Rigexpert Antscope2 – v1.1.1

A new version of Antscope2 has been released.

Online posters are excited that it supports some versions of nanoVNA, and one thread attempts to answer the questions:

The SWR image shows that the SWR minimum is at the center phase angle as you would expect. My question is:

  1. what are the other points that look like resonance,

  2. and should I trim my antenna based on phase?

  3. If so which one?

They are interesting questions which hint the ham obsession with resonance as an optimisation tartget.

Properly interpreting VNA or analyser measurements starts with truly understanding the statistic being interpreted.

In this case, the statistics being discussed are Phase and VSWR, and their relationship.

What is the Phase being discussed?

Above is an Antscope2 phase plot for an archived antenna measurement. The measurements are of a 146MHz quarter wave mobile antenna looking into about 4m of RG58C/U cable. We will come back to this. Continue reading Rigexpert Antscope2 – v1.1.1

Rigexpert AA-600 N connector dimensions

A recent post by David Knight described dimensional issues with the N connector on his AA-600 and problems with the seller in having it resolved.

Warned of a potential quality issue, I measured my own AA-600.

Above, the test of the inner pin forward surface distance from the reference plane on the N jack on the AA-600. The acceptable range on this gauge for the female connector is the red area, and it is comfortably within the red range.

Above is a table of critical dimensions for ‘ordinary’ (ie not precision) N type connectors from Amphenol.

This dimension is important, as if the centre pin protrudes too much, it may damage the mating connector.

Pleased to say mine is ok, FP at 0.192″.

I used a purpose made gauge to check this, but it can be done with care with a digital caliper (or dial caliper or vernier caliper), that is what I did for decades before acquiring the dial gauge above.

nanoVNA-H – measure ferrite transformer – Noelec balun

At nanoVNA-H – measure ferrite transformer I gave an example of using a nanovna to measure loss of a ferrite cored transformer.

Noelec makes a small transformer, the Balun One Nine, pictured above and they offer a set of |s11| and |s12| curves in a back to back test. (Note: back to back tests are not a very reliable test.) Continue reading nanoVNA-H – measure ferrite transformer – Noelec balun

VSWR ripple

Having seen some recent discussion where the online experts opined that an example given of a VSWR plot that contained a fairly consistent ripple was quite normal, this article suggests there is an obvious possible explanation and that to treat it as quite normal may be to ignore the information presented.

Above is a partial simulation of a scenario using Rigexpert’s Antscope. It starts with an actual measurement of a Diamond X-50N around 146MHz with the actual feed line de-embedded. Then a 100m lossless feed line of VF=0.66 is simulated to produce the plot that contains a ripple apparently superimposed on an expected V shaped VSWR curve.

This is the type of ripple that the expert’s opine is quite normal. Continue reading VSWR ripple

Transformer loss from half return loss

The popularity of the nanovna with new users has led to a lot of ‘beginners’ seeking advice of the online experts.

A recent question and the responses exposes some common misunderstanding / woolly thinking.

A beginner in search of wisdom asked if there an easy way to measure balun loss?

One of the responses was…

Measure the return loss of the balun with the balun shorted. The return loss should be about twice the balun loss. This is similar to measuring the loss of a shorted or open piece of cable.

This was expanded by others, basically supporting the concept. Continue reading Transformer loss from half return loss

nanoVNA-H – measuring an inductor – is it a no-brainer?

Let’s explore measurement of a test inductor with the nanovna.

Above is the test inductor, enameled wire on an acrylic tube.

An online expert’s advice make this task look like a no-brainer:

For a 100 nH inductor you are probably using an air wound coil so you won’t see that much change in inductance with frequency. However, inductors made with toroids will because the permeability of the core goes down with frequency.

So, this is an air cored inductor, permeability is approximately that of free space, a constant 4πe-7 independent of frequency. Nevertheless we will see that apparent inductance can change with frequency. Continue reading nanoVNA-H – measuring an inductor – is it a no-brainer?

nanoVNA-H – continuing USB-C repair

I have reported issue with the USB-C plug / socket arrangement on the nanoVNA-H.

It is very sensitive to any jiggling of the cable or connector, causing a reset of the nanoVNA which almost always means lost work. The supplied cable was a partial cause, but sadly the jack on the PCB is also faulty.

This has progressively gotten worse to the point the nanoVNA-H is unusable. I have had a replacement socket on order for months from China where public health problems are causing chaos, it has only just shipped so could be some months yet.

I do realise that this is replacing cheap Chinese junk with cheap Chinese junk.

Anyway… it finally arrived after many months. A pack of 10 sockets cost $2.30 incl shipping, so it gives one a fair idea of how cheap the low grade connector that was used would have come.

Above, the replacement USB-C socket soldered in to the board without removing the display. The SB1 pad lifted of the board during removal of the old socket, no connection is made to it, so no harm done. Continue reading nanoVNA-H – continuing USB-C repair

Current regulation dynamics of Atten APS3005S

This article documents a simple test to ascertain whether the current regulation dynamics of are good enough to use for testing strings of LEDs as found in much modern lighting

Atten-hcctl00

The APS3005S is a linear bench top power supply 0-30VDC at 0-5A with adjustable voltage and current regulation… so called constant voltage and constant current modes.

A pair of 900mm long small gauge (0.5mm^2) hook up leads were used to apply a short circuit to the power supply, and current was set to 0.1A. The resistance and inductance of these leads will to some extent limit the peak current.

The short circuit was removed and the power supply set to 30V out.

The short was reapplied and the current captured with a current probe. The current probe calibration is 1mV/10mA.

Above, the peak current is 6680*0.1=66.8A, that is 668 times the set value. Continue reading Current regulation dynamics of Atten APS3005S