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Isn't there a minimum frequency on those DDS signal generator chips. There is no need to put range smaller 101 times than that.

Hello,

To use my NanoVNA-H as a generator. can i find a PC software using the a command similar to the "CW" manual function ?

Thank you for your help.

73 QRO,

Rudi HB9ARI

Hi,

thank you, Dana, for that clarification: Return Loss in a passive lumped element circuit is positive, indeed.

I very much agree with that. There are, however, so many opinions and publications around. I think,
that the attached paper from Prof. Dr. Trevor S. Bird, former IEEE chief editor, is a very good one on that
matter. I suggest to earnestly detail seeking, wondering NanoVNA user's to read it. So here it is attached.

The issue, however, goes beyond that. Please have a look at page two, where another very common error
went unnoticed even in the quote used by Trevor S. Bird:



In this quote Trevor missed his article’s main point, that Return loss must be positive in a passive lumped
element circuit, what definitely he tried to show. Enter complex values for some Z1 and Z2 and you can find
by application of complex math, that you easily get negative return loss. I emailed that to him, but he replied
that while obviously my point appeared to be true, at present he didn’t have time to carefully check that.

An obvious example:

(Please also use other, less simple, also non-resonant values for Z1 and Z2 yourself,
and use a math program that can handle complex calculation like EXCEL.)

Think of a simple resonant circuit on your lab table made of (serial) lumped elements only:

Generator (or Thévenin equivalent) impedance: Z2 = R2 + jX2 = 50 +j100 Ohm,
Load impedance: Z1 = R1 + jX1 = 100 –j100 Ohm.



Because of X1 cancelling X2 at resonance, obviously SWR = 100 / 50 = 2.
The Magnitude of the ‘Reflection’ Coefficient = 0,33333.

That’s easy, right? (Then correctly Return Loss = + 9,54 dB)

But if we use the Return Loss formula quoted for the two complex impedances, we would assume
reflection where there is none. By using the formula nevertheless, we will get

Return Loss = - 2,76 dB
(and ‘SWR’ = -6,34) instead.

And that in a simple passive R-C-L circuit !

We probably will agree: That is wrong.


I carefully studied this controversial issue in great detail. So what actually is the reason that so
often this gets wrong?

Here is my answer:

1. The first sentence above is true for transmission lines with a complex characteristic wave impedance Z2,
terminated by a complex load Z1.

2. The last sentence ?More broadly …“, however, makes a wrong assumption that so far never was proven.
I challenge everyone to do this proof. I predict: You will not be able to prove this

wrong assumption:

“More broadly we can set equal the terminated transmission line’s characteristic wave Z2 impedance to a generator’s
internal complex impedance Z2. Both physically are identical or interchangeable and thus the formula applies to both.”

These two values, however, physically are two different things that ever so often are confused – thus falsely allowing
negative return loss for a passive lumped element complex mismatch.

While on a transmission line we have waves traveling in both directions, incident and reflection, along the length of the
line, at the juncture between a complex impedance generator and a complex load there is no such distance, and hence
we also must use a different approach for derivation. There is actually no reflection, as (for simplicity I use a serial circuit)
all parts share one single and thus identical common current in one direction only. So a ?reflection“ factor doesn’t apply.
No real energy actually is reflected – it all flows in one direction from generator to load and is dissipated in the real part of the load
according to R times the square of that common current I. Depending on the mismatch, less power will be transferred than could be
drawn from the generator, if maximum real power transfer is wanted (which in a vast majority of cases applications is aimed at, but
in reality antennas sometimes are used way out of resonance).

It makes me shake my head, how this erroneous assumption became so omnipresent. How could that be?
It even made it into the ATIS standard glossary - and thus spreads like unproven assumptions in fake news do:



But what then is correct?

Here it is, if we keep here – just for comparison purposes – what actually is a misnomer (as there is no reflection) the name “RC” :



With the asterisk meaning conjugate complex.

Should you want the derivation, let me know – I sure have it.

But I don’t want this to get more lengthy than it is already now – forgive me that, please.


Can you agree? Or perhaps Not?

If not:

Would you please prove to be true anyway what above I called a wrong assumption.


73, Hans
DJ7BA


















-----Ursprüngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von Dana Whitlow
Gesendet: Montag, 1. Juni 2020 12:41
An: [email protected]
Betreff: Re: [nanovna-users] Presentation on the NanoVNA for the Raleigh Amateur Radio Society



I began looking through the presentation on the nano, and immediately caught an error in the table comparing "ham conventions" versus "More modern conventions".



For "no reflections" the correct return loss expressed in dB is a positive infinite value, not negative as shown in the table.

More pragmatically, the return loss of any passive device is a positive number of dB. For example, a "pretty good termination"

might show a return loss of +32 dB.



I know that many people get this wrong. But if you pay attention to the meaning of the word 'loss', then a negative value in dB really means a gain (reflected signal more powerful than the incident signal), which really is possible for active devices like amplifiers etc.



I once gave a demo of a home brew Time Domain Reflectometer

(TDR) at a club meeting, and finished up with a DUT which I had lovingly crafted with a tunnel diode to produce return gain over a wide band. I showed this, pointing out that the reflected signal was larger than the incident, then challenged the audience to say what was in the box. Only one guy got it right.



Dana (K8YUM)







--
Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft.

Thank You for the share.....WD4PVE

I began looking through the presentation on the nano,
and immediately caught an error in the table comparing
"ham conventions" versus "More modern conventions".

