Wire & Cable (四) 我該買什麼線 ? (搬家文 from yahoo blog , Day1)

(以下圖文內容皆取材自 Belden 的技術文章)

即便做完所有的討論 , 問題還是存在 : 要如何為適當場合選用適當的線 ? 當把重要參數考慮進去, 面對不同的應用情形時, 下面會是一個有用的參考 .

( 為了避免翻譯誤差,  細項皆以原文呈現 )

需要類比音頻線材時 ......

低電容

        1. 50 pF/ft. for short runs under 100 ft.

        2. 30 pF/ft. for longer runs up to 500 ft.

        3. 25 pF/ft for longer runs up to 750 ft.

        4. 13 pF/ft. for runs over 1000 ft. or where ultimate performance is desired

低電阻

         1. 26 AWG for short runs under 100 ft. where ruggedness is not an issue

         2. 24 AWG for runs up to 1000 ft.

         3. 22 AWG for runs over 1000 ft. or where ruggedness is essential

低串音 (crosstalk)

         1. Foil shields for RF protection

         2. Braid shields for low self-noise and protection 1 kHz to 50 MHz

當有 AES/EBU 數位音頻絞線對需求時 ......

Specific impedance 110 ohm

         1. May vary between 88 and 132

低電容

         1. Below 20 pF/ft.

         2. Most AES pairs are 13 pF/ft.

低電阻

         1. Gage size a factor due to skin effect

         2. 24 AWG is most common

         3. 22 AWG can go about 10% farther

適度串音 (Moderate crosstalk)

         1. Only 30dB required

         2. Even UTP can meet this

AES3id or S/PDIF 數位音頻同軸需求 ......

同軸電纜

         1. Distance about 2-3 times that of twisted pairs

         2. Lacks common mode noise rejection of twisted pairs

特定阻抗

         1. 75 ohm required

低電容

         1. <20 pF/ft.

         2. Capacitance controlled by impedance dimensions

         3. Precision video cables suggested

低電阻

         1. Large gage coax such as 20 AWG or 18 AWG suggested

當有類比視頻同軸線需求時 ......

特定阻抗

         1. 75  ohm required

低電容

         1. ~20 pF/ft.

         2. Capacitance controlled by impedance dimensions

         3. Precision video cables suggested

低電阻

         1. Large gage coax such as 20 AWG or 18 AWG suggested

當有 SDI 數位視頻同軸線需求時 ......

阻抗臨界 (Impedance critical)

         1. 75 ohm  +/- 3 ohm

低電容

         1. <20 pF/ft.

         2. Capacitance controlled by impedance dimensions

         3. Precision video cables swept to 400 MHz minimum

低電阻

         1. Large gage coax such as 20 AWG or 18 AWG suggested

Return loss

         1. To be considered

HD-SDI 視頻線纜需求 ......

阻抗臨界 (Impedance critical)

         1. 75 ohm  +/- 3 ohm

低電容

         1. <20 pF/ft.

         2. Capacitance controlled by impedance dimensions

         3. Precision video cables swept to 2.25 GHz minimum

低電阻

         1. Large gage coax such as 20 AWG or 18 AWG suggested

Return loss

         1. >15 dB SMPTE standard to 2.25 GHz

         2. >20 dB suggested to 2.25 GHz