Quote:
|
Originally Posted by nomorecomcast
what material/diameter is used for your antenna design? thanks
|
The design can use 300 ohm twin lead for the dipole driven element and 12 or 14 gauge insulated copper wire from Home Depot for the director and reflector, which is why it is called a wire yagi. Or, you can use the copper wire for all three elements.
You can use heavier gauge wire or tubing, but that would be more expensive.
Here are the calculations for the Channel 2 yagi:
Channel 2 Yagi, 57 MHz
5540/57 = 97.19
Reflector 97.19 x 105% = 102.1 inches
Director 97.19 x 95% = 92.3 inches
One wavelength in air is 11810/freq in MHz = 11810/57 = 207.19 inches
DE to Reflector spacing = 0.2 λ = 207.19 x 0.2 = 41.4 inches
DE to Director spacing = 0.15 λ = 207.19 x 0.15 = 31.1 inches
λ (Lambda, Greek) is the symbol for wavelength
Here is a channel 6 yagi for WPVI:
and the calculations for the channel 6 yagi for WPVI:
Channel 6, 82 to 88 MHz, center frequency 85 MHz.
5540/85 = 65.2 inches length for a folded dipole antenna
To convert the dipole antenna into a 3 element beam for more gain, add a reflector and a director:
Reflector is 105% of Driven Element = 65.2 x 1.05 = 68.5 inches
Director is 95% of DE = 65.2 x 0.95 = 61.9 inches
One wavelength in air is 11810/freq in MHz = 11810/85 = 138.9 inches
DE to Reflector spacing = 0.2 λ = 138.9 x 0.2 = 27.8 inches
DE to Director spacing = 0.15 λ = 138.9 x 0.15 = 20.8 inches
Here are some hourglass loops for VHF-Low designed by holl_ands who does antenna computer modeling:
http://imageevent.com/holl_ands/loop...673fd1.eagle_s
for very tall attics