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Cable resistance and VGA cable chaining

Kyanzes

Kyanzes

Golden Member

My question is two-fold:

1., When it's indicated on cable that it has, say, 75 Ohm of resistance, is that for the whole cable or for a certain length of it? e.g. 75 Ohm / meters (so, in that case, a 1.5m cable would have 112.5 Ohm of resistance... ???)

2., Can I simply string VGA cables from my pc to my TV using 1.5m standard extenders?

Thanks in advance!

 
No, 75 Ohm is the impedance (sort of the "AC resistance" )which mainly depends on the ratio of inductance of capacitance per unit length ( sqrt(L/C) ), which in turn depends on the geometry of the cable.
Hence, impedance is property of the cable as such and does not depend on the length, a cable with 75 Ohm impedance can have zero resistance.

The maximum length of the cable will depends on several things, but primarily on the losses in the cable (which DO depend on the resistance).
There is no way to predict whether or not it will work without knowing more about which cable you are using etc (usually specificed as dB/ft) .





 
From what i can find a good quality VGA cable can be as long as 20 meters without signal issues and without the need for a signal amp. Granted it needs to be a top quality cable and a single cable. Using multiple cables could add to the signal drop.
 
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