This is the way a linked dipole work. The 20m configuration is 32 feet long (16 on each side) and you simply double those numbers for 40m. So for the 40m section, you actually add only the difference with the already 16 feet you have for 20m coverage. You can go on this site ( http://www.saarsham.net/coax.html ) and cut your antenna exactly at the frequency you target. Mine is set for 14.061 and 7.031 Mhz. With the internal ATU of my Elecraft KX3, I got 1:1 SWR on both band! Finally, Add 15 feet of paracord on each side to fix each leg about 5 feet high and you get a classic inverted V dipole ready to get on the air!