AIM 916 produces internally inconsistent results



AIM915a was recently pulled from the distribution site and replaced by a new release, AIM916.

AIM916 chokes on some calibration files created with earlier versions, so again historical scan data is rendered worthless. Note the illogical diagnostic message… typical AIM quality.

I cannot recall ever finding a new release that did not have significant defects, commonly inconsistency between displayed values. In the common theme of one step forward, two steps backwards, this version has defects that were not present in AIM910B.

This problem existed in AIM915a, it persists in AIM916.

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 (50Ω 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=50Ω as shown.

Above are various values calculated from Rs=49.720Ω, Xs=0.090Ω and Zref=50+j0Ω.

Working down from the top of the AIM results:

  • SWR (1.508) is wrong, it should be 1.01;
  • Rho Mag (0.2027) is wrong, it should be 0.002949;
  • s11 (-0.0028+j0.0009) is ok;
  • % refl power (4.1) is wrong, it should be 0.00087;
  • Return Loss (13.86dB) is wrong, it should be 50.61B; and
  • Cable Loss (6.93dB) is wrong, it should be 25.30dB.

What was fixed in AIM916? Well, that seems to be a secret… but some stuff that worked was broken (the cal file issue) and some stuff that was broken remains broken.

Does not inspire a lot of confidence, does it?

Will this internal error that has been in many released versions ever get fixed before the hardware is so dated as to be worthless anyway? Some might say that time has already passed… newer competitive hardware with greater ADC resolution obsoletes the AIMuhf.