監控視頻線為什么是75歐姆
閱覽次數：3089 次
監控視頻線是(shi)75歐姆的原因：
（1） 75歐姆(mu)，國標名稱是(shi)，包括實心和發泡電(dian)纜(lan)。現在(zai)大家(jia)都(dou)把SYV實心電(dian)纜(lan)叫著視頻(pin)線，把SYWV叫射頻(pin)電(dian)纜(lan)。
（2） 常(chang)用(yong)(yong)的(de)(de)(de)(de)(de)同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)有(you)50和(he)(he)75歐(ou)姆(mu)特(te)(te)性(xing)(xing)(xing)(xing)(xing)阻(zu)(zu)(zu)(zu)抗(kang)兩大(da)(da)類。通信(xin)行(xing)業(ye)(ye)一(yi)(yi)般用(yong)(yong)50歐(ou)姆(mu)，電(dian)(dian)(dian)視行(xing)業(ye)(ye)，安防行(xing)業(ye)(ye)的(de)(de)(de)(de)(de)視頻傳(chuan)(chuan)輸(shu)，都用(yong)(yong)75歐(ou)姆(mu)特(te)(te)性(xing)(xing)(xing)(xing)(xing)阻(zu)(zu)(zu)(zu)抗(kang)的(de)(de)(de)(de)(de)；特(te)(te)性(xing)(xing)(xing)(xing)(xing)阻(zu)(zu)(zu)(zu)抗(kang)是傳(chuan)(chuan)輸(shu)線(xian)的(de)(de)(de)(de)(de)分(fen)(fen)布參(can)數(shu)(shu)，在(zai)電(dian)(dian)(dian)磁場(chang)(chang)(chang)和(he)(he)微(wei)波理(li)(li)論(lun)中(zhong)才好(hao)理(li)(li)解，用(yong)(yong)電(dian)(dian)(dian)工(gong)(gong)、電(dian)(dian)(dian)路(lu)的(de)(de)(de)(de)(de)集中(zhong)參(can)數(shu)(shu)元(yuan)件RLC概(gai)念不(bu)(bu)(bu)(bu)太好(hao)理(li)(li)解。但(dan)可(ke)以(yi)這樣(yang)說，從(cong)(cong)電(dian)(dian)(dian)工(gong)(gong)、電(dian)(dian)(dian)路(lu)角度看(kan)(kan)，同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)就是兩個相互絕緣(yuan)的(de)(de)(de)(de)(de)同(tong)(tong)軸(zhou)導體(ti)，只是結構上和(he)(he)兩根(gen)導線(xian)不(bu)(bu)(bu)(bu)同(tong)(tong)，但(dan)從(cong)(cong)電(dian)(dian)(dian)磁場(chang)(chang)(chang)和(he)(he)微(wei)波角度看(kan)(kan)，它可(ke)以(yi)等效成(cheng)無(wu)數(shu)(shu)多(duo)的(de)(de)(de)(de)(de)微(wei)小(xiao)(xiao)電(dian)(dian)(dian)感，電(dian)(dian)(dian)容，電(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)的(de)(de)(de)(de)(de)有(you)機(ji)組合(he)，分(fen)(fen)析它的(de)(de)(de)(de)(de)傳(chuan)(chuan)輸(shu)特(te)(te)性(xing)(xing)(xing)(xing)(xing)，而且(qie)取得了(le)(le)理(li)(li)論(lun)和(he)(he)實(shi)踐(jian)完全一(yi)(yi)致的(de)(de)(de)(de)(de)結果。這些(xie)(xie)等效成(cheng)無(wu)數(shu)(shu)多(duo)的(de)(de)(de)(de)(de)微(wei)小(xiao)(xiao)電(dian)(dian)(dian)感，電(dian)(dian)(dian)容，電(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)，都是“分(fen)(fen)布參(can)數(shu)(shu)”，是從(cong)(cong)電(dian)(dian)(dian)磁場(chang)(chang)(chang)角度看(kan)(kan)它對(dui)信(xin)號(hao)的(de)(de)(de)(de)(de)影響和(he)(he)作(zuo)(zuo)用(yong)(yong)，形式上看(kan)(kan)不(bu)(bu)(bu)(bu)見模不(bu)(bu)(bu)(bu)著，一(yi)(yi)般儀表也測不(bu)(bu)(bu)(bu)出來，但(dan)卻(que)是客(ke)觀存在(zai)，對(dui)傳(chuan)(chuan)輸(shu)信(xin)號(hao)有(you)實(shi)實(shi)在(zai)在(zai)影響的(de)(de)(de)(de)(de)“參(can)數(shu)(shu)”，對(dui)高頻信(xin)號(hao)來說，電(dian)(dian)(dian)纜(lan)的(de)(de)(de)(de)(de)這些(xie)(xie)分(fen)(fen)布參(can)數(shu)(shu)電(dian)(dian)(dian)路(lu)，最(zui)后可(ke)以(yi)等效成(cheng)75歐(ou)姆(mu)的(de)(de)(de)(de)(de)阻(zu)(zu)(zu)(zu)抗(kang)，這個阻(zu)(zu)(zu)(zu)抗(kang)，是一(yi)(yi)種等效特(te)(te)性(xing)(xing)(xing)(xing)(xing)效果并不(bu)(bu)(bu)(bu)是一(yi)(yi)個有(you)形電(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)，所以(yi)叫“特(te)(te)性(xing)(xing)(xing)(xing)(xing)阻(zu)(zu)(zu)(zu)抗(kang)”。