Объяснение параметров видеопередатчика COFDM

Complete Explanation of COFDM Video Transmitter Parameters

Understanding FREQ, ЧБ, FEC, GI, КАРТА, ВНИМАНИЕ, УАРТ, EVNE, and Channel Lock

When customers receive a COFDM video transmitter, they often notice a set of technical parameters displayed on the screen or OSD (Экранное меню). A typical example might look like this:

For many users, especially those who are not radio engineers, these values look confusing. Однако, each of them plays a crucial role in how the COFDM transmitter sends stable, low-latency video over long distances.
This article explains all these parameters in detail, what they stand for, and how to adjust them correctly for your application — whether you are using COFDM transmitters for drones, транспортные средства, or tactical video systems.

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FREQ — Frequency

Full Name: Operating Frequency
Пример: FREQ: 830MHz

This shows the RF center frequency used by the transmitter. It defines where in the radio spectrum the video signal is transmitted.

Как это работает:
The transmitter modulates the digital video signal into an RF carrier. The receiver must tune to the exact same frequency to demodulate and decode the video.

Typical frequency ranges:

• 300–900 MHz for long-range, лучшее проникновение через препятствия.
• 1.2 ГГц, 2.4 ГГц, или 5.8 GHz for short-distance, higher data rate transmission.

Impact:

• Lower frequency (например, 700–900 МГц): Better penetration and longer range, ideal for drones or mobile units in urban areas.
• Higher frequency (например, 5.8 ГГц): Более высокая пропускная способность, but shorter range and more easily blocked by buildings.

Practical Tip:
Always make sure the transmitter and receiver use exactly the same frequency. Even a 1 MHz difference will cause the receiver to lose lock.

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BW — Bandwidth

Full Name: Пропускная способность канала
Пример: BW: 2MHz

Bandwidth defines how wide the transmitted signal is on the frequency spectrum. It determines how much data (видео + контроль) can be transmitted at once.

Common values: 1 МГц, 2 МГц, 4 МГц, 8 МГц.

Explanation:

• А wider bandwidth allows more data throughput, enabling higher-resolution or higher-frame-rate video.
• А narrower bandwidth uses less spectrum and provides longer range and stronger penetration, but at the cost of data speed.

Example comparison:

Пропускная способность	Скорость передачи данных	Диапазон	Suitable For
1 МГц	Низкий	Самый длинный	Low bitrate or SD video
2 МГц	Середина	Длинный	HD video over long distance
4 МГц	Высокий	Середина	High-quality HD or low-latency video
8 МГц	Очень высокий	Короткий	Close-range or line-of-sight applications

Practical Tip:
For drone or tactical applications, 2 МГц is often the best balance between range and quality.

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FEC — Forward Error Correction

Full Name: Прямое исправление ошибок
Пример: FEC: 2/3

FEC adds redundant information to the transmitted signal so that the receiver can detect and correct errors caused by noise, вмешательство, or weak signal conditions.

Typical ratios: 1/2, 2/3, 3/4, 5/6.

Интерпретация:

• 1/2 → Strong error protection (half of the data is error correction).
• 5/6 → Weaker error protection but higher throughput.

Effect on performance:

• Lower FEC ratio = more reliable link, less data rate.
• Higher FEC ratio = faster data rate, needs strong signal.

Пример:
For long-distance drone transmission, FEC = 1/2 или 2/3 is ideal.
For short-range, high-quality streaming, ты можешь использовать 3/4 или 5/6.

Practical Tip:
If your video occasionally freezes or breaks under weak signal, try lowering FEC to 1/2.

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GI — Guard Interval

Full Name: Защитный Интервал
Пример: GI: 1/32

A guard interval is a short pause inserted between COFDM symbols to prevent inter-symbol interference caused by reflections or multipath signals.

Why it matters:
In real-world environments, radio signals bounce off walls, транспортные средства, or the ground, creating multiple delayed copies of the same signal. Without a guard interval, these reflections would overlap and corrupt the next symbol.

Typical values: 1/4, 1/8, 1/16, 1/32.

Effect:

• Longer GI (например, 1/4): Better resistance to echoes, ideal for urban or complex terrain, but slightly reduces data rate.
• Shorter GI (например, 1/32): Higher speed, suitable for open field or direct line-of-sight links.

Пример:
If you’re transmitting through buildings or around corners, set GI to 1/8 или 1/16.
If it’s a clear open field, 1/32 works fine.

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MAP — Mapping (Тип модуляции)

Full Name: Constellation Mapping или Тип модуляции
Пример: MAP: QPSK

MAP defines how binary data (0s and 1s) are mapped onto the carrier wave — essentially, which modulation scheme is used.

