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Re: [TCML] secondary connections & RF ground

Hi Matthew,

Thanks for your help.  Below is my original email.  

The second photo shows the connection between the secondary and top load toroid.  You can see that the boys put the connection beyond the plastic flange, where they found an existing hole.  By "very close to the cylinder of the secondary" I meant, does the connection need to be as close as possible to the secondary's pipe?  I'm not sure if the field strength is greatly improved there, how quickly that field might drop off, or if it even matters.

We tested the spade lug ground connection to the secondary yesterday.  That 12AWG wire goes to a barrier strip, then through 4AWG cable, which is soldered to a 2' length of rebar pounded into the ground.

Thanks again.


On Jun 14, 2012, at 12:05 PM, Matthew Edwards wrote:

I realize that your photographs were deleted but they might be helpful. Maybe you could post to Flickr or similar account?

I am still a rook but here is my best understanding of your situation.

For the arcing between the primary and secondary, you will probably need to adjust the spacing. It is probably a coupling issue. I'd start with about 1" between the two, and perhaps adjust the secondary so that the first turn of wire is near the height of the primary. It may be helpful to enter your measurements into Javatc and tweak them a bit until things look good. Then physically adjust the coil.

The method you described for connecting the bottom of the secondary to a lug has worked for me in the past, just make sure the connection is tight (solder is a plus).

As far as the toroid connection, I'd need to see a photo to understand what you mean by "near the cylinder of the secondary". I generally keep the windings tight with a strait connection to a threaded brass stud. I have seen people wrap a few loose turns near the top but have no idea of the benefits or losses of doing such.

Hope this helps!
Good luck

Matthew Edwards


Hi Folks,

My son and his friend have finished building their coil, and are troubleshooting.  They have been having problems with arcing between the primary and secondary.  I read yesterday that the secondary should be grounded, so they fixed that but have yet to test it again.

Our questions: 

1. what is the best way to ground the secondary?  I have seen a couple of articles about using a strip of copper.  Will a simple soldered space lug connector plugged in to another spade lug connector soldered to 12AWG wire work?  That 12AWG wire then goes to a barrier strip, which goes to ground.

2. how critical is it that the connection to the toroid be very close to the cylinder of the secondary?  should there be a few looser windings gradually ascending to the connection?  
here is theirs:

3. how thorough should we be with RF ground?  right now we have a few 2' pieces of rebar pounded almost all the way into the ground, with ground wires wrapping the rebar.  they have also experimented with running some garden fence under the coil, also connected to the rebar.  the best level ground is in the driveway, but is it better to be on the lawn?

Great fun.  Thank you all for your help! 

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