On 3/18/13 6:36 AM, w5als wrote:
(the same is true for a vertical antenna. Radials beat a ground rod every which way. ) the radials and a counter poise is use to reflect signal (not ground) try what the other person said chicken wire and see if if work if it doesn't try something else. I have more equipment in my shop than you have in a home, and my 6in Tesla coil had effect on nothing. now would I do that ever day no, to me there is nothing better than earth ground to dissipating RF. Somebody said running a 100 ft wire to ground make a antenna, what is the chicken doing if it does not go to earth ground. the coil will work right but the RF is going to dissipating in all directions and to me that not good.
You're not trying to dissipate anything.. What you're trying to do is provide short path for the current.
The smaller the area of the loop, the smaller the radiated field. With a discharge "into air" it's a bit tricky to figure out where the current is flowing, but it's mostly capacitively coupled to the surroundings.
What the chicken wire does is provide a wide area low resistance "plate" for that capacitor (the other electrode is the spark or topload). This makes most of the current flow in the chicken wire (it's low resistance) as opposed to in other conductors that may be in the vicinity (sprinkler valve wires, phone lines, etc.).
The other positive effect of the chicken wire is that it's a pretty effective electrostatic shield. That is, the fields on the "other side" of the chicken wire are fairly uniform, and uniform fields tend not to cause current flow. Current flow is what radiates or induces voltages.
I believe it was Jochen Kronjaeger who showed a nice example of running a big coil in a small room with a semiconductive sheet hanging from the ceiling.
The problem with electrostatic shields is that while very effective for radiated E-fields (the VHF and impulse transients), they aren't very good for magnetic fields. For most TCs at the fundamental operating frequency the magnetic field is MUCH larger than the E-field (in terms of energy stored in it). You're very much in the "near field" of the device (when the wavelength is 3000 meters), so the usual E/H = 377 doesn't apply.
On the other hand, I think most of the "interference" from tesla coils is not the 100kHz fundamental, but is the transients from the sparks. The top load of a few tens of pF at a few hundred kV discharging through a spark in a few nanoseconds is a huge di/dt, and the loop is large.
Since the radiated field is proportional to di/dt and loop area, you're in a tough spot both ways.
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