AIM 914 produces internally inconsistent results



A new release, AIM914 appeared recently.

In the common theme of one step forward, two steps backwards, this version has defects that were not present in AIM910B.

Let's review the internal consistency of this part of the display screen.

Most of the values given above are calculated from a single measurement value, and should be internally consistent. That measurement value is translated to different quantities, many based on the stated Zref (75Ω in this case).

Let's assume that the values given for Rs and Xs are the basis for the other quantities, and check the consistency of those other values with Rs, Xs based on Zref=75Ω as shown.

Above are various values calculated from Rs=12.428Ω, Xs=17.173Ω and Zref=75+j0Ω.

Working down from the top of the AIM results:

  • SWR (4.596) is wrong, it should be 6.36;
  • Rho Mag (0.6426) is wrong, it should be 0.7282;
  • s11 (-0.6530+j0.3251) is ok;
  • % refl power (41.3) is wrong, it should be 53.0;
  • Return Loss (3.84dB) is wrong, it should be 2.75dB; and
  • Cable Loss (1.92dB) is wrong, it should be 1.38dB.

Does not inspire a lot of confidence, does it?