开云体育

Hi Herb -

I would like ask if the larger flash memory will allow the firmware to
generate more than the current 101 calibration points in a way that does not
break backwards compatibility with current software?

It would require some additional code for a single firmware to dynamically detect whether installed with more flash,
then conditionally increase that 101 limit. Of course, that additional code could be problematic for current nanoVNAs..

Alternatively, the code base could have conditional code by compiler pragma and separate firmware loads for larger and smaller flash.

[#97]

On our Comparison of our [NanoVNA] with our [HP 8505A]
Using the Ultimate Criterion of Cross-Ratios

Dear all,

It is our great pleasure and honor to present to you our
results - which we just got for the very first time - of our
Comparison of our [NanoVNA] with our [HP 8505A] Using
the Ultimate Criterion of Cross-Ratios [#96].

We hope that the Great Significance of these results shall be
made crystal clear as soon as you will take into account that
the

* T h e o r e t i c a l * E x a c t * V a l u e *

of this ratio of cross-ratios is:

Modulus = 1

Argument = 0

while, comparatively to this Exact Value,

our * E x p e r i m e n t a l * R e s u l t s * are:

Modulus : Min = 0.98 and Max = 1.01

Argument : Min = -0.07 and Max = 2.10 - in Degrees,

at those, previously mentioned [#95.3], eight 8 frequencies,
as follows:

Modulus:


Argument:


Finally, allow us, please, to additionally emphasize that
these results are substantially independent [#96] of the
four loads we used, that is of their nominal values and
of their uncertainties, this comparison regards both of our:

[NanoVNA] and [HP 8505A]

* p e r * s e * .

We wish you a Happy New Year 2020 !

Sincerely yours,

gin&pez@arg

REFERENCES

[#96]:The Ultimate Criterion for Endless Reliable VNA Comparisons
28 December 2019 - /g/nanovna-users/message/8749

[#95.3]: On the Sufficient Conditions for Identical Measurements Using
Two Substantially Different VNAs - Our Research has been Completed
27 December 2019 - /g/nanovna-users/message/8669

[97#]

I too have power problems, perhaps not quite the same as yours.
I also have two units, a black and a white.? The black one behaves normally most of the time but occasionally will switch off.? I cycle the power switch and all is usually okay.
The white one sometimes will not come on.? I pull out the charging cable and then it works.? At that point I can plug the cable back in and all is well.
The black one gave me problems and I foolishly replaced the power controller IC.? It didn't fix anything but in the process I created other problems which have workarounds so no big deal.
If the battery runs down, the unit will switch off.? That apparently was going on with my black unit but the reason it ran down was that the USB connector was shorted.? I removed the connector and the short disappeared, although the connector seems fine.? I may attempt to solder it back but it's a tough job.? Meanwhile I installed a power cable so I can run it that way, albeit without any data transfer.
The USB C connector has two sets of pins which have to be installed in pairs to obtain reversible operation.? I may forego that and install only alternate pins due to the infinitesimal spacing, too tiny for my eyes or tools.
Bob K6DDX

hugen,
per your GitHub info:

"This is my attemp to port the STM32F303CCT6 to this popular NanoVNA project. The benefits are larger SRAM 40KB from 16KB, larger flash 256KB from 128KB, faster CPU clock 72MHz from 48MHz, and floating point accelerator."

I would like ask if the larger flash memory will allow the firmware to generate more than the current 101 calibration points in a way that does not break backwards compatibility with current software?

- Herb

Establishing a "measurement plane" makes the impedance or admittance displayed on the VNA valid at that specific point. For example, you want to know what the impedance is at the input of some device. You select a transmission line that will reach the device's input and you perform the open,short, load cal with a cal kit of the appropriate connector type for the device under test. Now the impedance measured is the impedance at the device under test's input. Maybe the device under test can be connected directly to the device under test so no cable is needed so the OSL cal is done right at the VNA's test port.
Now if you are simply measuring SWR or return loss the exact location of "measurement plane" is not that critical if its location is not too far down some lossy or poor cable of a different characteristic impedance, etc. (the SWR and the RL remains basically constant along a short transmission line)....Impedance is another thing unless you plot things on a Smith Chart and rotate to the "measurement plane".
Respectfully, I see a lot of discussion about calibration in this discussion group and I think the subject is being overly complicated. The only time I had to get wrapped around the axle is when I had to performance test a VNA in a cal lab. (when I worked at HP/Aglient from '77 to '01, we verified ALL of the published specs and stood behind them so we had to be very careful using the methods and equipment specified by the manual).
With this NanoVNA I think the results have been excellent. I have done a lot of tinkering with impedance matching using it and the measured impedances and the L and C's calculated to perform the matching have worked very nicely.

