This Spartan 172040 (Tribander) has been designed for the bottom of the sun-spot cycle and also to act as a simple 2-element monobander yagi on 17M, 20M & 40M. This design was accomplished by interlacing a 2-el-20 & 2-el-17 on to the same boom as the JK402.
Here are the important features ....
1. The feed point for 17M, 20M & 40M are connected using a transmission line, the same way as the JK-MidTri & JK-BigTri.
2. The mast mount position is right at the center of the antenna at 108".
3. All the 3 bands are connected with a single-feed (50-ohms)
4. The overall gain and swr on all bands is consistent & provides excellent performance.