In article , Chel van Gennip wrote:
On Fri, 16 Dec 2005 19:21:44 +0100, Mannr wrote:

I have received cheap cable from companies like MCM or Parts Express,
or maybe even All, where instead of good cable with less than 30-40 pF
per foot, had over 100 pF per foot, which are pretty poor. Never know
until you measure them. Its not likely to create a problem with short
cables though. Never know what the DA is with some of them.

greg

Does anyone ever cut/dissassemble these cables? I have. Many, if not
most of the cheap cables are not shielded at all! By shielded I mean
there is an insulated inner wire and an outer stipped wire, braided or
twisted around it.

What I'd like to know if is there is a way to test this, without cutting
the cable.

I think a 75 Ohm coax is no rocket science. 75 Ohm cables for sattelite
will transfer signals up to 2 GHz over quite long distances, 75 Ohm cables
for cable TV will do the same for frequencies up to 1 GHz, 75 Ohm cables
for camcorders will do that up to 5 MHz. All those cables go for about
0.30 per meter in bulk. Where is the monstrous magic you need to transfer
a 20KHz (50KHz???) audio signal?

You find some specifications for standard wires at:
http://www.rfcafe.com/references/ele...coax_chart.htm

Its all about drive impedance. Many consumer devices have 500-1000 ohm
driving impedance. A 100 foot el-cheapo cable might have 6 dB loss at 20kHz.
Not that many people use 100 foot cables!

greg