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<blockquote data-quote="Frank Koenig" data-source="post: 138578" data-attributes="member: 416">Re: Educate me:&nbsp; AES cablingTo the contrary, it is with short, mismatched lines that we are&nbsp; typically concerned with cable capacitance. This is the &quot;long mic cable&quot;&nbsp; case where the -3dB frequency is 1 / (2 * pi * R * C) where R is the&nbsp; parallel combination of the source and load resistances and C is the&nbsp; total cable capacitance.This is&nbsp; indeed what I was alleging. In a matched-termination transmission line&nbsp; the distributed capacitance is cancelled by the distributed inductance&nbsp; and so the capacitance, in itself, does not matter. As Rob pointed out,&nbsp; the frequency limit for a given length of transmission line is typically&nbsp; governed by loss, which, in other than air- or vacuum-insulated lines,&nbsp; occurs mainly in the dielectric. Another consideration in broadband use&nbsp; might be dispersion, in which different frequencies have different&nbsp; velocities, which smears pulses. I&#039;m not enough of a long distance data&nbsp; transmission guy to know, off hand, under what circumstances this&nbsp; becomes a problem.With respect to what constitutes a &quot;short&quot;&nbsp; line, the lambda/20 figure I gave is conservative and will work in&nbsp; almost all situations -- better safe than sorry. In many circumstances&nbsp; we might get away with using a lambda/4 piece of the &quot;wrong&quot; cable but&nbsp; in RF work lambda/4 is huge. It&#039;s the length of a 1/4 wave antenna, or a&nbsp; 1/4 wave stub, for example.On bandwidth required for binary&nbsp; data transmission, depending on just how the signal is detected at the&nbsp; receiving end, we might want to look at the edge rate (rise and fall&nbsp; times) rather than clock speed. This is true for much of digital&nbsp; hardware design.Hope I&#039;ve managed to communicate, at least a little. --Frank</blockquote>

[QUOTE="Frank Koenig, post: 138578, member: 416"] Re: Educate me: AES cabling To the contrary, it is with short, mismatched lines that we are typically concerned with cable capacitance. This is the "long mic cable" case where the -3dB frequency is 1 / (2 * pi * R * C) where R is the parallel combination of the source and load resistances and C is the total cable capacitance. This is indeed what I was alleging. In a matched-termination transmission line the distributed capacitance is cancelled by the distributed inductance and so the capacitance, in itself, does not matter. As Rob pointed out, the frequency limit for a given length of transmission line is typically governed by loss, which, in other than air- or vacuum-insulated lines, occurs mainly in the dielectric. Another consideration in broadband use might be dispersion, in which different frequencies have different velocities, which smears pulses. I'm not enough of a long distance data transmission guy to know, off hand, under what circumstances this becomes a problem. With respect to what constitutes a "short" line, the lambda/20 figure I gave is conservative and will work in almost all situations -- better safe than sorry. In many circumstances we might get away with using a lambda/4 piece of the "wrong" cable but in RF work lambda/4 is huge. It's the length of a 1/4 wave antenna, or a 1/4 wave stub, for example. On bandwidth required for binary data transmission, depending on just how the signal is detected at the receiving end, we might want to look at the edge rate (rise and fall times) rather than clock speed. This is true for much of digital hardware design. Hope I've managed to communicate, at least a little. --Frank [/QUOTE]

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