The easiest one to explain is using a simple random length of RG316 (PTFE)
cable terminated in sma (instrument end) at one end and bare wires the other
(DUT end).

If we want to normalize the cable effect of of the system we do the following:

Do our Open cal with the cable wire ends literally open.
Then solder them shorted and cal Short.
Using a small SMT 50 ohm resistor between the ends of the wires we do cal-50.

If we are doing an S21 measurement then the other cable is prepped similarly
and we do isolation (open) and then connect the ends and perform though.

At this point the plane (interface to the DUT) of measurement is the ends
of those wires.

That would be suitable for a test set up that is literally connected to the end
of the wires like measuring the feed point of a 432mhz dipole.

Jigs are set up the same way save for the measurement point in the
jig gets treated with open/short/load in what ever form is handy.
It helps if the jig is built to help maintain a R50 interface to the DUT.

In all cases at lower HF the wire leads are less critical than at UHF.
Ideally you would like to keep the leads under lamda/200 in length.
Example at 100mhz that 3M, or about .015m=about .5". At 1000mhz
That would be best to stay under .05".

If you are dead ended for some reason and the plane is before the point
of measurement then with good data collection it can be calculated.
That is tedious but there are tools for that. Its a rare case you cannot
get a calibration to the point of the plane (interface to) the unknown
device or termination.

I've worked this way using PNAs to 6ghz and a few times to 60ghz
and often the resulting answer is more than sufficient. Especially for
antennas and their matching networks.

One last thing, in a lot of case carrying the measurement to more
than 3 maybe 4 places is sufficient. After all most parts are barely 5%.

Allison
-----------------
I do not accept private email due to forum scraping groups.io

-----------------
I do not accept private email due to forum scraping groups.io

I have two NanoVNAs here that both seem to have the same problem in that they very often don't power on.

The first NanoVNA is a white/gecko model (2 traces firmware, micro-USB, official ttrftech branded). It didn't come with a battery installed, so I ordered a 500mAh and soldered it to the + and - battery solder points on the pcb.

The second NanoVNA was purchased of eBay a couple of weeks ago (probably a clone) and is black with a USB-C connector and has no identifiable manufacturer's markings on it but it did come with a battery installed.

The batteries in both units have what seems to be a small integrated control circuit underneath some yellow kapton tape.

When I plug in a USB cable to charge the battery they just begin blinking the onboard LED slowly until the battery is full (and the blinking turns into a solid-on). I then unplug the USB cable and let the unit sit there for a few minutes until the LED turns off.

When I now move the switch into the ON position, nothing happens. This is the case for both models.

Here comes the weird part. When I briefly insert and unplug the USB cable so that the unit's LED comes solid-on for a while the unit DOES switch on. I can repeat this several times and it always works. The white/gecko NanoVNA doesn't even switch on when it's charging the battery.

The batteries in both units seem ok; I've tested them for an hour of continuous operation and they didn't run out of juice.

I've read some posts in this forum on installing a silicon diode for battery sensing, none of the units have this diode installed, but I don't think that matters. The firmware on both also doesn't show a battery indicator.

I'm a bit lost as to how to tackle this issue. The only thing I can think of is that maybe the integrated battery protection board causes a slight voltage drop that causes the on-board voltage regulator to trip up, but I have no substantial evidence for that.

Anyone else seen this behavior? Any idea as to what might be the cause and possible fix for this?

Marcel
VK2CEL

how complicated a "test fixture" could I employ before I degrade measurement
accuracy beyond any useful point

VNA works by measuring signals, then calculating based on differences from known references
namely open, short and 50 Ohms. So long as there are measurable differences among those references,
then measurements can be of interest.

