Should you trust your VSWR meter?

One often sees newbies ask about their VSWR meter readings, and a common observation is that the measured VSWR is better at low power and as power is increased, VSWR increases.

With the evolution of the ‘shack in a box’, and knowledge and experience to match, the problem is often reported observed with the transceiver’s internal VSWR meter.

Some of these ‘shack in a box’ have some pretty nifty features, for example the very popular Icom IC-7300 not only has an internal VSWR meter for the HF bands, but it can perform an assisted sweep and display the results graphically.

Isn’t that a great idea, so convenient, all good!

Or is it?

Scaling from the display, I make the VSWR at 7.160 to be 1.2. But, when an inline better VSWR meter indicates 1.61. Futher, the better meter indicates the VSWR at 7.100MHz is 1.15, not 1.00 as shown on the IC-7300 display.

Examination of how the IC-7300 performs this measurement suggests that it is unlikely that the IC-7300 is faulty, it is a poor design (ie designed to fail).

So, we have answered the subject question “Should you trust your VSWR meter?”

The answer is no, like any measurement instrument, prove that it is trustworthy in the intended application.

If the VSWR meter is designed to fail, why does it fail? A good question to be addressed in another article.