# Re: [TCML] JAVATC - questions

```Hi Dennis,

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Regarding the input for Primary Radius 2 (for a flat spiral primary),?do you enter the full radius (i.e., 1/2 the full diameter) of the primary...or some other number?? The reason I ask is,?the program Output Data shows Average Space Between Turns around 0.5".? I know my actual spacing isn't perfect, but it's not that far off.? I've gone back to measure with a ruler?& spacing is generally very close to 0.25" edge-to-edge.? Seems like the program is giving me center-to-center spacing,?or I'm?just entering something wrong.?
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The program output for average spacing is edge to edge. For a flat coil, radius 1 represents 1/2 of the inner diameter. Radius 2 represents 1/2 of the outer diameter. For example, an inner radius of 4" and an outer radius of 8" using 8 turns of 0.25" tubing will result in an output average spacing of 0.25" edge to edge. I think your entering something incorrectly.
```This?problem may be due to my not properly interpreting?the explanation diagram's R1/R2 terminology.? I could use clarification on this.
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This may be my fault. The diagram shows R1/R2 for the flat coil case. This isn't a division but meant that either R1 "or" R2 can be used for inner or outer radius inputs. The reason is that some people wind flat secondary coils and may connect ground on the inside or outside. Because Javatc assumes radius 1 is the grounded end, you need to insert radius 1 as the actual grounded end (so in these flat coils where the rim is grounded, we would insert the large outer radius into radius 1 and the smaller into radius 2. That diagram can be confusing and certainly needs updating. The diagram is used for both secondary and primary inputs.
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For a standard flat primary, simply use radius 1 for the inside and radius 2 for the outside.
```Also,?the program sometimes changes the?value for Primary Radius 2?from what I had input.? I don't know why it does this or whether it means I'm doing something incorrectly.
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You are allowing Javatc to tune your coil (the checkbox is checked). When you allow Javatc to tune your coil, Javatc is basically moving the tap point for you, from the outer most edge inward (or outward) until the coil is in tune. It does this by unwinding the outer section (thus a new radius 2 is inserted into the box) and evaluating the inductance. If the tune point requires "less turns", radius 2 and the turns will decrease. If the tune is point requires "more turns", radius 2 and the turns will increase.
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In the same respect, if you insert a desired coupling value, Javatc will physically move the primary up or down as needed. In that case, both the heights inputs will reflect new values.
```Last question, the explanation text for primary inputs refers to connecting the the flat spiral primary to ground.? In my case, the primary is not connected to ground.? Rather, the end of the inside turn is connected to the tank cap and the other connection is the primary tap from the spark gap.? No primary coil connections to ground.? Will the program still work for this configuration?
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Yes. The text is meant for secondary coils. Both the secondary and primary use the same help files. I should have clarified that batter in the pic. Most primary coils using NST's are not connected to ground. Other transformers allow for a grounded inner primary turn. In either case, don't worry about it. For the primary, inductance is the same regardless (uses low frequency inductance). If it was a flat secondary coil, then there would be a difference in the high frequency inductance depending on which end is grounded which is where the secondary frequency is derived.
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Take care,
Bart

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