To anticipate how interesting, watch the Smith plot while performing calibration with whatever "test fixture".
So long as point clusters for open, short and 50 Ohm are substantially separated,
then there is hope.

I've been looking through posts here, and other internet references, to try to understand the meaning of the term "measurement reference plane." My general understanding is that this refers to the place in a network (and once you attach your VNA, it, and the cables you use to attach it, effectively become part of the network), where one conducts the appropriate calibration procedures, which are intended to eliminate (or at least, significantly reduce) errors that are inevitable in the test equipment. Many of the reference materials provided by VNA manufacturers (manuals and such, which may be found on the internet) refer to the measurement being affected by the use of extensions or fixtures that may be added after calibration is completed, and how these may be compensated for without recalibration.

Okay, so far so good. (Please feel free to comment on the validity of the above, or to correct my interpretation.)

What I have been unable to find is any discussion of how much error might be introduced by use of cables, extensions, and/or fixtures that may be employed up to the measurement reference plane. To put it another way, if the purpose of conducting a calibration is to eliminate/reduce errors introduced by the measurement equipment (meaning the VNA itself, and the cables/fixtures used to attach it to the device under test), just how complicated can the "measurement equipment" be, before residual errors, after calibration, become significant?

Suppose I have a network consisting of, say, 3 connected elements, A, B, and C, where A is connected to B, and B is connected to C, like A==B==C. Suppose, further, that, for the purpose of measuring S11, I will be able to connect the s11 port of my VNA directly to element A. I begin by performing a calibration directly at the s11 port - this becomes my measurement reference plane. I then connect s11 directly to element A, and measure the impedance of the network that consists of A==B==C.

Now, I want to measure the impedance of the network without the presence of element A. Presuming I can connect the s11 port directly to element B, all well and good - I simply disconnect element A, connect the s11 port to element B, and bob's your uncle.

But, suppose, for some reason, I cannot connect directly to element B. Could I connect s11 to element A, disconnect elements B==C, perform a calibration at the far side of element A (thus establishing a reference plane there) reconnect elements B==C, and make the measurement? Element A has become, in some respect, a "test fixture" for measurement of a network consisting of B==C. Taking this a step further, could A==B become a "test fixture" for measurement of element C. And just how complicated a "test fixture" could I employ before I degrade measurement accuracy beyond any useful point? (Of course, the notion of what the "useful point" consists of will vary with the person doing the testing.)

On Sun, Dec 22, 2019 at 07:56 PM, Larry Rothman wrote:

Yes, for that narrow range, you will have a set of cal values.The Nanovna
natively scans 101 points and if you narrow the freq range, it will still
scann 101 points in the narrow range so the interpolation between the points
should be better than if the unit needed to interpolate using the 50k to 900M
range over 101 points.?
Clear as mud?

Great question I was also just wondering. And nice to have the answer, thanks Larry.

--
Regards,
Chris

On Tue, Dec 24, 2019 at 09:50 AM, John wrote:

I will have a copy of the magazine shortly and will summarize any findings

John VE3IPS

When you say "I will have a copy", do you mean you were given a photo copy of the article, or you personally made a photo copy of the article? OR, are you saying you paid for the QEX and are expecting to receive it in the mail? I only ask because due to the wealth of information in this entertaining thread, I have learned that it may or may not be legal to make a "copy" of it!!!!

Sorry, I could not resist!!! ;-)))


--
Regards,
Chris

TDR

entilleser@... wrote: ... Correct? And, if so, what would be the most appropriate way to connect the 50 ohm load across the output terminal posts for the "L" portion of the calibration?

Yes, you are correct. At HF, it doesn't much matter how you connect the 50 ohm load. I have two 100 ohm carbon resistors in parallel that measure 50.1 ohms that I connect with alligator clips. For most of your measurements at HF, the inductance or capacitance of the test leads doesn't much matter.

