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On Mon, Jan 6, 2020 at 03:06 PM, Aleksander Shalygin wrote:

For an N connector, the seller must have an adapter option with a calibration
kit.
My counterpart. It is very convenient to work. And the BNC option should be
similar.
It solves many technological problems in production. (Apologies for bad
English from Uncle Gogl.)

It is really a good design. I am trying to improve the performance of the current version of nanoVNA 300-900MHz. I will consider using N-type connectors after completing the related improvements. Will also consider letting edy555 make similar attempts in his next-generation VNA.

hugen

At the beginning I added ip5303 to NanoVNA just for my convenience. But I didn't expect it to be so popular with the community. Now I have realized that this design is not reasonable and has been improved in NanoVNA-H rev3.4.

hugen

On Mon, Jan 6, 2020 at 07:09 PM, hwalker wrote:

On Sun, Jan 5, 2020 at 08:57 PM, <hugen@...> wrote:
English translation with the help of "Microsoft Translate" …..

Hope not too much was lost in translation.

- Herb

Thank you for your translation.

hugen

I finally found a few posts relating to this in the archives, and have to agree there's a problem. Someone had measured about 60?A of leakage when off - try measuring this on your unit and see how far it's off. At 60?A, this should last several months without charging - if it's flat in a month, that battery's not holding a charge as it's supposed to. (The Injoinic datasheet for their IP5303 says typical of 100?A quiescent current draw when off.)

IMHO, the charging system with the IP5303 is very wrong for the typical battery capacity of 0.4 to 0.45 Ah. Thus I'm worried about my battery now as I charge it. The battery, if you have a good cable and the power supply can do it, will be taking in a charge greater than 1C. This stresses the battery and likely will cause premature battery failure in cheap batteries.

The IP5303 is so inflexible that the only thing I can think of doing that doesn't waste charge energy is adding another battery in parallel, which will give enough load to balance out its seemingly inability to reduce charge rate for smaller cells. The IP5303 probably is expecting at least 1.5Ah of capacity or so, and likely less than 3Ah.

The power wasteful but simple solution is adding a resistor into the USB charging path to limit charge current. Maybe 0.33 ohms or so. This should improve the life of the battery pack, both cycle count and hopefully prevent pack failure, at the cost of charging time (and a resistor).

On Mon, Jan 6, 2020 at 01:37 PM, Andy wrote:

" .. I had mine charged, and left it on the shelf for a few weeks and it died on me."
===========================================================
All battery powered devices exhibit some self discharge during storage. My cellphones and tablets when completely powered down require recharging after a few days. A few weeks in my opinion is a pretty good shelf life for a 400 mAh device. Both of my NanoVNA's were delivered via slow boat from China, and were in transit for over 3 weeks. Both retained enough charge to power on when they arrived.

Depending on supplier, some batteries may be better quality than others so its hard to make a blanket statement regarding battery performance from a product like the NanoVNA that has multiple suppliers. I noticed hugen's new version 3.4 pcb has a 650 mAh battery instead of a 400 mAh one. This should translate into longer operating time, at least until the 4" display is added.

- Herb

I've noticed that my second unit's battery is starting to swell a bit. Time to swap it out.?

I think the batteries used on the copies of hugens unit are of low quality and are not lasting? as long as they should.? It might also be the counterfeit ip5303 charge controllers on some units as well...the ones that fail to sense load after a while and you need to add the power-on button to pin 5.?

YMMV



On Mon, 6 Jan 2020 at 4:38 PM, Andy via Groups.Io<punkbiscuit@...> wrote: Has anyone noticed that the shelf life of the Nano VNA seems a bit short ?
I had mine charged, and left it on the shelf for a few weeks and it died on me.
Seems to me to be some sort of high quiescent stand-by state possibly through the switch controller ?

Operating life, when charged and immediately used is good though, indicating the battery capacity as being about 400ma.

73 de Andy

Has anyone noticed that the shelf life of the Nano VNA seems a bit short ?
I had mine charged, and left it on the shelf for a few weeks and it died on me.
Seems to me to be some sort of high quiescent stand-by state possibly through the switch controller ?

Operating life, when charged and immediately used is good though, indicating the battery capacity as being about 400ma.

73 de Andy

Google translate had a slightly different but important statement at the end on availability....

"AA6KL is further improving its development. NanoVNA-H with STM32F303CCT6 and 4-inch display will be launched soon. I hope that the community can have more fans"

Looking forward to seeing them on the market before too long...

