Whilst preparing A first test of the FA-VA5 antenna analyser, issues were noticed with the user interface design / implementation. I stated in a later article that The matter of the clumsy / unproductive user interface will be explored more at a later time.
This article introduces a short video demonstration of the frustrating / unreliable user interface (UI) in firmware v1.08 where buttons do not seem to operate intuitively and consistently.
The directional coupler at top left contains half wave peak detectors for forward and reflected waves. They are wired to the two compensated op amps at lower right (the connections are not shown on the circuit as the coupler may be remote, follow the terminal designations). Continue reading Should you trust your VSWR meter – linearisation
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.
This article started off as a video demonstration of measuring the Matched Line Loss (MLL) of a 6m length of old / budget grade RG58CU for comparison with the datasheet.
Using the instrument was such a frustration due to the user interface design / implementation, but more time was devoted to trying to understand it and experimenting with button press timing etc… but I must admit, to no avail. I persevered and made the measurements which are reported here, the matter of the interface issues will be dealt with separately.
So, the interpolated datasheet MLL for quality cable, Belden 8262 (RG58C/U), is 0.319dB.
The measurement technique is the measure the ReturnLoss of the DUT with o/c and s/c terminations, and estimate MLL=(RLo+RLs)/4.
The analyser is a low cost kit (~A$265 including high accuracy cal kit and postage), the SM components are already fitted to the PCB, but the other components like switches, display connector etc need to be fitted. Whilst these parts are hand soldered, some pins are quite close to other components and require a fine soldering tip and steady hand. It is probably an hour’s work to complete the assembly.
Above is the completed FA-VA5. As can be seen, it has just three buttons which are used to navigate a menu system and to perform data entry, both of which can be a bit tedious but that is the trade off for a simple user interface.
AIM915 was recently pulled from the distribution site and replaced by a new release, AIM915a.
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 AIM915, it persists in AIM915a.
Let’s review the internal consistency of this part of the display screen.