"SWR of 1.9-2.1:1 and impedance of around 150 ohms........"
"Hmm, With the impedance that you give, you should show an SWR of 3:1."
not if reactance is present........your statement would only apply when dealing with a purely resistive, non reactive load.
....Z (impedance) is equal to the square root of the sum of R (resistance) squared and X (reactance) squared. impedance is a complex conjugate of both reactance and resistance.
VSWR = 1:1 when R = 50 and X = 0.
an undetermined value of X (reactance) and R (resistance) of other than 50 ohms is offsetting the VSWR.
VSWR can only be directly proportional to Z when Z = R and X = 0.
2 ohms of R (resistance) and 100 ohms of X (reactance) would provide a vswr indication of between 1.9 - 2.1 with Z = 100 ohms.
Z = sqrt (R^2 + X^2)
Z = sqrt (2^2 + 100^2)
Z = sqrt (4 + 10000)
Z = sqrt (10004)
Z = 100.019 ohms Z (impedance)
112 ohms of R (resistance) and 100 ohms of X (reactance) would provide a vswr indication of approximately 3:1 with Z = 150 ohms.
Z = sqrt (R^2 + X^2)
Z = sqrt (112^2 + 100^2)
Z = sqrt (12544 + 10000)
Z = sqrt (22544)
Z = 150.146 ohms Z (impedance)
the value selected for X was done randomly for purpose of example, your values may differ. any time X = something other than 0 then VSWR is not directly proportional to and is no exacting indicator of Z (impedance) match/mismatch.
Z (impedance) is only altered when adjusting the stinger or whatever because X (reactance) and R (resistance) is what is actually being adjusted. as the value of X or R is varied, so is the impedance (Z).
Z = sqrt (R^2 + X^2)