Roger

This is the weakest element of this device. It has not worked since the beginning. I have 3 weeks. I need information about the type of this switch and where to buy it. I will order 2 pieces.

had the same issue with mine,the flimsy legs snapped off my jogwheel,managed to dremell away the plastic put 3 blobs of solder on the remains of the legs then sweated it back on the pcb,good idea but a crap quality switch!

That is the screen i fitted to mine,works a treat,quite cheap as well.

i found the jog wheel fine to use,just a badly made piece of crap tho!,would be fine if better made!

The errors scale proporionally with wavelength. I use my VNA mainly around 900 MHz in RFID development and applications. Here a single mm path length is on the threshold of an acceptable error for me. So scaling up in wavelength 30 times, we arrive at 30 MHz and 30 mm will be the length of wires that may start to be a source of errors.
Wavelength at 30 MHz is 10 meters, 30mm is just 0.3% of 10 meters. So you're fine if you keep the wires a bit short, or lower the frequency to 3 MHz. Then, it hardly matters anymore. But you can easily measure yourself the return loss of a 50 Ohm resistor connected with alligator clips, and measure short and open. This is the easiest if you calibrate the VNA at the end of the (SMA) cable. Solder the alligator clips with short wires to a female SMA connector.

Op 6-1-2020 om 17:29 schreef entilleser via Groups.Io:

I'm sometimes (often) also mathematically challenged so I perform a sanity check when doing these type of measurements.
Instead of the coil connect a 25 ohm 1% resistor (or some other value different from 50 ohm but not too much) and see if this is indeed being measured as pure 25ohm. There should be no capacitance or no induction. Any deviation will probably also happen when measuring your coil.
This will tell you at least if your calibration using your homemade fixture makes sense.
--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

To the mathematically inclined from the mathematically challenged...

I understand the obsession with eliminating measurement errors. But how much error are we really talking about here? Suppose I take a short piece (say 6 inches) of 50 ohm coax cable, crimp a male sma connector on one end, and a couple of alligator clips on the other end. I "calibrate" with the alligator clips dangling (open), then with a short piece of wire (short), and, finally, with a non-wirewound, 50 ohm 1% resistor (load). Then I go to measure inductance of the coil I hand wound for my crystal radio. Are we talking 1% here? 10%? 100%? 1000%?

I understand that the error in such as setup is going to increase with frequency. But, say, between 3 MHz and 30 MHz...? Below that? Above that?

I also understand that there will be many factors affecting this setup: resistance between the alligator clips and whatever you have clipped into them; random capacitance and inductance from nearby stuff; temperature, humidity, spilling your coffee on it... If the effect of all possible factors affecting measurement using such a setup are just too great to make any kind of ball-park assessment of the range of error, you could just say that.

Thanks, ahead of time, for insight into this question.

Slawomir,
BH5HNU, the developer of the NanoVNA-F, is generally responsive to hardware issues when you bring them to his attention at /g/nanovna-f/messages . You might leave a message for him at the above link and see if he offers any remedies before attempting any repairs.

- Herb

On Sun, Jan 5, 2020 at 04:42 PM, Birdman wrote:

When you purchase on amazon, YOU decide which sellers you purchase from, OR
you let Amazon decide. That could be what you are doing wrong, and why you
report amazon sending you their choice of product. If you click on the
sellers list, you can choose which one you wish to use.

I was referring to instances when the sellers item says "fulfilled by Amazon" and that happens a lot, then you no longer have a choice, they will make it for you, and sometimes there are no other options. I am not new to Amazon either so I am not doing anything wrong, all I am saying is that for me ebay works much better and is much easier to deal with, at least for the US. Not sure about the UK or elsewhere. For a while I compared items of interest on both sites, and sometimes still do, but 90% on Amazon it would usually cost a bit more, or have added shipping costs, so I use them only if there is absolutely no other alternative. The $25 free shipping is also another nuisance when trying to buy small stuff, you always end up having to spend more buying just yet another one or sometimes even two additional small "filler" items that Amazon conveniently provides to make it past the minimum. Classic trick. No such thing on ebay, plus you can safely pay through Paypal with one click. Oh and you get ebay bucks (1% cash back) on almost any purchase...

Good for you if Amazon works well for you. But are you sure you might not be doing something wrong on ebay?
Anyway, thank you for your input and that's it for me on this discussion.

