[TenTec] Coaxial Ground

[Stuart Rohre]

If you take a coax on a long run to ground from an upper story, its own 
capacitance per foot is going to bypass RF from the inner to the shield.  If 
you connect capacitors across one or both ends, you have added bypassing of 
the RF from inner to the shield.  Unless the coax happens to be an odd 
multiple of a quarter wave line, you simply have both the shield and center 
paralleled and effectively, the RF is on the shield as well as the center 
conductor.

This may appear to improve your grounding, not from the coax "shielding" 
your ground wire, but from the larger diameter of the effective ground being 
the shield along with the center conductor.  The detailed analysis depends 
on the electrical length of the coax, and how far from earth ground, the rig 
happens to be in terms of wavelength fractions.

The capacitance of coax per foot is pretty high, due to the solid 
dielectric; it might be interesting to analyze the same run of coax, if it 
were made of air dielectric coax cable.

Stuart
K5KVH