COFDM Video Transmitter Parameters Explained

Complete Explanation of COFDM Video Transmitter Parameters

Understanding FREQ, BW, FEC, GI, 地図, 出席してください, UART, 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 (オンスクリーンディスプレイ). A typical example might look like this:

For many users, especially those who are not radio engineers, these values look confusing. しかし, 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, 車両, or tactical video systems.

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FREQ — Frequency

Full Name: 動作周波数
Example: FREQ: 830MHz

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

仕組み:
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, better penetration through obstacles.
• 1.2 GHz, 2.4 GHz, または 5.8 GHz for short-distance, higher data rate transmission.

Impact:

• Lower frequency (例えば, 700–900MHz): Better penetration and longer range, ideal for drones or mobile units in urban areas.
• Higher frequency (例えば, 5.8 GHz): Higher throughput, 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: チャネル帯域幅
Example: BW: 2MHz

Bandwidth defines how wide the transmitted signal is on the frequency spectrum. It determines how much data (ビデオ + コントロール) can be transmitted at once.

Common values: 1 メガヘルツ, 2 メガヘルツ, 4 メガヘルツ, 8 メガヘルツ.

説明:

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

Example comparison:

帯域幅	データレート	範囲	Suitable For
1 メガヘルツ	低い	最長	Low bitrate or SD video
2 メガヘルツ	中くらい	長さ	HD video over long distance
4 メガヘルツ	高い	中くらい	High-quality HD or low-latency video
8 メガヘルツ	非常に高い	短い	Close-range or line-of-sight applications

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

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FEC — Forward Error Correction

Full Name: 前方誤り訂正
Example: FEC: 2/3

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

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

解釈:

• 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.

Example:
For long-distance drone transmission, FEC = 1/2 または 2/3 is ideal.
For short-range, high-quality streaming, you can use 3/4 または 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: ガードインターバル
Example: 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:
現実世界の環境では, radio signals bounce off walls, 車両, 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 (例えば, 1/4): Better resistance to echoes, ideal for urban or complex terrain, but slightly reduces data rate.
• Shorter GI (例えば, 1/32): Higher speed, suitable for open field or direct line-of-sight links.

Example:
If you’re transmitting through buildings or around corners, set GI to 1/8 または 1/16.
If it’s a clear open field, 1/32 正常に動作します.

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MAP — Mapping (変調方式)

Full Name: Constellation Mapping または 変調方式
Example: 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:

• QPSK (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:

変調	Bits/Symbol	データレート	Signal Tolerance
QPSK	2	低い	素晴らしい
16QAM	4	中くらい	適度
64QAM	6	高い	低い

Practical Tip:
For long-range, 携帯, or drone systems, QPSK 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
Example: ATTEN: 0dB

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

仕組み:

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

Effect:

• Lower attenuation (例えば, 0 dB): 最大出力, longest range.
• Higher attenuation (例えば, 10 dB): reduced power, useful for short-range testing or avoiding interference.

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

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UART — Universal Asynchronous Receiver/Transmitter

Example: 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 ボーレート — the communication speed between the transmitter and the controlling device.

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

目的:

• パラメータ設定 (頻度, 力, 帯域幅, 等)
• Firmware upgrades
• Status feedback (信号強度, 温度, 等)

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

Example: EVNE または EVEN

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

オプション:

• EVEN (EVNE): 偶数パリティ
• ODD: Odd parity
• なし: No parity bit

関数:
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 (頻度, 帯域幅, FEC, GI, and modulation) match correctly.

If it shows “Unlocked” or “No Lock”:

• Check that both devices have the same 頻度, 帯域幅, FEC, GI, そして 変調.
• 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

パラメータ	Full Name	Example	関数	Key Effect
周波数	周波数	830 メガヘルツ	Sets RF operating frequency	Must match TX/RX
BW	帯域幅	2 メガヘルツ	Defines channel width	Affects data rate & 範囲
FEC	前方誤り訂正	2/3	Adds redundancy for reliability	Balances speed & 安定性
GI	ガードインターバル	1/32	Reduces multipath interference	Shorter GI = higher speed
地図	変調マッピング	QPSK	Sets modulation scheme	Impacts throughput & signal robustness
出席してください	減衰	0 dB	Adjusts transmit power	Higher ATTEN = lower power
UART	Serial Interface	19200	Communication port	Used for control & 設定
EVNE	Even Parity	EVEN	UART parity setting	Prevents serial errors
Channel Lock	—	Locked/Unlocked	RF synchronization status	Must lock before video output

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よくある質問 (よくある質問)

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結論

Understanding these COFDM parameters is essential for getting the best performance from your wireless video system.
Each setting—FREQ, BW, FEC, GI, 地図, 出席してください, UART, EVNE—affects how your transmitter balances between 範囲, 安定性, and video quality.

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

• 周波数: within 700–900 MHz
• BW: 2 メガヘルツ
• FEC: 2/3
• GI: 1/16
• 地図: QPSK
• 出席してください: 0 dB

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