) from the Apollo High Gain Antenna to the DSNTrackingStation is achieved
This is the range of valid rates the encoder can support. If the Eb/N0 does not support a connection at full speed, the transmission speed can be halved to increase Eb/N0, down to the minimum supported speed.
This is the number of halvings used. In this example, it is 0, because the connection can be supported at full speed.
You may notice that all of the fields are repeated a second time in the planner. This is because the connection needs to be calculated in both directions. All of the calculations are run a second time with the DSNTrackingStation taking the role of transmitter, and the Apollo High Gain Antenna taking the role of receiver. This is typically less important, since you generally care more about being able to transmit data back home, but you need a bi-directional link for a connection to be formed, so if the Tracking Station is unable to transmit to your vessel, you will not have a connection