Por qué los enlaces COFDM deberían evitar las frecuencias DVB-T?

Q: 3. Which frequencies are legal for drones and mobile video?

For civil and commercial use, ISM bands such as 2.4 GHz and 5.8 GHz are the best legal options. Lower frequencies (1.2–1.4 GHz or 300–900 MHz) may be used only under licensed or military conditions.

Why COFDM Links Should Avoid DVB-T Frequencies in Europe

COFDM (Multiplexación por división de frecuencia ortogonal codificada) is a robust technology used for wireless video transmission. Its strong resistance to multipath interference makes it ideal for drones, vehículos, and tactical surveillance systems.

sin embargo, when operating in Europe, es esencial para avoid using frequencies assigned to DVB-T and DVB-T2 digital television broadcasting.
Even though both systems rely on the same COFDM modulation principle, their applications, potencia de transmisión, and regulatory control are completely different.

Este artículo explica why COFDM links should avoid DVB-T frequencies, the consequences of overlap, and the recommended frequency bands for reliable and legal operation.

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1. Understanding DVB-T and DVB-T2

DVB-T (Digital Video Broadcasting – Terrestrial) y DVB-T2 are Europe’s standard formats for terrestrial digital TV broadcasting.

They occupy specific frequency bands:

VHF Band III: 174 – 230 megahercio
UHF Bands IV–V: 470 – 694 megahercio

Some regions previously extended up to 862 megahercio, pero el 700 MHz and higher range is now mostly reallocated to 4G/5G mobile networks. These frequency ranges are tightly regulated and reserved for high-power public television broadcasting.

2. Why COFDM Transmitters Must Avoid DVB-T Frequencies

(1) Avoid Interference with Public Broadcasts

COFDM video transmitters working within 470–694 MHz may interfere with DVB-T reception nearby.
Because DVB-T transmitters use tens of kilowatts of power, even a low-power private transmitter can cause:

pixelation or signal loss on TV screens,
temporary blackouts of digital channels,
complaints and enforcement actions by local authorities.

Agencies such as Ofcom (Reino Unido), ANFR (Francia), y BNetzA (Alemania) strictly prohibit unauthorized signals within DVB-T frequencies.

(2) Prevent Receiver Overload and Self-Interference

Even if your COFDM system uses a different channel within the same band, strong DVB-T broadcast signals can saturate the receiver front end.
This leads to:

drastically reduced transmission distance,
unstable decoding,
frequent image freezing or disconnection.

De este modo, using DVB-T frequencies not only risks legal issues but also degrades your own link quality.

(3) Comply with Spectrum Regulations

Under BUSCAR ES 300 744 (DVB-T) y EN 302 755 (DVB-T2), the 470–694 MHz range is reserved exclusively for digital terrestrial television.
Operating COFDM systems in this range without authorization is illegal in most European countries and can result in fines or equipment seizure.

3. Recommended Frequency Bands for COFDM Links

Solicitud	Recommended Band	Rango de frecuencia	Notas
UAV / Drone Video	ISM Band	2.4 GHz / 5.8 GHz	License-free, globally accepted
Ground Surveillance	Licensed Band	1.4 GHz / 2.3 GHz	Rendimiento equilibrado, license required
Táctico / Police Use	Sub-GHz Band	300 – 900 megahercio	Fuerte penetración, restricted access
Civil / Demo Use	ISM Band	2.4 GHz / 5.8 GHz	Best for demonstrations and non-critical use

Using these ranges prevents interference and ensures compliance with local spectrum laws.

4. DVB-T/T2 Frequency Chart for Europe

Banda	Rango de frecuencia (megahercio)	Primary Use
VHF Band III	174 – 230	Regional DVB-T broadcasting
UHF Bands IV–V	470 – 694	Core DVB-T/T2 range
Arriba 700 megahercio	694 – 862	Now used for LTE/5G mobile networks

For COFDM transmitters in Europe:

Avoid: 174–230 MHz and 470–694 MHz
Usar: 1.2 GHz, 2.4 GHz, o 5.8 GHz bands for safe, interference-free video transmission.

5. Engineering Recommendations

Add Selectable Frequency Options
Allow users to manually switch to ISM bands or licensed frequencies to stay within legal limits.
Integrate RF Filters
Bandpass filters help block powerful DVB-T signals and protect receiver sensitivity.
Provide Frequency Planning Tools
Offer frequency charts and planning guides for each country to help users avoid restricted DVB-T/T2 ranges.
Include Legal Warnings in Manuals
“Operation within DVB-T or DVB-T2 frequency ranges is prohibited in Europe. Use ISM or authorized frequencies only.”

6. Conclusión

COFDM offers exceptional reliability for wireless video transmission, pero frequency selection is critical.
En Europa, DVB-T/T2 occupies the 470–694 MHz band (and parts of 174–230 MHz) for digital TV broadcasting. Using these frequencies for COFDM video can cause interference, instability, and legal violations.

To ensure stable and compliant performance:

Avoid DVB-T/T2 broadcast ranges,
Use ISM or licensed frequency bands,
Always verify local spectrum regulations before deployment.

Following these principles ensures clear video, comunicación estable, and compliance across Europe.

Preguntas frecuentes (Preguntas más frecuentes)

1. Can I use 500 MHz for my COFDM transmitter?

No. 500 MHz falls inside the DVB-T broadcasting band (470–694 MHz). Transmitting there may interfere with digital television and is not legally allowed without authorization.

2. What happens if I use a DVB-T frequency accidentally?

You may disrupt public TV reception and attract enforcement action from local authorities. It can also cause heavy interference to your own COFDM receiver, reducing range and image quality.

3. Which frequencies are legal for drones and mobile video?

For civil and commercial use, ISM bands such as 2.4 GHz y 5.8 GHz are the best legal options. Lower frequencies (1.2–1.4 GHz or 300–900 MHz) may be used only under licensed or military conditions.