nanovna-H – mobile UHF antenna VSWR sweep

The NanoVNA is a new low cost community developed VNA with assembled units coming out of China for <$50.

This article documents a task to perform a VSWR sweep of a UHF mobile antenna.

The nanovna-H has firmware NanoVNA-H_20191018.dfu installed.

The instrument was OSL calibrated for reflection at Port 1 (Ch0 is nanovna speak, convention means little) for 100-500MHz.

A sweep was then performed from 400-470MHz, forcing some interpolation of the calibration data.

The nanovna was configured for VSWR and Smith chart displays, much as you would to use it stand alone, but I did have it attached to the computer to capure the display (it seems it cannot be saved for later playback).

Above, the captured display. The results are pretty much as expected, no surprises there. Continue reading nanovna-H – mobile UHF antenna VSWR sweep

nanovna-H – a ferrite cored test inductor

The NanoVNA is a new low cost community developed VNA with assembled units coming out of China for <$50.

This article documents some tests using a small ferrite cored test inductor that provides a similar impedance to that of a common mode choke suited to HF antenna feed lines.

The nanovna-H has firmware NanoVNA-H_20191018.dfu installed.

A small fixture was OSL calibrated and impedance measured by reflection (ie s11).

The results broadly reconcile with previous measurements of the inductor, but the jitter is worth of examination.

Above is a chart from nanovna-saver showing the measured impedance components, we might expect a reasonably smooth curve for each. It has a lot of jitter on it, and you might excuse that as a result of applying the instrument and method to such a high impedance… but for two things: Continue reading nanovna-H – a ferrite cored test inductor

nanovna-H – first experience

The NanoVNA is a new low cost community developed VNA with assembled units coming out of China for <$50.

It is a semi open source project, some information is published in open access places like unrestricted github and currently unrestricted acccess messages in a io.groups forum, but the wiki and files collection of that forum is by membership only and so is not publicly available.

After reviewing a lot of public information, I chose to try  purchase an Nanovna-H. There were trials along the way in that Hugen79’s preferred supplier on Alibaba could not accept my suburb in the address, so I searched eBay, Amazon and Aliexpress for items that appears to be a Nanovna-H. On the day, eBay and Amazon had no listings, but there were some on Aliexpress.

In this case, though the seller lied about material things, it does appear that I received a ‘genuine’ nanovna-H, and one of very recent manufacture as it had firmware dated two days after I placed the order.

The device was charged and needed only an hour to reach full charge, it was about 75% charged. No grief with the battery manager stuck in shutdown (yet) as some users report.

Above, the nanovna-H as received. Continue reading nanovna-H – first experience

nanovna-H – occasional glitches in measured data

The NanoVNA is a new low cost community developed VNA with assembled units coming out of China for <$50.

I purchased what appears to be a ‘genuine’ nanovna-H and it has firmware NanoVNA-H_20191018.dfu installed. During checkout of the delivered device, an issue became evident, an issue worth describing in its own article.

Glitches on the displayed data are occasional, but hardly rare, and are a concern.

The nanovna was OSL calibrated (is for reflection only) from 1 to 500MHz and the cal save in C4.

On repeated scans of the SC used for the cal, there are obvious occasional glitches evident on various PC clients.

Above is nanovnasharp v1.03. An expanded scale shows the observation, an occasional single measurement, always with a downwards glitch  of |S11|dB of variable magnitude, but usually less than a couple of dB. Continue reading nanovna-H – occasional glitches in measured data

RG6/U with CCS centre conductor at HF

at Series match for a half wave dipole I mentioned that RG6/U may have a copper clad steel (CCS) centre conductor, and may have significantly more loss at HF than expected based on datasheets and calculators.

Above is a comparison of matched line loss based on measurement of a length of RG6/U Quad Shield CCS cable and prediction from Simsmith of Belden 8215 (also CCS). The ripple is due to measurement system error. Continue reading RG6/U with CCS centre conductor at HF

Series match for a half wave dipole

An online poster was demonstrating the effect of varying line length on a half wave dipole on VSWR(50) and by mistake configured the line be of of Zo=75Ω.

He asked the question

In the general case, if you are trying to match 50 Ohms, would you be better off feeding a normal backyard dipole with 75 Ohm coax if you are willing to prune it to a specific length after the fact?

Continue reading Series match for a half wave dipole

Rigexpert AA-600 reference plane

The Rigexpert AA-600 has an inbuilt calibration which is convenient to use. It is capable of OSL calibration, but this article discusses only the inbuilt calibration.

The reference plane is the plane at which the instrument calibration is correct, at other locations there is a transmission line impedance transformation applied.

The pic above shows the reference plane, but where exactly is it and why do you want to know? Continue reading Rigexpert AA-600 reference plane

nanoVNA MOD v3 – a first look

Since I have a nanovna-H coming on a ‘slow boat from China’, whilst working with a Touchstone s1p file exported from Rigexpert’s Antscope I tried to open the file in nanoVNA MOD v3.

Above, the outcome was not good. The name of the loaded file is not shown, there were no messages during loading, and an empty graph and the stimulus data does not match the file. Continue reading nanoVNA MOD v3 – a first look

nanovna – a first plunge

The NanoVNA is a new low cost community developed VNA with assembled units coming out of China for <$50.

It is not really a project as such, but a loose collection of hardware versions manufactured in variously compliant forms, and several PC and web clients competing for space. Information is partly in the public domain, partly in restricted access forums where the controller’s identity is hidden… the modern way of ham radio.

After some research, and with some residual uncertainty, I decided upon the so-called nanovna-H design by Hugen79

Hugen79 nominates a seller on Alibaba, but I was unable to purchase there because it would not accept my suburb in an address, and unwilling to put at risk the minimal buyer protection by purchasing outside of the selling platform, I went to Aliexpress for sellers. (No listings on eBay or Amazon for AU account holders, but many listings have appears on eBay since purchase).

Aliexpress is a platform by the Chinese for the Chinese, and from experience I am too well aware of the high risk of scammers and cheats leading to loss of one’s money. I decided to exceed my self imposed limit of A$30, a risk management strategy, and spend the $85 required by a seller offering free returns (whatever that means).

Above is the pic from the seller’s listing. Continue reading nanovna – a first plunge

Walter Maxwell’s teachings on system wide conjugate matching – a SimSmith example

I have written on Walt Maxell’s proposition about simultaneous system wide conjugate matching in antenna systems. I will repeat a little to set the context…

Walt Maxwell (W2DU) made much of conjugate matching in antenna systems, he wrote of his volume in the preface to (Maxwell 2001 24.5):

It explains in great detail how the antenna tuner at the input terminals of the feed line provides a conjugate match at the antenna terminals, and tunes a non-resonant antenna to resonance while also providing an impedance match for the output of the transceiver.

Walt Maxwell made much of conjugate matching, and wrote often of it as though at some optimal adjustment of an ATU there was a system wide state of conjugate match conferred, that at each and every point in an antenna system the impedance looking towards the source was the conjugate of the impedance looking towards the load.

This is popularly held to be some nirvana, a heavenly state where transmitters are “happy” and all is good. Happiness of transmitters is often given in online discussion by hams as the raison d’être for ATUs, anthropomorphism over science. Continue reading Walter Maxwell’s teachings on system wide conjugate matching – a SimSmith example