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. 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, enamelled 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

nanoVNA-H – continuing USB-C woes #2

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.

Replacement of the USB-C socket will be difficult, fortunately it is the 12/16 pin version rather than the full 24 pins… but I do wonder at the wisdom of using a USB-C over the proven micro USB connector.

Above, the old socket has been removed from the board. One pad came off with the socket, but it is the unused SB1 pad. Of greater concern is whether the slight movement of the some other pads might cause conductor cracking. I do see signs that a couple of pins might not have tinned the full pad area, a hint of low quality board fabrication and a possible contribution to intermittent connection.

An alternate recovery is to cut the end off a USB cable and permanently wire it directly into the board.

So for now, the nanoVNA-H awaits parts again.

Windowed ladder line – single core CCS 21% IACS

There is some evidence that the common 1.024mm (#18) single core CCS windowed ladder line advertised as 30% IACS conductivity supplied recently may be closer to 21%. This is based solely on comparison of measured DC resistance with specification, but that is a strong hint that the copper cladding is less than specification.

Theoretical prediction

This article presents a theoretical prediction based o A model of current distribution in copper clad steel conductors at RF of the matched line loss (MLL) at 1.8MHz.

The assumption is a 1.024mm steel cored conductor with 30.7µm copper cladding.

Above is a plot of the predicted current magnitude and phase distribution in the conductor. Continue reading Windowed ladder line – single core CCS 21% IACS

W551 CCS windowed ladder line – a guide to low end loss

At Simsmith bimetal line type – a comparison around the first MLL minimum I reported calculated matched line loss vs cladding depth for a single core copper clad steel conductor in a feed line such as Wireman 551.

The common assumption is that as frequency is reduced, so is loss, and at low frequencies loss is roughly proportional to square root of frequency.

That model is for homogenous conductors with well developed skin effect and is not applicable to the CCS line under discussion.

Above is a plot for various cladding depth on a 1.024mm (#18) 30% IACS (67µm cladding) CCS conductor at 1.8MHz where skin depth δ is 49µm. MLL is minimum around cladding depth 100µm or 2δ. Continue reading W551 CCS windowed ladder line – a guide to low end loss