Mini60 antenna analyser

There seems a never ending stream of low end antenna analysers appearing.

The Mini60 antenna analyser is one in that vein, and is sure to prove popular because of its low price. As is common, there does not appear to be an English language user manual and the specifications in eBay ads are not very reliable (eg weight: 200kg).

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Above is a screenshot from an online demo of the Mini60 on a 7MHz antenna.

Trying to glean some insight into its capability from the display, it appears to show three plots labelled VSWR, R and Z. Since Z is shown as a scalar quantity (when it is really a complex quantity with real and imaginary parts), we might reasonably assume that the quantity display is the magnitude of Z (|Z|).

It appears to not directly display reactance, and although the magnitude of reactance (|X|) can be calculated from |Z| (|X|=|(|Z|^2-R^2)^0.5|), the sign of reactance is not resolved unambiguously.

Find R,|X| from VSWR,|Z|,Ro will calculate |X| from data shown on some of these low end analysers. That calculator will not find a result from the figures shown in the screen shot, VSWR(50)=1.35, |Z|=33, Zo=50, as they are inconsistent… VSWR(50)=1.35 implies that |Z| cannot be less than 50/1.35=37.04. Likewise, it is not possible for R (34) to be less than |Z| (33). All of this speaks to the accuracy of the instrument where displayed results are inconsistent.

The sign of reactance discussed the importance not only to novices but also to experienced practitioners of understanding the sign of reactance in measured impedance, and the need for an instrument to reliably sense and display that sign.

It is little more than a scanning VSWR meter, though that can have its uses. There are times where VSWR is the best information, other times when you want (ie need) to know R,X.

The plot above appears to be for a 1.2m Small Transmitting Loop.

Screenshot - 04_09_2015 , 08_30_19

Above is a free space analysis of such a loop with that VSWR response. Unfortunately, the loop was measured inside a building and the assumption of Rr being the free space value with introduce some uncertainty (perhaps of the order of a few dB in calculated efficiency).