144 Mhz. harmonics rejection stub filter

Filter connected to the output of your transmitter and notch out all the major harmonics.

There are four open-circuit quarter-wave stubs, to notch out the 2nd, 3rd and 4th harmonics.

The 5th-harmonic stub S4 is optional. Leaving it out improves the VSWR from about 1.5 to a near-perfect 50-ohm match.


S1: 0.250 wl at 3f
S2: 0.250 wl at 4f
S3: 0.250 wl at 2f
S4: 0.250 wl at 5f (optional)
T1: 0.265 wl at 1f