Vor balun design choice

[5469]

Hello,

I am replacing my old vor antenna, and the old coax cable. I have new RG400 coax and accesories. I got a used antenna from a parted out acf, tested and certified.

For the balun, I know how to build one following AC 43.13-2B. And also I can build Pawsey Stub design.
Calculation for the central VOR frequency gives me 112.975 MHz. Average between 108 and 117.95
Wavelength for that frequency is 2.65 meters and quarter wave is 66 centimeters or 26.3 Inches.

Now, two questions:

Q1 Calculating with a velocity factor of 0.70 gives a balun about 16 inches. AC 43.13-2B makes no mention of using the velocity factor though.
With VF = 1 length gives 26 inches.

I welcome your advice about this. What is a best design 16 or 26 inch ? I think the second is best, but not sure.

Q2. Has someone experience using Pawsey Stub design ? I think that Cessna used AC 43.13-2B design for decades and they had good reasons.
Pros and Cons between both designs ?

Thanks, and kind regards.

[3510]

My opinion is that you should not consider the VF of the coax. Only the outer shield of the coax is used to form the 1/4 wave stub. Therefore, the 26 inches should be used as specified in the design.
Regards, Tom