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Re: [TCML] First coil

You use a counterpoise when you can't have an earth ground. It's a substitute for it, and used directly under the coil, and connected as your RF ground. If you were to bury it, then it'd no longer be a counterpoise, it'd just be an earth ground. What I've been told is that the rule of thumb is the radius of counterpoise needs to be at least as big as the distance the largest sparks of your coil can throw. 

https://en.wikipedia.org/wiki/Counterpoise_(ground_system)


On 2017-08-11 07:54, Yurtle Turtle via Tesla wrote:

Does a counterpoise work best directly under the coil, or could it be
buried 10' feet away, but a HUGE welding cable to connect it?

      From: Carl Noggle <cn8@xxxxxxx>
 To: Yurtle Turtle <yurtle_t@xxxxxxxxx>; Tesla Coil Mailing List
<tesla@xxxxxxxxxx>
 Sent: Friday, August 11, 2017 10:50 AM
 Subject: Re: [TCML] First coil

A long wire or rod buried in a horizontal trench often makes a better
ground than a vertical rod, especially when there is caliche or rocks
that prevent digging deep holes.  The good thing about a Tesla coil is
its high impedance, so it can tolerate a high impedance ground.  I have
used a screwdriver pushed into the ground, and it worked well.  You can
pour some water into a depression around the screwdriver.  (Cheesy but
effective)

Safety ground for the power supply should, of course, return to the
service entrance (green wire) and be separate from the secondary low end 
ground.

--- Carl





On 8/11/2017 1:30 AM, Yurtle Turtle via Tesla wrote:

Nice work. Are your ballast laminations individually coated?

        From: Chip Atkinson <chip@xxxxxxxxxx>
  To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
  Sent: Thursday, August 10, 2017 11:59 PM
  Subject: Re: [TCML] First coil
   
Hi Steve,

I put the pictures that you sent up on pupman.com.
http://www.pupman.com/current/swhite/index.html
My fancy thumbnail generating script got lost in the server move a long 
time ago, so it's just file names.

Chip

On Thu, 10 Aug 2017, Steve White wrote:
I just completed my first tesla coil. It is a large one. Here are the prime specs. 

* 8.6" secondary with 1410 turns
* 8 x 10 toroid
* Center line of toroid is 71" above ground plane as defined by javatc * 12-turn primary currently tapped at turn 10.5 ( all primary circuit "wiring" is done with 3/8" copper tubing) * 45 nf of capacitance using 6 Maxwell energy discharge capacitors in a series-parallel configuration with load balancing resistors 
* 10 kva pole pig running at 14,400 volts
* Sophisticated control cabinet including 25-amp variac, ballast, RSG phase control, breakers, contactor, PFC capacitors (currently about 150 uf), volt meters, current meters, EMI filters, MOVs, lockout switches, indicator lamps * Hand-made ballast with adjustable air gap currently set for 20 amps (similar to Richie Burnett's) * Rotary spark gap with one stationary 5/16" tunsten electrode and 4 flying 1/8" tungsten electrodes turning at 3600 RPM * HV leads made from 10,000 volt AC Belden test lead wire threaded through PVC tubing for additional insulation. This is all surrounded by grounded copper braid for uniform field distribution and to protect against streamer strikes.
I made extensive use of javatc to design this coil. I was confident in starting with a large coil because I am a retired electrical engineer thus I had a lot of knowledge about electrical theory. I also own my own mill, lathe, bandsaw, oscilloscope, and signal generator. Finally, I had the funds to muy and/or build quality parts.
Even though this was my first coil, surprisingly it worked the first time that I fired it up. I am currently getting 6.5 foot power arcs. It should be getting up to about 8 feet according to javatc. I am continuing to adjust the primary tuning. I think I need to go a little lower in frequency to account for streamer capacitance.
I do have a few questions concerning RF grounding.  I currently have a copper-clad steel rod driven 3 feet into the ground for the RF ground. This is as deep as I could drive it. I may try a water boring rod to try and get deeper. I currently have the following connected to the RF ground. 

* Strike rail
* RSG motor chassis
* Copper braid shield around HV leads
* Copper braid around RSG power cord
* Pole pig case

Does this sound about right?

Steve White
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