Antenna Planning Guide

Before reading this guide, make sure you've read the quick start guide to RealAntennas. There are several important basics to understand about RealAntennas before you start using the planner.

This guide is for the new planning GUI in RA 2.1. If you are familiar with the old planning GUI there won't be many surprises here.

To access the antenna planning GUI find and click the antenna planning button under the RealAntennas tab of the part action window (the right click menu, hereafter PAW).

1. Active Transmission Time This line will only appear if you have installed Kerbalism alongside RealAntennas. It is the percentage of time that you believe your craft will spend actively transmitting. The Kerbalism planner can then give the EC consumption rate of your antenna without assuming it will constantly be actively transmitting.
2. Antenna Planning Will open a new antenna planning window each time the button is pressed. It is explained further below.

This menu has all of the knobs for antenna planning and there's a lot to go over. Lets run everything down from top to bottom

The default behavior is to set the peer to the most sensitive ground station on the home body. However, there are plenty of situations where that connection is not the one you are concerned about. In those cases you will use the antenna planning GUI to select the peer.

1. Ground Station TechLevel This shows you the TechLevel of your existing ground stations, as well as the TechLevel of the ground station you are planning against. The tech level for the ground station you are planning against is adjustable with the adjacent slider. Useful when designing a mission that will not work with existing ground stations, but may work with upgraded ground stations in the future.
2. Antenna Selection This section of the planning GUI is where you select two antennas to plan around. You select the Primary and the Peer (Fixed) antennas from the lists in the respective columns. You can cycle each column between displaying vessel and ground station antennas by pressing the cycle button immediately below the GUI text Primary and Peer. You can see the specific antenna selected for Primary and Peer (Fixed) displayed below in the Parameters section. Note that you are free to select any antenna on an existing craft, or any antenna on an open craft file in the VAB/SPH.
3. Remote Body Presets These radio buttons are a convenient option to pick from if you wish to plan connections to a specific celestial body. Simply pick a button corresponding to a celestial body and the planner will automatically set the min and max planning distances to the min and max distance between the home body and the selected celestial body. If you do not want to set the planning distance to a celestial body then there is no need to make a selection here.
4. Parameters This is where you can see the selected primary and peer (fixed) antenna as well as set the min and max planning distances between them. You can set the distances by entering a number and selecting a radio button for the desired unit of length (kilometer,megameter,etc). It will also show you the planning result at the given distances as transmit (Tx) and receive (Rx) data rates in bits per second(bps)). So long as the Tx and Rx are both greater than zero at a given distance then you will have a connection. If either Tx or Rx is reported as zero you will not have a connection at the given distance. Note that manual changes to the distances will not automatically be reflected in the Tx/Rx rates. If you have manually changed these values you will want to press Plan! below afterwards.
5. Plan! Press this button when you want to know the result of attempting a connection between the two selected antennas at the given distances. The adjacent toggle for Show Details will open the rather detailed debug GUI in a new window if enabled when you press Plan!

In this first example, the antenna will be representative of an early lunar probe in Real Solar System. The planning peer is set to the default, so the calculations will be in reference to our most sensitive ground stations. The planning altitude is set to the approximate maximum separation between the Earth and the Moon (400,000 km). Looking at the rates for Transmit/Receive, we see there will not be a connection at this altitude. Remember that the rate for both transmit and receive must be greater than zero to establish a connection.

In the next example, the situation will be more complicated, but the planning will still be quite simple. We'll look at craft to craft communications at relatively short distances. In this scenario, we're planning a relay network of four satellites to reduce communication drop outs with craft in low orbits. This network will consist of four evenly spaced satellites around the Earth in circular orbits about 3400 km above the surface. At the selected tech level, we have the option to use S-band, but opt to use UHF because there are more ground stations that can receive at that frequency.

We're using the built in antenna on the procedural avionics part as a stand in for the craft in LEO, and the Communotron 16 for the relay. Note that the built in antenna on the procedural avionics is slightly worse (1.5 dBi vs 3.0 dBi) than the extendable Communotron 16.

The planning altitude is set to a bit more than the distance from a given relay to a satellite in LEO on the limb of the Earth as seen from our relay. We see that with these settings, both transmit and receive are greater than zero. Therefore the relay can talk to craft in LEO with a built in omni and 30 dBm transmit power. We can also see that for spacecraft directly underneath the relay a much higher data rate can be established.

Note that we do not check if the relays can talk to the ground stations. Due to the considerable sensitivity of ground stations, this is a given. A more interesting question is whether relays can talk to relays. The distance between relays is more than 12,000 km but the link will have the higher gain Communotron 16 on both ends. In this case it works out that relays can talk to relays. If you want to check this, simply select the Communotron 16 as both the primary and the peer antenna.

Finally, here is an example of planning interplanetary communications. The radio button for Venus has been pressed, so the min and max planning distance are set to the minimum and maximum separation between the Earth and Venus. At minimum separation the antenna can establish a connection back to Earth because both transmit and receive are above zero (2.6 Kbps and 82.5 Kbps respectively). At maximum separation there will not be a connection because transmit and receive are not both greater than zero.