开云体育

Hello David,

I mentioned in a much earlier post, I have no idea what is in the firmware definition for the standards supplied with the nanoVNA. In addition, based on the physical description of the standards provided, i.e. the 50 ohm load a pair of 100 ohm chip resistors soldered in parallel, that they may not represent the state of the art! However, if there were a way to measure and characterize them as a entry to the unit, such as a classification table, that would be helpful,

I did measure their 50 ohm load after an independent 3.5 mm SOLT cal on a hp 8753 VNA and found their load standard at 900 MHz was at best 17 dB return loss. Another measurement of a second independent 50 ohm load from Weinschel on the 8753 at 900 MHz demonstrated a significantly better return loss. However, on the nanoVNA the Weinschel showed the same 17 dB return loss.

Is there an issue here? YES!

I might add, folks who use this instrument should consider obtaining SMA connector savers. It will not be long before the poor SMA connectors on the nanoVNA are tainted.

Alan

And with battery upgrade. My unit doesn't have a built in battery, so I found one, for now works... but pretend to update the connections and the battery itself, this one is a "little" big for the place (24x30x5mm) but should be 20x30x5

73's
Nuno CT1JQJ

no attachements...

On Wed, 3 Jul 2019 at 00:17, dreschel via Groups.Io <dreschel=
[email protected]> wrote:

Some photos of my NanoVNA measuring a "6.5MHz" Butterworth LP

I don’t see any attachments!

Dave, G8WRB
--
Dr. David Kirkby,

On Wed, 3 Jul 2019 at 04:04, <hugen@...> wrote:

Yes, calibration data can only be modified with electrical delay.

What exactly do you mean by that? Are you saying that the firmware has the
ability to allow one to adjust the delay of the calibration standards? If
so that’s good news. Just being able to enter a delay for the standards
will be a vast improvement over having no control whatsoever.

But someone else wrote ideal standards were assumed.

For better accuracy, I customized the shortest and most accurate

calibrations kits possible.

There’s no need to make the shortest calibration standards possible, *IF*
one can enter the delay of the standards.

*The internet is full of people claiming incorrectly the need to have the
shortest possible delays on calibration standards. * If you look at the
delays on professional calibration kits, you will find they are *longer* on
modern high-end kits than they were on obsolete kits!

The obsolete HP/Agilent 85032B type-N calibration kit had delays of



Female Short = 0.000 ps
Female Open = 0.093 ps

Those are the shortest possible delays one can make on female N.

Now if you compare those figures to the current $20,690 high-end 18 GHz
85054B kit, you will find the delays are much longer in the modern kit.



Female short = 27.990 ps
Female open = 22.905 ps

For the lower cost ($2410) 9 GHz 85033F 9 GHz kit, the delays on the female
parts are:



Female Short = 45.995 ps
Female Open = 41.170 ps

*So very approximately, for female N calibration standards:*

Obsolete 6 GHz kit - delays around 0 ps
Current $2410 9 GHz kit - delays around 43 ps
Current $20,690 18 GHz kit - delays around 24 ps

Clearly on female N parts, it’s possible to make delays close to 0, but
Keysight don’t use them.

The same general principle is true for the male N standards, but in that
case it is impossible to make a zero delay. If you check the links I gave
above, you will find the following.

*Very approximately, for male N calibration standards:*

Obsolete 6 GHz kit - delays around 17 ps
Current 9 GHz kit - delays around 43 ps
Current 18 GHz kit - delays around 60 ps

For obsolete HP 3.5 mm kits, the delays were from memory were around 17 ps,
but any of the modern kits (85033E, 85052D or 85052B) all have delays of
about 30 ps.

Naturally, the accuracy of professional

calibration parts cannot be achieved.


That statement is a bit ambiguous.

If you are saying that a high end VNA is best used with a professional
calibration kit, I would agree with you.

However, if the NanoVNA firmware always assumes idealised parts with a
delay of zero, then things would change *dramatically*. One could easily
make more suitable opens and shorts than would would have if one spent
$2410 on an 85032F. Spending even more, buying the $20,690 85054B would
give you even less suitable open and short standards.

The loads from the $20,690 kit would always be the best loads, but of
course it would be crazy to use loads that probably cost $1500 each on a
VNA costing less than $100.

Unfortunately, some clone makers do not understand the role of the

calibration kit, providing a poor quality load to act as a calibration kit,
which can result in worse measurement results.

Yes, clone makers often don’t appreciate or care what crap they turn out.
But a lot of self-proclaimed experts, writing web pages about how to make
calibration kits don’t understand what they are doing.

