Unidentified Yagi-Uda 17 element 71" boom Big Guy

[samcan]

Who can identify this antenna because i sure can't. From the countless pictures i've compared this too I'm guessing (and hoping) I'm looking at 2.4ghz or possibly a 2.4/5ghz combo. I have measurements in imperial (sorry guys). Looks like the boom is 71 1/4, the driven element is 15" and the first parasitic (which is the smallest) 5 1/16. from the first element to the last (reflector) is right at 65" What do you guys think? I've looked high and low for a formula to calculate the frequency from the measurements to no avail. And the calculators i tried will not let me input the measurements first. Any help is much appreciated. If i'm really lucky and someone enjoys identifying antennas I have another monopole about 2 meters with 4 coils I can post pictures. (possibly a new post?). Thanks in advance I know this is probably cake to most of you but I have very little experience with antenna and anything i've come up with so far is merely a guess.

 

[Les Jones]

As you say the driven element is 15 inches long this is about 1/2 a wavelength of the design frequency. So 15" x 25.4 = 381 mm so a wavelength is 762mm = 0.762 meters.. So the design frequency is 300/0.762 Mhz = 393.7 Mhz. In practice the design frequency will be slightly less than this calculated value as the electrical length of the elements will be a little longer than the physical length. This difference is influenced by the diameter of the material that the elements are made from.
Looking at the picture it does not look like the shortest director which furthest away from the driven element is about one third of the length of the driven element. (As your measurements suggest.) Yagi antennas like this can not be dual band.

Les.

 

[sagor1]

First "parasitic" element is 5-1/16". That is about 13cm. That puts it as a 1/2 wave dipole length for 2.4Ghz (or very close to that). You cannot have a driven element 15" and parasitic elements 5". Does not make sense. I suspect you measured the total circumference of the driven element, which may not be relevant compared to it's end to end length. A folded dipole will be 2 to 3 times longer due to how it wraps around.

 

[unclejed613]

the first director element in front of the driven element looks to be 6-6.5" by comparing to the tape measure... 6.5x2.54=16.51cm that's a wavelength of 33cm which calculates to 909Mhz, which in Region 2 (the Americas) is in an ISM band. this is also amateur radio band, so that's a more likely use for this antenna.

 

[sagor1]

UncleJed is more correct. I forgot to account that 13cm is "half wavelength" based on my calculations. So, wavelength is closer to 25-26cm. That means the antenna is either 903-909Mhz (33cm) or 1.3Ghz (23cm). A more accurate measurements of the first element in front of the driven element would help calculate it better...