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Erik
Congrats with your Call

73's
Erik ON8DC

Additional tidbits of information.

1. The V2 PCB is 4 layers.
2. The schematics will be posted soon, at the same time as the launch on taobao,
3. Design objectives include keeping BOM cost below $100 and compatibility with current software base.

Rather than larger, I was hoping for wireless (Bluetooth), perhaps by ESP32,
using a smartphone or tablet for display and complex calculations
without USB and ground loop concerns.

Hello,

Allow us, please, to inform you that, after:

[15] : /g/nanovna-users/message/3147

we just uploaded our well-formed mathematical expressions
of full-one port vna measurements [*] :



which--due to their apparent symmetries, as well as to their
arrangement--we consider them as the most economical and
appropriate ones for programming them in any computer
language - either having the complex data type internally or not.

Sincerely,

yin@pez@arg

[*]

16

On Mon, Sep 23, 2019 at 08:04 PM, <erik@...> wrote:

Can you show the measurement? preferably the smith chart of another VNA doing
the CH0 measurement.

I'm talking about OUTPUT impedance of CH0 (don't confuse with INPUT impedance). I didn't hear that it is possible to measure output impendance with another VNA :)

You're needs to measure amplitude on different loads and then calculate source impedance:

Z = (R1 - R1*(U1/U2)) / (U1/U2 - R1/R2)

My measurements for CH0 in attachment. R1 = 1 MOhm, R2 = 50 Ohm. Of course this is just a draft measurement for overage amplitude. I'm too lazy to perform measurement for specific frequencies. :)

I understand and thank you for answering.

On Tue, Sep 3, 2019 at 11:36 AM, RFy wrote:

Any genius/proper methods of measuring over 30dB powered source impedance?

In order to measure source impedance, you're needs to measure amplitude for different loads. Since many RF PA cannot handle open output properly you will need to use two different loads which impedance is compatible with PA output. For example 25 Ohm and 75 Ohm. If your PA has very limited range for load impedance, use something like 40 Ohm and 60 Ohm. The goal is to get more different load to get more precision.

So, you have load R1 and load R2.
Just connect R1 and measure amplitude U1.
Then connect R2 and measure amplidue U2.

Now you can calculate source impedance:

Z = (R1 - R1*(U1/U2)) / (U1/U2 - R1/R2)

The only problem here is to measure RF signal amplitude on the load properly. This is not so easy task. You can use wide bandwidth oscilloscope for that.

PS: there is no difference if your equipment measuring RMS voltage or amplitude voltage, just use the same voltage type for both measurement.

PPS: you're needs to measure voltage on the load. But note, you cannot use random wires to do that. The better way is to use high impedance RF probe from oscilloscope. The other way is to use attenuators with 50 Ohm output and RF voltmeter with 50 Ohm input. The main goal is to measure voltage on specific load.

Never mind, figured it out. THanks if you looked!

On Fri, Sep 27, 2019 at 12:04 AM, <epif18@...> wrote:

I downloaded 1.03 and everything seems to work except the smith chart won't
draw on my PC.

Try this one:

I also have more fresh with fixed some bugs and TDR screens.TDR VSWR works great, but TDR Z (step response) still not works properly

Thanks Neil. I downloaded 1.03 and everything seems to work except the smith chart won't draw on my PC. Data comes in on all modes. Is there an install process. BTW, I was in the process of designing and building a VNA but now why bother. Works great !

It is a screen protector that prevents the screen from getting scratched during assembly/storage, etc. peel it off if you want to

That green tab might be to disable the battery during shipping??

Sent using




---- On Thu, 26 Sep 2019 17:00:15 -0400 mike watts via Groups.Io <wy6k@...> wrote ----


My unit arrived with a small green plastic tab sticking out the top near the left side.? What is that all about?? Do I remove it?
Mike WY6K


"... somewhere in the distance, there's a tower and a light, broadcastin' the resistance, through the rain and through the night..."

Mike,

It's probably the cheap screen protector that's on it.