My own company, Kirkby Microwave, does care and we have enough knowledge to
understand most of the intricacies. I cringe at some of the stuff I see
written on the internet about VNA calibration kits.

hugen
gen111.taobao.com

Dr. David Kirkby
Kirkby Microwave Ltd.



<>

--
Dr. David Kirkby,

Yes, calibration data can only be modified with electrical delay. For better accuracy, I customized the shortest and most accurate calibrations kits possible. Naturally, the accuracy of professional calibration parts cannot be achieved. Unfortunately, some clone makers do not understand the role of the calibration kit, providing a poor quality load to act as a calibration kit, which can result in worse measurement results.

hugen
gen111.taobao.com

Hi George,
I scarfed the commands by going through main.c (and a few posts here) and there is some ambiguity on how to format a few of them as well as how executing some might affect others.

If you could verify and/or notate the command list while writing your application, I'm sure others would appreciate it.

Also, there are 3 versions of nanoVNA firmware but no one has released the sources for them (that I can find) and I'm sure there may be new commands or options not listed in the original git repository. For this I'm going to go through the binaries for more info.

Thanks
Larry

Some photos of my NanoVNA measuring a "6.5MHz" Butterworth LP

Hi Larry,

The NanoVNA command listing you posted is all that is needed to communicate with the NanoVNA.

I am writing an article on the NanoVNA as well as writing software to perform all the functions of the NanoVNA Sharp and more. My emphasis is on impedance calculations, checking filters, measuring crystals and equivalent circuit models. I do not care for depending on NET.framework or Python. So my software runs on old/cheap laptops running Win XP. These laptops work well in my lab environment and this low-cost VNA does a good job for me.

Regards,
George

David,

Refer to my initial posting (a few posts back from this one) of the NanoVNA Console command listing as well as the Python sourcecode just mentioned.
That should be more than enough info to figure out how to control and extract data from the device over the USB interface.

Regards,
Larry

Hi David,
The simplest way is to read the Python source code example.
9600 bauds seems to be a right choice for USB communication speed.
Regards,
David, F4HTQ.

This is somewhat prompted by a recent question about PC application function/capabilities.

Is the (USB Communications) messaging between the nanovna unit and the host PC -

1. Documented?
2. Could be documented or reverse engineered (i.e., not encrypted or obfuscated)?

If the messaging is or can be documented, that suggests some new capabilities such as headless/scripted operation in a linux host environment (something I could make use of.)

Thanks,

Dave

NOTE:
I created this list by reviewing the older Github source code.
This is the first iteration and there WILL be mistakes - but it's a starting point for the documentation of the console commands.

Please keep this thread on topic!
I will edit this list as users inform me of changes.

Please feel free to change/add/correct/comment and use this list to further the usefulness of the NanoVNA.

Cheers,
Larry

NanoVNA Console Commands:
=========================
help – prints most of the following commands (below) – some are not enabled but appear in the source code
exit – exits and then restarts console mode and prints command prompt
info – prints firmware info:
Kernel: 4.0.0
Compiler: GCC 5.4.1 20160919
Architecture: ARMv6-M
Core Variant: Cortex-M0
Port Info: Preemption through NMI
Platform: STM32F072xB Entry Level Medium Density devices
Board: NanoVNA
Build time: May 5 2019 - 08:54:38
echo - Usage: echo "message"
systime – outputs binary time from 1/1/1980: eg: 81225068
threads
reset - Performing reset
freq - frequency(Hz)}
offset - frequency offset(Hz)}
time – get the time in: timespec.year+1980, timespec.month, timespec.day, timespec.millisecond
dac - usage: dac {value(0-4095)}
saveconfig - saves current configuration - and prints "Config saved".
not sure what in total it saves - need to go through source code.
clearconfig - usage: clearconfig {protection key}
where key is predefined as “1234”
and wrong input gives: “Key unmatched” error.
Correct key gives: “Config and all cal data cleared”
data - usage: data [array]
dump - (if enabled) outputs dump buffer
gamma – Prints gamma[0]& gamma[1]
frequencies – prints a long list of all the sweep points from start to stop
port – Sets port of DSP tlv320aic3204
usage: port {0:TX 1:RX}
stat – outputs processor status:
average: -138 -137
rms: 3597 8
callback count: 9126700
awd: 27
gain – sets gain of DSP tlv320aic3204
usage: gain {lgain(0-95)} [rgain(0-95)]
power - usage: power {0-3}
sweep - usage: sweep {start(Hz)} [stop] [points]
if no inputs: then prints current setup eg:300000000 500000000 101
otherwise, can force new sweep settings using the following commands:
start
stop
center
span
cw
set – sets sweep points
start
stop
test – unknown how to use – appears to set freq span from 10MHz to 90MHz and involves one of the LEDs and touchscreen input
touchcal – produces calibration touch points in the upper left and lower right corners
outputs: "first touch upper left, then lower right...")
"诲辞苍别”
"touch cal params: A B C D (upper left and lower right x-y co-ords)
touchtest – test touch accuracy – touch, hold and drag pointer
pause – pause LCD display output
resume – resume LCD display output
cal - usage: cal [load|open|short|thru|isoln|done|reset|on|off|in]
save - save {id} where ‘id’ is from 0 to 4
recall - recall {id} where ‘id’ is from 0 to 4
trace – prints status of either 2 or 4 traces depending on F/W version used:
0 SWR CH0 1.000000000 0.000000000
1 LOGMAG CH1 1.000000000 7.000000000
2 SMITH CH0 1.000000000 0.000000000
3 PHASE CH1 1.000000000 4.000000000
marker – Usage: marker [n] [off|{index}]
edelay – electrical delay in picoseconds

