RG-62 Coax good for a PI ??

[Brian Deese]

I am gathering parts to build several PI machines,is rg-62 good for the coax as it has the lowest capacitance per foot that I have seen. The center conductor is copper plated steel,only problem I know of.May not be a problem?

[WM6]

I am gathering parts to build several PI machines,is rg-62 good for the coax as it has the lowest capacitance per foot that I have seen. The center conductor is copper plated steel,only problem I know of.May not be a problem?

RG-62 is ok.
You can avoid possible mechanical problem due steel rigidity by using some sort of rubber grommet breaking absorber at connection points.

[Davor]

With a given dielectric, every coax with the same impedance will have the same capacity in pF/m. RG-62 is a 93ohm cable, hence it has ~half capacity of a 50ohm cable.

[Brian Deese]

With a given dielectric, every coax with the same impedance will have the same capacity in pF/m. RG-62 is a 93ohm cable, hence it has ~half capacity of a 50ohm cable.

Ok, so I am in need of some education on this topic.How is the ohm rating established,what are the difference between 50,75,93 ohm cables.I may not completely understand impedance,i will read up on it after breakfast.

[Davor]

It is not too complicated if you do not go too deep into transmission lines theory. For all technologies below 1MHz and distances shorter than 1km all these cables present merely lumped element equivalents. In your case ~50pF/m. Higher impedance -> lower pF/m.
You may be able to obtain even somewhat higher impedance coax for AES/EBU applications, but in such case there may be problems with voltage rating. PI Tx may cause arcing.
A somewhat comprehensive and not complicated introduction to transmission lines is found here: http://www.allaboutcircuits.com/vol_2/chpt_14/3.html