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On Aug 15, 7:09?am, "amdx" wrote:
Is it possible for a VSWR meter to read 1 to 1 with reactance at the antenna? Ex. If the antenna Z was R= 30 and X= 40 would the meter read 1 to 1? Or is there a combination of R and X that would give 1 to 1? Thanks for your answer and explanations, Mike As others have pointed out, unless the line is lossy, the answer is no. Here is a way to calculate SWR from R and X without the complex arithmetic. It is taken from 'Reflections: transmission lines and antennas' by Walt Maxwell, 1st ed, page 23-5, or 2nd ed page 'appendix 3-1'. Let r = R / line impedance Let x = X / line impedance b = (1 + r*r + x*x) / r SWR = (b + SQRT(b*b - 4)) / 2 The minimum value of b is 2 when r = 1 and x = 0 The minimum value of SWR is 1 when b = 2 Hence it can be readily seen that any reactance will cause the the SWR to be greater than 1 at the load.. Just to complete the maths,the modulus of the relection coefficient, ie mod(p), = SQRT( (b-2) / (b+2) ) HTH and 73 John KC0G |
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