Hi Dan, Try the following code:

CM Inductor Q Calculation
CE
GH 1 500 11.36363636 250 125 125 125 125 5
GW 2 5 125 0 250 0 0 250 5
GW 3 10 0 0 250 0 0 0 5
GW 4 5 0 0 0 125 0 0 5
GS 0 0 0.001000
GE 0
EX 0 3 5 00 1 0
FR 0 3 0 0 3.7 0.1
LD 5 1 1 520 5.7001E7
RP 0 181 1 1000 -90 90 1.00000 1.00000
EN

Note that a detailed description of the "GH" fields are on page 20 of the
"NEC - 2, Part III: User's Guide"; on page 20. The guide can be obtained at
http://www.nec2.org/other/nec2prt3.pdf and is only just over 400 kB.

The coil dimensions you gave me are not physically realizable since 22 turns
of 12 mm diameter wire will result in a coil length of 264 mm. I have
therefore revised the wire radius to 5 mm. NEC will return an error if I
attempt to input a radius of 6 mm.

NEC indicates the coil is 123 uH, and a Q of 4471 at 3.8 MHz. You would
certainly have to silver plate the coil in order to maintain such a Q. The
formation of copper oxide will cause Q degradation over time -- despite what
some people seem to think.

I have thought of building hi-Q inductors with 1/4" copper pipe, but not
sure how you can do the same with 1/2" pipe as it must be very difficult to
bend.

Before building an antenna with such loaded radials I think it would be
interesting to model it with non-loaded radials, and compare it with a
"Lumped element" loading coil analysis.

73,

Frank



"dansawyeror" wrote in message
...
Frank,

I am stuck with the GH descriptor. Do you have a tool that can generate a
description of a coil 250x250 mm with 22 turns of 12 mm tubing?

Is it as simple as doing the division and filling in the entries?

Thanks - Dan

Frank wrote:
"GH" should do it Dan. I also did a Mathcad analysis based on Terman.
If you have Mathcad I can send it to you. One thing I should do is
compare NEC with Terman.

Frank


"dansawyeror" wrote in message
. ..

I am using Reg's programs to calculate the Q and R of 'large'. These
coils are in the range of 220 mm in diameter and long.

There seems to be a difference in the coil simulation between Vertload
and c_poise. In particular c_poise seems more sensitive to coil wire
diameter then vertload. Vertical load will create a coil with low R and a
relativily small wire diameter and pitch, 2 mm and .2 pitch (it does not
predict Q). C_poise requires a large wire diameter, 12 mm and a high
pitch, .8 to achieve similar R values.

Is there a reason for this? Am I missing something?

Is there a way to simulate Q and R for these coils with nec?? How would
one create an nec representation for a coil?

Thanks - Dan - kb0qil