Thursday, June 27, 2013

HF Loop Options

I used the 4nec2 program to lay out and briefly analyze my options for setting up an HF loop antenna using the 4 trees I selected to suspend the loop over the back yard. The graphic here shows 2 options for a loop supported by the 4 trees (green discs). The outer perimeter, with dimensions (in feet) marked in red, totals 421 ft, and reaches every tree, and would be appropriate for coverage starting at 2.39 MHz. The height above ground would be about 25 ft.

The inner square, with dimensions in blue, shows a loop designed for about 3.7 MHz, totaling 272 ft.  The 4 line segments with green dimensions represent the ropes that would be needed to support the smaller loop from the same 4 trees. A convenient feed point, close to one end of my house, is near the lower right corner. In the antenna model this is represented by the pink circle. The house would be located partly beneath the 89 ft segment of the larger loop.

The far field radiation patterns for the two loops are somewhat similar, with 80 and 40 m producing one or two lobes with high angle of radiation. The higher bands yield lower angles of radiation, but with multiple lobes. On the 10 m band, the larger loop produces 14 lobes, and the smaller loop produces 12 lobes.

Now that I have a scale drawing saved as a NEC file, I'll explore some other alternatives (triangles?, dipoles?) before hanging wire.

John

Update:  I put up the smaller loop diagrammed above -- 68 ft on each side.

Friday, June 21, 2013

EasyBCD vs GRUB2

I learned about EasyBCD while reading some replies in this Google+ posting:
https://plus.google.com/111420842954473821448/posts/FHDERi6UCii


I thought about using EasyBCD on my Win7 laptop where I recently installed Ubuntu 13.04. The GRUB2 menu had Ubuntu as the default boot choice and 3 appearances of Win7, of which two were restore or recovery options. I was not sure I wanted to edit the GRUB2 menu. Then I also stumbled upon this forum posting by the user who ended up with tandem bootloaders:
http://ubuntuforums.org/showthread.php?t=2126946

Then I decided to stick with editing the GRUB2 menu. I found this solution to make it easier and was pleased with the results:
http://www.howtogeek.com/howto/43471/how-to-configure-the-linux-grub2-boot-menu-the-easy-way/

John