RadioBanter - View Single Post - From NEC2 to the real world with accuracy

Richard Clark · March 12th 08, 08:35 AM posted to rec.radio.amateur.antenna

On Tue, 11 Mar 2008 22:47:57 -0700 (PDT), wrote:

So my question is, what is the most accurate way to make sure when I
build the quad that I account for the velocity factor (unknown) of the
wire I use? Should I grid dip the elements and make sure they agree
with my NEC2 model?

Hi Scott,

This sounds like a good solution, but you don't state the limits of
accuracy you've painfully sought to achieve. I'm not sure about the
reference to a million iterations (which would certainly suggest the
erosion of accuracy through accumulating rounding errors).

However, GDOs don't suggest precision to me. Yes, you can measure the
frequency to a jillion places, but can you find the null to the same
resolution? Meters are not all that resolving unless you've got them
in a bridge.

Can I build a simple loop on a higher frequency
with the wire and then somehow use that information to rescale my wire
lengths?

Sure, but you seem to inform yourself about the difficulty with the
prescient questions that follow:

What is the "right" way to do this? I wonder how consistent
velocity factor will be if I do my own coating on the wire....maybe
hand coating is a bad idea for this reason....

I would first ask why you are coating them at all?.

If I might anticipate because the copper oxidizes and presents a high
resistance to current, I would point out that enamel is even more
resistive and the current isn't going to travel through it either (the
current will travel through the proverbial path of least resistance -
under the coating of resistive layer covering no matter what it is
composed of).

73's
Richard Clark, KB7QHC