The general formula for a loop is 1005/F(MHz). Loops are designed for the lowest frequency of operation and then provide even and odd harmonic operation from there. When using transmission line for matching it will normally be designed to operate on the design frequency.
Using 26.965 MHz for channel 1 the formula is 1005/26.965 = about 37 ft, 3.25". That is for bare copper wire. It will be about 5% less when using insulated wire. A VSWR meter/bridge or an antenna analyzer is helpful for fine tuning at this point. (Note: Use a different frequency if operating elsewhere of course. I'm using 26.965 which is the normal CB Channel 1 frequency for these examples.)
The general size for different geometric shapes are:
Delta (3 sides): 12' 5" per side, about 10' 9" in height for vertical.
Sqr (4 sides): 9' 4" per side, about 13' 2" diagonal
Hex (6 sides): 6' 2.5" per side, about 12'8" diagonal
Oct (8 sides): 4' 8" per side, about 12' 2" diagonal
The 75 ohm cable is 246/F(MHz) x Velocity Factor (VF) of the cable used.
The cable is usually RG-59/U or RG-6/U. The VF for RG-59/U is usually .82 (82%), and for RG-6/U it is usually .81 (81%).
The cable length is then (246/26.965) x .66 for RG59/U = 9.12 x .66 = 6.02 ft or (246/26.965) x .81 for RG-6/U cable 9.12 x .81 = 7.38 ft.
This should get you in the ballpark.
73,
Mike
