Re: Wrong cable... How bad is it?


Jean-Paul
 

Stephen welcoming to the wonderful world of wired transmission of Signals, researched since the earliest days days of Telegraph, telephone and vidéo.

First, câble Zo is important in a matched system eg 50 ohm cal gen and 50 ohm load.
For audio tests with 1 M Ohm , no difference.

As the frequency, and bandwidth go up, and rise times get short, the Zo is more and more critical to obtaining low reflections, as is the cables VSWR, attenuation and phase vs legnth and frequency.

Thus RG174/u is 50 ohm, but dia ~ 3 mm so rather high atten. db/ meter, while RG58/u, is thicker and RG6/u very thick 12 mm so much mess atten per m thoughts all are 50 Ohm.

For use over 20 MHz eg with SG503 or SG504 or fast pulses like PG506, a calibrated special 1/2 m Tektronix cable is preffered . Generally the shorter the cables the better for cal use.
Finally the wire and insulation quality and connectors precision are factors.

We use the Tektronix and Genrad precision cables for critical applications and avoid the cheap, poorly made Chinese clones.

Suggest that you consult the Belden Wire site papers and applications notes, as well as the detailed specifications on whatever cables, connectors and wire you use.

Bon courage

Jon

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