同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)內(nei)外(wai)導體(ti)的(de)(de)(de)(de)(de)直徑，絕緣(yuan)介質(zhi)介電(dian)(dian)(dian)常(chang)數(shu)(shu)不(bu)(bu)(bu)(bu)同(tong)(tong)，可(ke)以(yi)表現為不(bu)(bu)(bu)(bu)同(tong)(tong)大(da)(da)小(xiao)(xiao)的(de)(de)(de)(de)(de)特(te)(te)性(xing)(xing)(xing)(xing)(xing)阻(zu)(zu)(zu)(zu)抗(kang)，可(ke)以(yi)大(da)(da)也可(ke)以(yi)小(xiao)(xiao)，但(dan)傳(chuan)(chuan)輸(shu)線(xian)阻(zu)(zu)(zu)(zu)抗(kang)不(bu)(bu)(bu)(bu)同(tong)(tong)時(shi)，會產生(sheng)反射(she)信(xin)號(hao)，把特(te)(te)性(xing)(xing)(xing)(xing)(xing)阻(zu)(zu)(zu)(zu)抗(kang)設定(ding)為75歐(ou)姆(mu)，估(gu)計是一(yi)(yi)種“標準(zhun)化”的(de)(de)(de)(de)(de)結果。總(zong)之(zhi)，分(fen)(fen)布參(can)數(shu)(shu)，特(te)(te)性(xing)(xing)(xing)(xing)(xing)阻(zu)(zu)(zu)(zu)抗(kang)，匹配反射(she)等概(gai)念，用(yong)(yong)電(dian)(dian)(dian)工(gong)(gong)電(dian)(dian)(dian)路(lu)理(li)(li)論(lun)和(he)(he)概(gai)念不(bu)(bu)(bu)(bu)太好(hao)理(li)(li)解；記得一(yi)(yi)篇文章里(li)在(zai)分(fen)(fen)析雙絞(jiao)(jiao)線(xian)和(he)(he)同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)傳(chuan)(chuan)輸(shu)時(shi)，用(yong)(yong)了(le)(le)他(ta)實(shi)測的(de)(de)(de)(de)(de)一(yi)(yi)個每米有(you)**Pf電(dian)(dian)(dian)容的(de)(de)(de)(de)(de)數(shu)(shu)據，同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)容大(da)(da)，雙絞(jiao)(jiao)線(xian)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)容少，用(yong)(yong)來說明(ming)的(de)(de)(de)(de)(de)傳(chuan)(chuan)輸(shu)特(te)(te)性(xing)(xing)(xing)(xing)(xing)“優(you)于”同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)；但(dan)實(shi)際傳(chuan)(chuan)輸(shu)特(te)(te)性(xing)(xing)(xing)(xing)(xing)卻(que)剛好(hao)相反，暴(bao)露(lu)了(le)(le)作(zuo)(zuo)者(zhe)是根(gen)本不(bu)(bu)(bu)(bu)懂電(dian)(dian)(dian)磁場(chang)(chang)(chang)原理(li)(li)的(de)(de)(de)(de)(de)。工(gong)(gong)程中(zhong)常(chang)見的(de)(de)(de)(de)(de)同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)“焊(han)接”“扭(niu)接”方法，從(cong)(cong)電(dian)(dian)(dian)工(gong)(gong)、電(dian)(dian)(dian)路(lu)的(de)(de)(de)(de)(de)角度看(kan)(kan)，是“對(dui)的(de)(de)(de)(de)(de)”，但(dan)它破壞了(le)(le)同(tong)(tong)軸(zhou)電(dian)(dian)(dian)纜(lan)的(de)(de)(de)(de)(de)同(tong)(tong)軸(zhou)性(xing)(xing)(xing)(xing)(xing)和(he)(he)特(te)(te)性(xing)(xing)(xing)(xing)(xing)，形成(cheng)了(le)(le)阻(zu)(zu)(zu)(zu)抗(kang)不(bu)(bu)(bu)(bu)連(lian)續(xu)點，產生(sheng)反射(she)，也是這個道理(li)(li)；
編輯：夏 江
| 
中文版
