Gearslutz.com - View Single Post

collo · 10th December 2009

This thread is to allow discussion of a proposed change in the way inverse panels are calculated in the QRDude calculator.

The hoped-for contributors would be those who have already helped with the development so far, namely TerryJ, Lupo and Xenon. All others are welcome, of course.

...........................

An inverse QRD panel is one where the well depths are the opposite to the normal panel.

For a 1D N7 normal. panel, the depths range from 0 to 6 depth units.
For a 1D N7 inverse panel, the depths range from 7 to 1 depth units.

The amount of phase shift introduced by a given well is equal to 360 degrees minus that introduced by the same well position in the normal panel.

When QRDude was first being developed, it was proposed that the deepest well in the inverse panel, which produces 360 degrees phase shift, could be replaced by a zero depth well. At the time there was not enough known by our little group to say with certainty that it was allowable. The calculator was thus produced without this being included.

Since then, 2D panels have been added to the mix, and in researching these, an example of a this substitution has come to light. By none other than the most reputable producer of panels.

...........................

Here is a screenshot showing grab from the QRD overview notes for the calculator along with the product in question - a 2D inverse N7 panel...

Here is the same panel as produced by the current version of QRDude. The difference can be seen at the bottom left corner...

I think it is well worth looking a this again. The benefits in allowing the substitution are a shallower inverse panel and simpified treatment of 2D inverse panels. (Fairly large changes to the code needed, but in the end, a better product)

As a means of investigating this a little more, here is a drawing that will eventually end up in the guide.

The standard equation for determining the well depths of a QRD panel is:
Well depth = (well position squared) mod N .... where N is the number of wells.

The green area shows the depths for a normal N7 panel if the mod part of the equation was not present. The dark horizontal lines show depths which are multiples of one wavelengths worth of shift.
The blue vertical arrows show how the mod operator removes these multiples to give the familiar N7 pattern (shown in grey)

This same approach when applied to an inverse panel would produce the transform we see in the commercial 2D inverse panel shown earlier.

I would like to canvas opinions on this before taking it any further...

10th December 2009	#1
collo Gear maniac Join Date: Aug 2009 Location: Newcastle, Australia Posts: 247 Thread Starter	QRDude design change disccussion This thread is to allow discussion of a proposed change in the way inverse panels are calculated in the QRDude calculator. The hoped-for contributors would be those who have already helped with the development so far, namely TerryJ, Lupo and Xenon. All others are welcome, of course. ........................... An inverse QRD panel is one where the well depths are the opposite to the normal panel. For a 1D N7 normal. panel, the depths range from 0 to 6 depth units. For a 1D N7 inverse panel, the depths range from 7 to 1 depth units. The amount of phase shift introduced by a given well is equal to 360 degrees minus that introduced by the same well position in the normal panel. When QRDude was first being developed, it was proposed that the deepest well in the inverse panel, which produces 360 degrees phase shift, could be replaced by a zero depth well. At the time there was not enough known by our little group to say with certainty that it was allowable. The calculator was thus produced without this being included. Since then, 2D panels have been added to the mix, and in researching these, an example of a this substitution has come to light. By none other than the most reputable producer of panels. ........................... Here is a screenshot showing grab from the QRD overview notes for the calculator along with the product in question - a 2D inverse N7 panel... Here is the same panel as produced by the current version of QRDude. The difference can be seen at the bottom left corner... I think it is well worth looking a this again. The benefits in allowing the substitution are a shallower inverse panel and simpified treatment of 2D inverse panels. (Fairly large changes to the code needed, but in the end, a better product) As a means of investigating this a little more, here is a drawing that will eventually end up in the guide. The standard equation for determining the well depths of a QRD panel is: Well depth = (well position squared) mod N .... where N is the number of wells. The green area shows the depths for a normal N7 panel if the mod part of the equation was not present. The dark horizontal lines show depths which are multiples of one wavelengths worth of shift. The blue vertical arrows show how the mod operator removes these multiples to give the familiar N7 pattern (shown in grey) This same approach when applied to an inverse panel would produce the transform we see in the commercial 2D inverse panel shown earlier. I would like to canvas opinions on this before taking it any further...