You can calibrate your measurement reference plane at a number of places. You can do your calibration at the SMA terminals of the NanoVNA. You can do your calibration at the ends of coax cables terminated in SO-239 coax connectors as I have. You can do your calibration at the input or output terminals of your balun and I have done that also. Where you do a particular calibration is called the reference plane. If you want to read the impedance at your balun output, then perform your SOL calibration with your Short, Open, and Load connected to the output terminals of your balun. I have done that for my ladder line fed HF antenna system from 3 MHz to 30 MHz. Here's some further information:

[#96] : The Ultimate Criterion for Endless Reliable VNA Comparisons

Hello,
- - - - - - - - - - - - - (c) gin&pez@arg (cc-by-4.0) 2019 : start - - - - - - - - - - -
Allow us, please, to announce that in our SOW we just "found" what it may
be called : The Ultimate Criterion for Endless Reliable Comparisons, always
FACUPOV of course, between any number of any VNAs, the efficiencies of
their hardware or firmware updates, or whatever else we could imagine, and
-most of all- without any need of standards or of the knowledge of their
nominal values, by using that forgotten property of Cross-Ratio * Preservation:
- - - - - - - - - - - - - finish : (c) gin&pez@arg (cc-by-4.0) 2019 - - - - - - - - - - -


* "The cross-ratio had been defined in deep antiquity, possibly already by
Euclid **, and was considered by Pappus, who noted its key invariance
property" :

** [#81] : On the Physical Expression of Two-Port S-Parameters:
8 December 2019 - /g/nanovna-users/message/7962


Sincerely,

gin&pez@arg

:[96#]

This is one of the big advantages of a small, self contained, unit. One
can connect it to a balanced load or coax with little influence from
surroundings ofr connection to a power source. During CAL. and making the
measurement, let the NANOVNA dangle, do not hold on to it as your body will
introduce variables. If you are measuring at HF frequencies, especially on
our lower bands, the introduction of a very small instrument intelligently
connected to the open wire line will have negligible impact on your
ultimate measurements.

To form the connection between the VNA and the open wire transmission, I'd
first find just the right size bare tinned wire that will snugly fit the
center of the s11 SMA connector (CH 0). Then,, make yourself two *very
short* clip leads using the small alligator clips. Clip the wire to one
end of one clip and run the other between the SMA backshell and one side of
your open wire line. Clip the other clip lead that holds the wire in the
center of the SMA connector to the other side of the open wire line. Make
your measurement. Be sure in both calibration and making the measurement
to NOT HOLD the VNA.

Measurements at HF are reasonably accurate with this method. 6-Meters on
upward, not quite so....

Dave - W?LEV

On Sat, Dec 28, 2019 at 1:19 PM entilleser via Groups.Io <entilleser=
[email protected]> wrote:

How would you do it?

I'm thinking that first, I'd need to construct an adapter for the VNA -
sma connector, short length of coax, with clips on the center conductor and
shield to clip to the two sides of the ladder line (but, the quality of the
connection between the clips and the ladder line wires (among other things)
is going to introduce variables, right?)

Second, I should calibrate for the desired frequency range using the
adapter as described above, in order to "calibrate out" as much of the
peculiarities of the measurement system as I can - I would clip my adapter
to my QRP-Labs dummy load for the load part, leave the clips dangling for
the open, and clip them together for the through.

What kind of trouble am I going to be getting myself into?

--

*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*

For sale: Virtually new (2 weeks old) nanoVNA-F from the designer, not a clone. Working fine with VNA-SAVER under WIN7.
$120 INCLUDES SHIPPING. SOLT components included along with the plastic snap case and foam, plastic screen cover.

Dale W4OP

For sale: Virtually new (2 weeks old) nanoVNA-F from the designer, not a clone. Working fine with VNA-SAVER under WIN7.
$120 INCLUDES SHIPPING. SOLT components included along with the plastic snap case and foam, plastic screen cover.

Dale W4OP

Or get one of those prepaid GreenDot Visa cards and just put in enough balance to cover your purchase needs. They supposedly work exactly the same as a regular card, albeit the additional overhead.

On Fri, Dec 27, 2019 at 10:55 PM, <hugen@...> wrote:

.... If you bought from ebay or Amazon, you
can ask the dealer for the hardware version, we have now pasted "HW version:
3.4" on NanoVNA-H rev3.4.

Hi, any chance you could direct us to one of the ebay sellers that already have v3.4? Earlier I sent a message to Maggie inquiring about this but have not yet gotten a response, and not even sure she might have this information. Thank you.