RF Ground system
The Radio Frequency ground system is needed for coils that are above the bare minimun low power coil. Depending on how much power you are going to pump through the coil sets the scene for how good an RF ground will be needed. For low to medium powerd systems, a single rod of about 5' to 8' long is suitable. If you get into higher powers, a good copper clad or solid copper rod 8' long is a better choice. Multiple rod systems are used for high powered systems like Pole Pigs. With the multiple rod systems, you will need to connect the rods to each other to increase the grounding ability ( and it makes sence to do that anyway cuz there is no sence in leaving a perfectly good rod in the ground and not having it attached to anything :) . The most affordable and effective way to connect the rods together is to use a #4 solid copper wire. If you can find copper strap, even better.
But alas... not all of us have access to a chunk of ground in which
we can drive a rod into. So.... there are options, not the best,
but they are options. Option # 1... use an existing ground rod that
is normally attached to the circuit box. Option # 2... use a water
supply pipe ( best is the one that feeds into the house/dwelling , it has
to be metal ... not PVC) Option # 3 ... any well grounded
metal object sunk into the earth by at least 2 - 3 feet. ( not the best
choice ) .
Okay.... now where does this RF ground hook to ?? It is connected
to the base of the secondary coil, the ground of the transformer(s), and
the strike ring. If you run a medium to high powered coil without an RF
ground.... strange things happen.... the coil will spark
all up and down the secondary ( not good) the voltages produced by the
primary/secondary can work their way back to the transformer and back into
the supply voltage. Ever see a wall socket shoot out blue sparks 8" long?
RF Ground attached to bottom of secondary
coil