So here's that new video I promised about measuring the various antennas. The VSWR is a complicated measurement for sure, but a few basics are:
1) Most manufacturers pass or fail their products compared to a baseline VSWR measurement of >2. Meaning if it is higher than 2 across the frequencies it is intended to work in, it will fail and be rejected.
2) A VSWR of 1 is perfect and never achieved in the real world.
3) VSWR is logarithmic. A VSWR of 2 represents a loss of 10% of the transmit power. A VSWR of 3 represents a loss of 25% of the transmit power. Example: If you have a 100mW transmitter (like the P3A/P4), using an antenna with a VSWR of 3 for the channel you're operating on, can only output 75mW.