Removing RF noise from any inverter? how?

Eric, I tried connecting the chassis of the inverter to the chassis of the car and it actually increases the hum.
So, i heard somewhere putting a resistor and capacitor of 47 Microfarads between the chassis of the inverter and the car chassis and the hum diminished to about 5% on the 8022 Khz but is still strong on the 5000 KHz.
Why do you think the capacitor reduces the hum a that frequency?

What's the principle of harmonic behind that hum?

What about if I put a mesh_copper_bread around the cables and instead of connecting it to the earth, I connect it to the earth through a 47 Microfarad cap?
Let me know what you think?
Guy

Thanks Eric.
what you suggest is exactly what I checked out first.
The RF is coming from the case of the inverter and probably from the 12 volts leads.
As I explained in my first post , the battery was NOT connected to my car and the inverter was just OFF with no output leads, 50 metres from my car. As soon as I turned ON the inverter the hum came.
Guy

Bob, thanks for your answer. Before posting I searched the web. I've been successful in reducing the inverter RF interference from 60% to about 5% by using a 47 microfarad capacitor.
During my web search I never found any article which refer directly or indirectly at the usage of a capacitor to reduce an RF hum in the HF band? I would like to know why this capacitior trick is not mentioned and if other tricks also have been ommitted or not mentioned on the web.
What I understand from RF interference: the "hum" at HF 8000KHz is very different from a RF inteference in ELF ( 0.01 KHz to 2 KHz),
VLF, LF produced by the harmonic of a car distributor/generator or main A.C. electrical lines.
Shielding the cabling is one good solution .

Connecting the shielding "directly" to ground is probably not the solution.
I tried and it actually increases the hum noise level.

At 8000 KHz harmonic RF will travel on the outside of any cable including shielding cable.

Connecting the shield to ground via a ceramic capacitor is a more successful in my case because it dimishes the "hum" on the receiver by nearly 50% because I believe there opposition of phase.
Ferrite beads seems to also work but not as well as capacitors. This is the same principle of opposition of phase or phase shift.
Twisting the power cable, like in telephone wires, is good but still not as efficient as a capacitor.

Does anyone know any other technic to reduce RF which are known to work?
Websites? Books?
Practical experience, even if these personal or hearsay experiences sound totally crazy?
Guy