COFDM 視訊發射機參數解釋

Complete Explanation of COFDM Video Transmitter Parameters

Understanding FREQ, 體重, FEC, 胃腸道, 地圖, 安泰信, 串口, 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 (螢幕顯示). A typical example might look like this:

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

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FREQ — Frequency

Full Name: 工作頻率
例子: FREQ: 830MHz

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

How it works:
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, 更好地穿透障礙物.
• 1.2 百萬赫, 2.4 百萬赫, 或者 5.8 GHz for short-distance, higher data rate transmission.

Impact:

• Lower frequency (例如, 700–900 MHz): Better penetration and longer range, ideal for drones or mobile units in urban areas.
• Higher frequency (例如, 5.8 百萬赫): 更高的吞吐量, 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: 頻道頻寬
例子: BW: 2MHz

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

Common values: 1 兆赫, 2 兆赫, 4 兆赫, 8 兆赫.

Explanation:

• 一個 wider bandwidth allows more data throughput, enabling higher-resolution or higher-frame-rate video.
• 一個 narrower bandwidth uses less spectrum and provides longer range and stronger penetration, but at the cost of data speed.

Example comparison:

帶寬	數據速率	範圍	Suitable For
1 兆赫	低的	最長	Low bitrate or SD video
2 兆赫	中等的	長的	HD video over long distance
4 兆赫	高的	中等的	High-quality HD or low-latency video
8 兆赫	非常高	短的	Close-range or line-of-sight applications

Practical Tip:
For drone or tactical applications, 2 兆赫 is often the best balance between range and quality.

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FEC — Forward Error Correction

Full Name: 前向糾錯
例子: FEC: 2/3

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

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

Interpretation:

• 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.

例子:
For long-distance drone transmission, FEC = 1/2 或者 2/3 is ideal.
For short-range, high-quality streaming, 你可以使用 3/4 或者 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: 保護間隔
例子: 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, 車輛, 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 (例如, 1/4): Better resistance to echoes, ideal for urban or complex terrain, but slightly reduces data rate.
• Shorter GI (例如, 1/32): Higher speed, suitable for open field or direct line-of-sight links.

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

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MAP — Mapping (調製類型)

Full Name: Constellation Mapping 或者 調製類型
例子: 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:

調製	Bits/Symbol	數據速率	Signal Tolerance
QPSK	2	低的	出色的
16QAM	4	中等的	緩和
64QAM	6	高的	低的

Practical Tip:
For long-range, 移動的, 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
例子: ATTEN: 0dB

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

How it works:

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

Effect:

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

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

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UART — Universal Asynchronous Receiver/Transmitter

例子: 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 波特率 — the communication speed between the transmitter and the controlling device.

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

目的:

• 參數配置 (頻率, 力量, 頻寬, 等等)
• Firmware upgrades
• Status feedback (訊號強度, 溫度, 等等)

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

例子: EVNE 或者 EVEN

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

選項:

• EVEN (EVNE): 奇偶校驗
• ODD: Odd parity
• 沒有任何: No parity bit

功能:
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 (頻率, 頻寬, FEC, 胃腸道, and modulation) match correctly.

If it shows “Unlocked” or “No Lock”:

• Check that both devices have the same 頻率, 頻寬, FEC, 胃腸道, 和 modulation.
• 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

範圍	Full Name	例子	功能	Key Effect
頻率	頻率	830 兆赫	Sets RF operating frequency	Must match TX/RX
體重	帶寬	2 兆赫	Defines channel width	Affects data rate & 範圍
FEC	前向糾錯	2/3	Adds redundancy for reliability	Balances speed & 穩定
胃腸道	保護間隔	1/32	減少多路徑幹擾	Shorter GI = higher speed
地圖	Modulation Mapping	QPSK	Sets modulation scheme	Impacts throughput & signal robustness
安泰信	衰減	0 分貝	Adjusts transmit power	Higher ATTEN = lower power
串口	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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常見問題解答 (常問問題)

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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, 體重, FEC, 胃腸道, 地圖, 安泰信, 串口, EVNE—affects how your transmitter balances between 範圍, 穩定, 和視頻品質.

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

• 頻率: within 700–900 MHz
• 體重: 2 兆赫
• FEC: 2/3
• 胃腸道: 1/16
• 地圖: QPSK
• 安泰信: 0 分貝

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