Quick Answer
Antenna choice makes or breaks long-range drone telemetry. Stock whip antennas give you 100m to a few kilometres. A directional patch or helical antenna on your ground station can push that to 15km or more. At 868 or 900MHz, line of sight is the single biggest factor, and circular polarisation helps when your drone banks and turns.
Antenna Types for Drone Telemetry
Telemetry radios like the Microhard V2 telemetry radio operating at 868 or 900MHz rely on antennas to turn radio energy into a usable signal. The antenna you pick determines range, reliability, and how much signal you keep when the drone is not perfectly level.
| Antenna Type | Polarisation | Typical Gain | When to Use |
|---|---|---|---|
| Monopole whip (stock) | Vertical linear | 2 dBi | Short range, general flying |
| Patch | Vertical linear | 6-12 dBi | Ground station, medium-long range |
| Helical | Circular (RHCP/LHCP) | 3-12 dBi | Tracking manoeuvring drones |
| Yagi | Linear | 10-15+ dBi | Fixed point-to-point links |
A monopole whip is omnidirectional. It radiates in all horizontal directions, which is convenient but wastes power pointing signal at the ground and sky. A patch antenna concentrates that energy into a cone in one direction, boosting range significantly. A helical adds circular polarisation, which is useful because a drone in flight is rarely perfectly upright. When a linear antenna tilts 45 degrees, you lose around 3dB of signal. Circular polarisation maintains a more consistent link through those angle changes.
Higher gain sounds better, and it is for range, but the beam width narrows. A 12 dBi patch might have a 30-degree beam. Point it slightly off and your signal drops fast. For a manually aimed ground station, 6 to 9 dBi is usually the sweet spot between range and usability.
Connector Types: SMA and RP-SMA
RFD modems use RP-SMA connectors. The "RP" stands for Reverse Polarity, meaning the centre pin is on the socket rather than the plug compared to standard SMA. If you plug a standard SMA antenna into an RP-SMA socket (or vice versa) you get a poor electrical connection and terrible performance, even though the threads fit. Always match the connector type to the modem specification. Check the datasheet or product page before buying antennas.
Adaptors exist, but each one in the signal path introduces a small loss. Use the right connector from the start.
Factors That Affect Range
Line of sight is king. At 868 and 900MHz, the signal does not meaningfully pass through buildings, hills, or dense tree cover. A ridgeline between your ground station and the drone will kill the link regardless of how much power you push. Plan your flight paths with terrain in mind. Flying higher gives the signal a clearer path back to the ground station, which is why long-range pilots climb before heading out.
Ground plane matters for monopole antennas. A quarter-wave whip needs a reflective surface beneath it to form a proper radiation pattern. On an aircraft, the battery, flight controller, and frame can act as a ground plane, but results vary. A ground station whip on a large metal surface (like a car roof) performs noticeably better than one sitting on a wooden table.
RF noise from urban environments, other radio equipment, and even high-voltage power lines can reduce your effective range. Rural flat land with clear sight lines gives the best results.
How to Range Test Properly
Do not just fly out until you lose signal and call it your maximum range. A proper range test follows a methodical approach:
- Start short. Verify your link at 100m with RSSI and packet loss figures. Record your baseline.
- Increase distance in steps. Fly 500m, then 1km, then 2km. Log RSSI, noise floor, and signal-to-noise ratio at each point.
- Watch your metrics. RSSI above -100dBm is solid. Below -110dBm is marginal and unreliable for telemetry.
- Test altitude. Fly the same distance at 50m, 100m, and 200m altitude. The results can differ dramatically.
- Set a failsafe. Always configure return-to-home on link loss before pushing range limits.
What to Buy
- Microhard V2 Telemetry Radio (P900/P400) - high-power mesh link for serious range
- Browse the full RFdesign telemetry modem range for RFD900x and RFD868x options
- Wireless and telemetry accessories - cables, adaptors, and mounting hardware
Related Reading
- RFdesign Module Comparison: 868x vs 868ux vs 900x vs 900ux
- Building a Complete Long-Range Drone Data Link
Frequently Asked Questions
Q: Can I use my 5.8GHz FPV video antenna on a telemetry radio?
A: No. Antennas are tuned to a specific frequency. A 5.8GHz antenna will perform very poorly at 868 or 900MHz. You need an antenna designed for your telemetry frequency band.
Q: Do I need circular polarisation for telemetry?
A: It helps, but it is not essential. If your drone mostly flies level and straight, a patch antenna is simpler and more efficient. Circular polarisation shines when the drone is aggressively manoeuvring at range.
Q: How far can I realistically fly with stock antennas?
A: In an urban environment with interference, expect a few hundred metres. In flat rural terrain with clear line of sight, stock 2 dBi whips can reach 1 to 3km. Switch to a directional ground station antenna and those numbers climb considerably. See our long-range communication guide for more detail.