Dave-KB1PVH


Sent from my Galaxy S9

On Thu, Sep 26, 2019, 5:00 PM mike watts via Groups.Io <wy6k=
[email protected]> wrote:

My unit arrived with a small green plastic tab sticking out the top near
the left side. What is that all about? Do I remove it?
Mike WY6K


"... somewhere in the distance, there's a tower and a light, broadcastin'
the resistance, through the rain and through the night..."

My unit arrived with a small green plastic tab sticking out the top near the left side.? What is that all about?? Do I remove it?
Mike WY6K


"... somewhere in the distance, there's a tower and a light, broadcastin' the resistance, through the rain and through the night..."

On Thu, Sep 26, 2019 at 09:08 PM, Palo wrote:

Would it be possible to implement some of the features of this project into
NanoVNA?

No, it is impossible, because NanoVNA uses much more slow CPU with much less memory.

EU1KY uses hardware with powerful STM32F746G processor working at 216 MHz with high performance DSP core, 340 kB internal and 8 MB external RAM, 1 MB flash and many other features.

NanoVNA uses very cheap STM32F072CB processor working at 8 MHz with 16 kB RAM and 128 kB flash. There is no resources to implement all these features.

But some of these features may be implemented as separate firmware with dedicated mode for specific feature.

Current NanoVNA TDR implementation is almost useless, because it shows time with 1 nanosecond resolution.

I experimented with different FFT sizes and it looks that 65536 has the best resolution for NanoVNA. It allows to see picoseconds. But it produce a lot of data, it's better to use 32768 points. 16384 also usable, but insufficient resolution becomes noticeable.

This TDR feature just eats precious memory. F072 has too small memory. So, I think it's better to remove TDR function from firmware and replace it with more useful features

One thing I noticed about the screenshot attached to the first post, is the TDR function seems to involve some human interaction. The first peak is a false positive and the cursor at the second peak was the true cable length reflection. There is probably not enough memory to make it a hands off calculation like Rune's NanoVNA Saver performs.

Hello,

Allow us, please, to inform you that we just
uploaded the following two, very rare, references:

[1] Richard H. Hackborn, "An Automatic Network
Analyzer System", Microwave Journal, May 1968, p.47 :


[2] Paul Schmitz, "Vector Measurements of High
Frequency Networks", HP 5958-0387, 5481, 1989, p.3-9 :


which, unfortunately enough, justify fully the writings at [7][3]:
/g/nanovna-users/message/3004

although, some honorable members of this forum
considered them as outrageous allegations of the
insulting kind.

Sincerely,

yin&pez@arg

15

Please be specific. I have no time to study the differences

On Thu, 26 Sep 2019 at 15:16, Dr. David Kirkby <
drkirkby@...> wrote:

Lithium ion batteries can fail with catastrophic consequences.

I know that the switch on the NanoVNA is of appalling quality, but I will
address that by an external switch.

The screen on the first NanoVNA I received was faulty - a problem Hugan
said is common.

A quick look found me this battery



a very reputable manufacturer, around 5 times the stated capacity of those
with the NanoVNA, at a cost of about 50% of the cheapest NanoVNA I have
seen.

This one is just ?0.01 extra, from the same place,

but 3.45 Ah.

Based on someone reporting getting 2 hours from a 450 mA hr battery, that
should last 15 hours, so a good full days work for sure.

--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

More time domain samples will not provide better resolution because of the upper frequency limit. However, if the UI allowed picking a peak on the time domain display, one could window that in time, Fourier transform and do a linear fit to the phase to get the delay time and display that.

For peaks which are close together, the Rayleigh criterion set by the maximum frequency is the best you can do. However, the phase fit is most easily done with just a single peak. For an isolated peak the phase resolution and wavelength of the highest frequency measured determines the spatial resolution. I doubt that the velocity factor sufficiently consistent to do better than a few cm.

A basis pursuit will resolve closely spaced reflections, but that's not something that an STM32F series MCU can do.

Off the top of my head, I don't see a way to solve d = a0*exp(j*2*pi*f*t0) + a1*exp(j*2*pi*f*t1) by least squares. Though you might get close enough by estimating a0 & a1 in the time domain and only solving for for t0 and t1.

I wish I had time to work on this more, but other tasks must be attended to.

Have Fun!
Reg