Not claiming I am competent to do this I would like to try to summarize in limited amount of words what this thread has provided

It adds value for VNA measurement, due to its internal transform, to understand the impact of the magnitude of measurement errors (such as noise) or not well characterized calibration standards on the calculated values, in particular to understand the impact pending the position on the Smith chart. (referring to the DERR part of the communication)
It is possible to formulate an elegant, rather compact formula to calculate G solely based on g,s,o,l,S,O and L
It is possible and it makes sense to compare 1 port (S11) measurement performance of two VNA's measuring the same load if these have been calibrated using the same calibration standards and approach (this is regardless if this has been done using SOL or any other calibration approach, the use includes the utilization of the description of the used calibration standards, either as perfect, parameter modeled or data based) as the results of these measurements should be equal.
--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

Hi to all,
a few days I received NanoNVA-F. I bought on Aliexpress. Unfortunately, the rotary switch only worked one way and blocked the functions on the touch screen. I had to undress it but repair is impossible. Does anyone know what type of this switch is and where to buy it? The seller has not yet responded to my complaint.
Happy New Year
Slawomir

On Sun, Jan 5, 2020 at 08:04 PM, Gary O'Neil wrote:
Hi Gary,

I don't know if I can answer your questions, but let me start with the last ones...

This brings up yet another question. If the devices are "measured and
remembered" as the math clearly dictates, what would cause a short and an open
(defined as such) to appear anywhere other than the locations -1 and 1 without
biasing the algorithm to place them differently? If they are intentionally
placed at a different location, what is the justification for doing so, since
this would seem to create a need to compensate for the induced post
calibration offset errors ?

First, it isn't the "devices" that are "measured and remembered", it is the "system errors" that are measured and remembered, so that their effect on measurements can be compensated for. (These "system errors" are separate from any characterized imperfections the Standards might have.)

The Standards are the means by which the system errors are determined. These standards are assumed to be perfect and without error, but not perfect in the sense that the short's reflection coefficient is -1+j0 or the open's equal to +1+j0. Rather, they are considered perfect in the sense that their electrical attributes (delay, loss, parasitic effects) have been accurately characterized and are known to the VNA system. In other words, perfect, yet imperfect.

If one of these "perfect yet imperfect" standards is then measured on the VNA, prior to the VNA's calibration, the position of its Reflection Coefficient, plotted on the Smith Chart, will be quite different from what it should be. This difference is due to the VNA's "system" errors".

There are three system errors associated with one-port (i.e. S11) measurements. Thus, to determine what these three errors are, three different "known" standards are used, creating three equations with three unknowns, those unknowns being the unknown system errors. These equations are then solved, and the unknown errors become known.

(For more on this, see here: )

Now that these three errors are known, they can be compensated-for (i.e. corrected) in future measurements. And if I now take one of my "perfect yet imperfect" standards and measure it on the VNA, the VNA should now accurately place its Reflection Coefficient on the Smith Chart.

But should it be placed at -1+j0 or 1+j0?

Let's say that this standard is a Short standard, and let's say there is some inherent, yet well characterized, delay within the short itself, between the actual implementation of the short and the calibration reference plane (that lies within the short's connector). The VNA should not plot this short at -1+j0, but should instead plot the short at the point on the Smith Chart that represents the *actual* impedance of the Short at its reference plane, which is *not* -1+j0 (because the delay will cause rotation). Dr. Kirby's example is a good illustration of this concept.

Let's take another example: the Open standard. These standards have some amount of fringe capacitance, and so let's assume that our Open has some fringe capacitance but no delay.

Now, after our calibration procedure, let's say we were measuring an unknown capacitor that, by coincidence, had *exactly* the same amount of capacitance as the fringe capacitance of the Open. Would we want this capacitor to be plotted at +1+j0? Or would we want it to be plotted at some point, not 1+j0 , that represents the actual Reflection Coefficient for that capacitance?

We would want it to be accurately plotted at the point representing the value of the capacitance. And since, in this example, there is no difference between my "Open" standard and the capacitance I later measured, if I then measured my Open standard on the VNA, its Reflection Coefficient should also appear at that same point on the Smith Chart as my unknown capacitor, not at 1+j0.

I hope the above explanation helps answer your two questions. Please let me know if I've been confusing or not clear. And then, once we get through this concept, we can tackle your other questions.

Best regards,

- Jeff, k6jca

P.S. it is rare for a standard to have zero delay from its reference plane. APC-7 standards, being sexless, have 0 delay, but almost all other standards have some sort of non-zero delay and thus, when measured, should not appear at -1+j0 or 1+j0. So almost all open or short standards, when plotted, should plot rotated from -1+j0 or 1+j0.