Common modulation types:

• КФСК (Quadrature Phase Shift Keying): Transmits 2 bits per symbol; very stable, suitable for weak signals and long range.
• 16QAM: Transmits 4 bits per symbol; higher throughput, but needs strong signal.
• 64QAM: Transmits 6 bits per symbol; maximum data rate but most sensitive to noise.

Effect:

модуляция	Bits/Symbol	Скорость передачи данных	Signal Tolerance
КФСК	2	Низкий	Отличный
16QAM	4	Середина	Умеренный
64QAM	6	Высокий	Низкий

Practical Tip:
For long-range, мобильный, or drone systems, КФСК is the best option.
If your system is fixed and the signal is strong, 16QAM can improve throughput.

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ATTEN — Attenuation

Full Name: Transmit Power Attenuation
Пример: ATTEN: 0dB

This parameter adjusts the output RF power передатчика.
Attenuation simply means how much the signal is reduced before transmission.

Как это работает:

• 0 дБ = full output power (no reduction).
• Higher dB value = signal power reduced by that amount.

Effect:

• Lower attenuation (например, 0 дБ): maximum power, longest range.
• Higher attenuation (например, 10 дБ): reduced power, useful for short-range testing or avoiding interference.

Пример:
When testing indoors, set ATTEN to 10–20 dB to prevent saturating the receiver.
For actual flight or field use, использовать 0 дБ to maximize range.

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UART — Universal Asynchronous Receiver/Transmitter

Пример: UART: 19200

UART refers to the serial communication interface used to configure or control the COFDM module through a data cable or host controller.

19200 represents the скорость передачи данных — the communication speed between the transmitter and the controlling device.

Common baud rates: 9600, 19200, 38400, 115200.

Цель:

• Конфигурация параметров (частота, власть, пропускная способность, и т. д.)
• Firmware upgrades
• Status feedback (signal strength, температура, и т. д.)

Practical Tip:
When connecting to a PC or microcontroller, ensure both ends use the same baud rate and parity settings (see “EVNE” below).

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EVNE — Even Parity

Пример: EVNE или EVEN

This refers to the parity bit used in UART communication. It’s a simple form of error detection that ensures data integrity.

Параметры:

• EVEN (EVNE): Even parity
• ODD: Odd parity
• НИКТО: No parity bit

Функция:
Parity bits help detect transmission errors during serial communication.
If the parity doesn’t match between the transmitter and the connected device, data may appear as random symbols.

Practical Tip:
Set the same parity (EVEN/ODD/NONE) on both devices to ensure stable communication.

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Channel Lock

Display Example: “Channel Lock” or “Lock OK”

This message indicates that the receiver has successfully locked onto the transmitter’s COFDM signal — meaning all parameters (частота, пропускная способность, FEC, GI, and modulation) match correctly.

If it shows “Unlocked” or “No Lock”:

• Check that both devices have the same частота, пропускная способность, FEC, GI, и модуляция.
• Verify antennas are properly connected.
• Ensure signal strength is above the threshold.

Once “Channel Lock” appears, the receiver can decode the video and output stable image.

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Summary Table

Параметр	Full Name	Пример	Функция	Key Effect
ЧАСТОТА	частота	830 МГц	Sets RF operating frequency	Must match TX/RX
ЧБ	Пропускная способность	2 МГц	Defines channel width	Affects data rate & диапазон
FEC	Прямое исправление ошибок	2/3	Adds redundancy for reliability	Balances speed & стабильность
GI	Защитный Интервал	1/32	Уменьшает многолучевые помехи	Shorter GI = higher speed
КАРТА	Отображение модуляции	КФСК	Sets modulation scheme	Impacts throughput & signal robustness
ВНИМАНИЕ	Затухание	0 дБ	Adjusts transmit power	Higher ATTEN = lower power
УАРТ	Последовательный интерфейс	19200	Communication port	Used for control & настраивать
EVNE	Четный паритет	EVEN	UART parity setting	Prevents serial errors
Channel Lock	—	Locked/Unlocked	RF synchronization status	Must lock before video output

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Часто задаваемые вопросы (Вопросы-Ответы)

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Заключение

Understanding these COFDM parameters is essential for getting the best performance from your wireless video system.
Each setting—FREQ, ЧБ, FEC, GI, КАРТА, ВНИМАНИЕ, УАРТ, EVNE—affects how your transmitter balances between диапазон, стабильность, and video quality.

For most long-range drone and tactical video applications, the following configuration is recommended:

• ЧАСТОТА: within 700–900 MHz
• ЧБ: 2 МГц
• FEC: 2/3
• GI: 1/16
• КАРТА: КФСК
• ВНИМАНИЕ: 0 дБ

With correct configuration and antenna alignment, COFDM technology can provide robust, с низкой задержкой, non-line-of-sight video transmission in challenging environments.