Your first sentence is exactly correct and what I am trying to do. I am using an SWR meter to meaure the the entire system. In other words I was measuring once I had the 50ohm cable connected to the two 75ohm legs, which were then soldered to the DEs of each antenna.
As I mentioned in my first post, the yagis are based on the "Cheap Yagi" design, where the DE is a folded element. The coax is soldered directly to the DE. So in my case, I have two antennas on the same boom. I tested each antenna seperately by temporarily hooking a 50ohm cable to the DE through an SWR meter and measuring. Each antenna was less than 1.5:1.
Then I calculated the length of the two matching sections of 75 ohm coax. I soldered these directly together along with the 50 ohm coax (kind of a home-made T-adapter). Then finally I soldered each of the 75 ohm legs to the DEs. This is the point I measured the SWR and found it 5:1+.
Upon further reading it was suggested to not solder the three coaxes together, but rather to use a T-connector. Also, I read where you include tip-to-tip when calculating length. So in other words if the length comes out to be 4.5 inches for 1/4wave, then that is the total length, including the PL259 connectors end to end. In my case there would only be one PL259 connector per leg and I the other end is soldered directly to the DE.
I have not tried using the T-connector or including the connectors in the overall lengths. So possibly by matching stubs were to long?
Not sure if any of the above makes sense.....any help you could provide would be greatly appreciated.