Rádios econômicos que não sejam de 2,4 GHz para enxames de drones

Choosing Cost‑Effective Non‑2.4 GHz Radios for a 20‑Drone Master‑Slave Swarm

Recentemente, we received an inquiry from a UAV operator looking to implement a master–slave drone swarm with very specific requirements:

“Do you have any communication systems that should not work on 2.4 GHz for swarm 20 drones?
We are using master–slave configuration looking for a 4 km LOS and 1.5 km AGL height.
Looking for a cost-effective solution, video transmission is not required.
Is there any solution under 100 USD or below per unit? These are for target drones; they will be destroyed.
Há 19 slave drones which will be in a pattern and placed 5 meters apart.
The master drone will be 20 meters apart. Must be gas, non‑2.4 GHz.”

Let’s break down the requirements and explore practical, low-cost communication solutions for this scenario.

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Key Requirements

1. Master–Slave Swarm: 1 master + 19 slave drones.
2. Drone spacing: Slaves ~5 m apart; master ~20 m apart.
3. Communication range: Reliable 4 km LOS (line-of-sight) links.
4. Altitude: Até 1.5 km AGL.
5. Data type: Telemetry/control only — no video.
6. Frequency constraints: Must avoid 2.4 GHz.
7. Budget: Ideally ≤ $100 per unit, since drones are expendable.

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Technical Considerations

Frequency Band Trade-offs

Lower frequencies such as 433 MHz, 868/915 MHz, ou 1.2 GHz propagate farther and are more reliable than 2.4 GHz, making them ideal for long-range telemetry. These bands are commonly used in hobbyist and industrial UAV telemetry systems.

Range vs. Antenna and Power

UMA 4 km LOS link is achievable with moderate transmit power, good antennas, and clear LOS. Antenna height, ganho, and polarization are crucial for maintaining reliable connections.

Network Topology

In a star topology com 19 slaves, collision management is important. Using LoRa, ExpressLRS, or similar radios, you need to consider protocol design to avoid packet collisions and latency issues.

Regulatory Considerations

Frequency bands and transmit power are regulated by country. Always check local rules (FCC, ESTA, etc.) before deployment. This is particularly important for low-cost long-range radios.

Cost and Performance Trade-offs

While hobbyist modules can achieve 4 km LOS under ideal conditions for <$100, professional long-range telemetry radios often exceed $100. Testing is essential to validate performance in real operational conditions.

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Practical Options

1. Lora / SX127x Modules (868/915 MHz)
   • Pros: Very low cost ($30–$60 per unit), long-range in LOS, robust interference immunity.
   • Cons: Low data rates, potential duty cycle restrictions, longer latency.
2. 900 MHz Telemetry Radios / ExpressLRS Modules
   • Pros: Baixa latência, widely used in UAV control, robust link, can support multiple nodes.
   • Cons: Modules with guaranteed long-range may exceed $100; cheaper modules require careful setup and tuning.
3. 433 MHz / 1.2 GHz Modules
   • Pros: Excellent propagation, ideal for low-cost expendable drones.
   • Cons: Large antennas may be required, regulatory limits vary by region.

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Recommendations

• Prototype First: Test a small swarm (1 master + 3–5 slaves) to verify range, latency, and collision management.
• Choose the right protocol: Ensure the radio supports multiple slaves or implement a simple polling schedule.
• Optimize antennas: Proper placement, ganho, and polarization often have a bigger impact than transmit power.
• Stay legal: Follow local frequency and power regulations.

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Perguntas frequentes

Conclusão

For a cost-effective, non-2.4 GHz master-slave swarm, the most practical solutions are:

• LoRa/SX127x modules (868/915 MHz) for low-rate telemetry.
• 900 MHz telemetry radios / ExpressLRS for low-latency control.

Both approaches can fit a <$100 budget per drone in open-field LOS. Real-world performance depends on antennas, protocol design, and regulatory limits. UMA prototype test is essential before scaling to 20 drones.