For "no reflections" the correct return loss expressed in dB
is a positive infinite value, not negative as shown in the table.
More pragmatically, the return loss of any passive device is
a positive number of dB. For example, a "pretty good termination"
might show a return loss of +32 dB.

I know that many people get this wrong. But if you pay attention
to the meaning of the word 'loss', then a negative value in dB
really means a gain (reflected signal more powerful than the
incident signal), which really is possible for active devices like
amplifiers etc.

I once gave a demo of a home brew Time Domain Reflectometer
(TDR) at a club meeting, and finished up with a DUT which I had
lovingly crafted with a tunnel diode to produce return gain over
a wide band. I showed this, pointing out that the reflected signal
was larger than the incident, then challenged the audience to
say what was in the box. Only one guy got it right.

Dana (K8YUM)

Hi Bill

No problem at all , thanks for the reply anyhow, I could make one myself on a piece of prototype board. Sorry for writing in Dutch in my first message, the Google translation was perfect !

73

Jos

Op 31-5-2020 om 22:23 schreef Bill Buoy:

RTC (Real Time Clock) module on stm32 processor can run from:
LSI generator (old NanoVNA settings). LSI run while processor power on, then power off by switch and only vbat power on, LSI generator suspend and RTC not tick, time value stay while power on vbat pin exist. Its a hardware limits of stm32
Then power on, Time continue tick from stopped value.

If use LSE generator, then need install 32.768 kHz quartz on PC14 and PC15 pin, and enable use it for RTC by software. LSE generator continue work then power off by switch, while power on vbat exist (also LSE frequency more stable). So time value always correct.

RTC clock use by filesystem for set correct file create time, and set name (for better navigation on card, need only sort by name or creation time)

So if installed quattz, better use LSE variant (but possible and LSI), if not installed - use LSI variant (LSE possible not launch, ChibiOS on init wait LSE ready).

RTC works without quartz using the NanoVNA H4 v0.9.3.2 beta - SD Card LSI_Clock.dfu firmware. (# 13941)

Anyone with the NanoVNA-H4 has the option to save the results of their work to the microSD card after installing the firmware further developed by DiSlord.
That is, you can save the screenshot or the measurement graph in .s1p and .s2p format under the SD Card menu for further use. You can find the socket type of the microSD card in an earlier message (# 13750), it is difficult to replace with another (very thin plastic holds the contacts) so it needs a handy hand.
It uses a timestamp generated by RTC to name the files.
The RTC (Real Time Clock) operation must be soldered to a 32.768 kHz quartz (~ $ 0.1) at PC14 and PC15 (H4 v4.2 PCB P3 connector).
RTC works without using the NanoVNA H4 v0.9.3.2 beta - SD Card LSI_Clock.dfu firmware. (# 13941)
Terminal program can be used to enter the date and time is clearly shown in the attached image.

--
*** nothing is permanent only change ( ) ***

The link works. It ask for you to send a request. I assume that he'll grant
permission once a request is made.

I'm looking forward in reading through his presentation.


On Sun, May 31, 2020, 5:51 PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:

Link does not work. Asks for sign in to Google.

Roger

Here is the link. It should not require permission. Try it again. Apologies.

I think you need to share it. Requesting that I ask for access.

Hank
W6IR

Link does not work. Asks for sign in to Google.

Roger

I have an introduction to the NanoVNA with examples of antenna analysis, component analysis, TDR, and balun impedance measurement. It can be found at



I attempted to put this into the files section but I kept getting server timeout errors. Hopefully this presentation will help hams get more out of their NanoVNAs.

73,
Dan
KW4TI

Good day, Jos,
Glad you liked the project. I’m not actually selling these, I only offered the design files so others could have the boards made locally or order them from OSH Park, a pc board vendor in The USA.
I am not financially able to order large enough quantities to make it practical for me to stock them and to cover the shipping costs.

excuses voor mijn vertaling, geef Google de schuld ?

Goedendag, Jos,
Blij dat je het project leuk vond. Ik verkoop deze niet echt, ik bood alleen de ontwerpbestanden aan zodat anderen de borden lokaal konden laten maken of ze konden bestellen bij OSH Park, een leverancier van printplaten in de VS.
Ik kan financieel niet voldoende grote hoeveelheden bestellen om het voor mij praktisch te maken om ze op te slaan en de verzendkosten te dekken.

Hi Vaclav,

I don?t know if you are aware that the nanoVNA can be connected to an Android phone so you can see the graphics in a better screen and also store it in the phone.

This was my reason to buy one nanoVNA with the small screen.

Some vendors include the necessary cable in the "gift box", but it can be purchased inexpensively almost anywhere.

Regards,

Ignacio EB4APL

--
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.

Thanks for the comments on the screen size.
I have spent last few months playing with Bluetooth and planning to add BT technology to the NanoVNA.
I was hoping that somebody will "update" the processor which would include BT or other wireless technology.
It seems most updates are to increase the frequency range, which is of no interest to me.

When I started on that I had real headache "working" with NanoVNA OS without having access to the hardware.
It will be non issue after I get my NanoVNA.

Turn on close caption and select english translation.

Is there an English translation of this presentation?

--
This email has been checked for viruses by AVG.

See this video, , it shows the differences between in measurements with / without antenna cable. In short the low swr frequencies are not effected, the not matching frequencies looks better with antenna connected

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Rudie
VR2WRD