Antennas

The antennas are a key component for any radio link solution and the same for radio waves are applicable here. The right combination depends on the objectives, like short-range (all-around flight) or long-range flight for more advanced pilots. A good starting point is the default antennas for the wifi cards at the workbench (omnidirectional), once you get confident with the system during a line of sight and short flights, you can move with directional antennas.

As nothing is free, changing your antennas is a trade-off, while omnidirectional antennas give you autonomy to fly around your position, these antennas offer limited range, on the other side directional antennas concentrate the radiated pattern and allow a long-range at the cost of the need of pointing the antennas precisely, in other words, more antenna gains more directional. For the high directive antenna, add components like trackers are recommended to keep always pointing the main antenna pattern lobule to the aircraft.

5 TIPs for Antennas

  1. Make sure you have proper wiring and you have followed all previous sections, wrong connections can lower your range or destroy your radio link.

  2. Start simple using Omni antennas, and move with directional ones as you get more experience.

  3. Make sure you use the same polarization on both sides, Vertical/Vertical, Horizontal/Horizontal. The cross-polarization can work but you will lose 3dB (half of the power).

  4. Lower bands like 2.4GHz can benefit the range, however, in some areas, this band is highly polluted and you may consider 5.8GHz. Try changing also the channels in the selected band.

  5. When using directional antennas (meant for ground side), always aligned with the airside, consider using ATT (automatic antenna tracker). Omnidirectional antennas are always recommended in the Airside.

The below link explains how the video quality is impacted under different scenarios. https://www.youtube.com/watch?v=T78JRAELjec

Antenna Hardware

BrandAntennaPolarizationFrequency GHzLink *

DYI

PCB Maple

Omni Vertical

5.2-5.3

Maple

Flat Panel FY-05A

Directional Vertical

5.8

Maple

Planar Antenna

Directional Vertical

5.8

Interline

Panel

Directional Vertical

5.8

uuustore

Flat Panel Antenna

Directional Vertical

5.8

Aomway

Biquad

Directional Vertical

5.8

DYI

Biquad Yagi Antenna

Directional

2.4

DYI

PCB patch array

Directional

2.4 / 5.8

*Links are only for reference purposes. It will be added more as users report, check the connector type in order to make sure it will fit to your wifi card.

Range Calculation

A typical question is related to the maximum range, link budget or system range have relation to three main elements: Transmitter power, Antenna gains, and Receiver sensitivity. The next formula can be used to calculate this:

R_km = 10 ^ ( ( RF_HW - LM - 32.44 - 20*log10(f_MHz) ) / 20 )

RF_HW = P_TX + G_TX + G_RX - S_RX

where:

R_km is the transmission range in km f_MHz is the frequency in MHz LM is the desired system Link Margin in dB 32.44 is the Friis constant for solving with units of km and MHz above RF_HW represents the RF Hardware (Radio / Antenna) parameters in dB P_TX is the Tx power in dBm G_TX is the Tx antenna gain in dBi G_RX is the Rx antenna gain in dBi S_RX is the Rx Sensitivity in dBm

Ground Side antenna / GainAir Side antenna / GainFrequency GHzPower TX mWTheoretical range Km *Notes

Maple 5dB Omni / 5dBi

Maple 5dBi Omni / 5dBi

5.2GHz

200

2.9

Excellent upgrade for default antennas

Flat Panel Direct / 14dBi

Maple 5dBi / 5dBi

5.2GHz

200

8.2

Directional antenna with ATT

Planar Direct / 17dBi

Omni / 5dBi

5.8GHz

500

16.37

Directional antenna high range ATT

*Network card receiving sensitivity approx. -93dBm. Link margin assumed 10 dB

To understand the impact in range against the transmitter power, the below logarithmic graph shows some calculations using different antenna sets:

range vs power graph

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