Total posts : 45366
1. If you’re running 6-7 watts, you shouldn’t have to worry about a bit more coax loss from a stub filter (and the extra line from filter to transmitter). I thought you were running a watt or less.
2. Regarding the LP filter in Figure 5:
a. I don’t know what the proper L & C values would be for VHF.
b. Since your primary concern is second harmonic suppression, I think the coax stub would still be easier to do. The length formula is shown below Figure 6. You should be able to find the velocity factor for your coax online. Plug in 107.9 MHz to get your stub length, then use half that length for the coax between the stub and the transmitter. If you’re using scrap coax and have to guess the velocity factor, I’d use 0.66 for solid plastic center insulation and 0.8 for foam center insulation.