A Primer on RealAntennas

Written for RP-1 v4.3.0.0.

TL;DR

General Advice

• Match the band of your peer antenna/station.
  • Higher frequencies (S, X) are generally better for longer ranges with higher data rates, since they focus better.
  • Lower frequencies (VHF) are generally better for shorter ranges when you just want any connection at all.
• Every 3dB of extra gain/power gets 2x data rate for the same range.
• Every 6dB of extra gain/power gets 2x range for the same data rate.
• If the range doubles but the gain/power stays the same, the data rate becomes 1/4 of what it was.
• The Power (Active) field tells you how much power you need to transmit at the maximum possible data rate.
  • If nothing is being transmitted, it draws the idle power (Power (Idle)).
  • Otherwise, it linearly interpolates between the two according to the portion of the maximum possible data rate being used.
• The DSN (Madrid, Canberra, Goldstone) is always visible above 30Mm.
• Only TL2+ antennas can relay.
• Higher tech levels decrease power/bit (but may increase idle power).
• Higher tech levels upgrade your ground stations, which increases their effective ange.

Band Choice

• Higher frequency bands have the following benefits:
  • High bandwidth, which increases the maximum attainable data rate you can get.
  • Higher gain for the same dish, which means you can use less power transmitting.
  • Higher gain at the receiver, which also means you can use less power transmitting.
• Higher frequency bands have the following downsides:
  • S, X, Ku and Ka bands have less stations on Earth, so you can only use them consistently past GEO.
  • Higher path loss [ by a fixed dB amount, based on log(frequency) ].
  • Slightly higher atmospheric attentuation (?). This usually doesn't matter.
  • Lower beamwidth for the same dish, so if your intended targets are spread out you can't talk to all of them at once.
  • Higher minimum data rate to connect, which increases the minimum dB you need to get any connection if you don't care about data rate.

Dishes

• Bigger dishes have higher gain but lower beamwidth.
• Dishes have a 3dB cone (half beamwidth from centre) and a 10dB cone (full beamwidth from centre).
  • If your target is inside the bright magenta cone, you get at most 3dB of pointing losses.
  • If your target is inside the dark purple cone, you get at most 10dB of pointing losses.
  • Outside of that, there is no connection whatsoever.
• Dishes can be targeted via the Antenna Targeting menu independent of their physical facing.