Dave, as far as I can tell to this point, there is no ability to enter your own polynomial coefficient of the standards. The unit comes with SOL 3.5 mm and they are described as fairly simple construction. Using independent calibration of a 3.5 mm cal kit on another VNA, I determined the quality of their standards. And based on that response I believe for HF applications the unit is quite acceptable.

Again, my earlier question are the standards they provide described within the firmware, don't know. My initial guess is they are taken as ideal, but I may be wrong. Alan

________________________________
From: [email protected] <[email protected]> on behalf of Dr. David Kirkby from Kirkby Microwave Ltd <drkirkby@...>
Sent: Tuesday, July 2, 2019 12:06 PM
To: nanovna-users
Subject: [nanovna-users] Calibration coefficients - can one change them?

I've got nanoVNA on order, but don't have it yet. It's not due to at least
4th July, so that's no big surprise.

Can anyone tell me if one can change the coefficients of the
open/short/load kit? I just have done a test with 4 sorts of opens. The
connector was a male N, so the calibration standard a female N. But
anyway, here are the results at 902.625 MHz, which is the nearest frequency
I have any data. (I had calibrated to 18 GHz for another job, so don't have
data at exactly 900 MHz, but this is as close as makes no practical
difference)


*Male N plug just open. No female standard*. Phase = +4.64722 degrees @
902.62500
Female open standard from HP 85032B open standard, used without any
extender, as it is NOT supposed to be. Phase = +4.64014 degrees @ 902.62500
MHz
Female open standard from HP 85032B calibration kit, with the extender, as
it SHOULD be used -3.65161 degrees @ 902.62500 MHz
Female Open standard from HP 85054B 18 GHz calibration kit. Phase =
-18.18457 @ 902.62500 MHz

IMPORTANT
The male N plug was a metrology grade male-male adapter from an HP 85054B
VNA calibration kit. Since the shape of the male pin is not well defined,
and commercial grade connectors are recessed by various amounts, I would
not expect this result to be reproducible with different connectors, but
fairly substantial variations

Anyway, the conclusion is that for the female N calibration standards, the
phase varies from +4.6 to -18.2 degrees at 902 MHz. So a phase variation of
22.8 degrees depending on what calibration standard one uses. The variation
would be smaller at lower frequencies, but depending on what the nanoVNA
assumes about the calibration standard, one could get quite different
results.

Ideally, one needs to be able to enter the offset delay of the calibration
standards as an *absolute minimum.* The fringe capacitance would be nice
too, but could just about get away without that, as one could do a rough
job of compensation via changing the offset delay. Better still would be a
third order polynomial, which would make entering coefficients from a
commercial calibration kit easy, without trying to work out any
compensation values.

If the firmware is dumb enough to assume the open standard is ideal (phase
= 0 degrees), and the short is ideal (phase = 180 degrees), then it would
cause significant errors.

Likewise, if the firmware made assumptions about the SMA kit supplied,
those assumptions would be wrong if a different SMA, 3.5 mm, N or APC cali
kit was used.

Even if you are not interested in phase measurements, be aware of the fact
the point of the vector correction is to correct for amplitude variations
too. Anyone that believes that they don't need to worry about vector
correction, as they are only interested in amplitude measurements, is
seriously mistaken.

Dave

--
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

I've got nanoVNA on order, but don't have it yet. It's not due to at least
4th July, so that's no big surprise.

Can anyone tell me if one can change the coefficients of the
open/short/load kit? I just have done a test with 4 sorts of opens. The
connector was a male N, so the calibration standard a female N. But
anyway, here are the results at 902.625 MHz, which is the nearest frequency
I have any data. (I had calibrated to 18 GHz for another job, so don't have
data at exactly 900 MHz, but this is as close as makes no practical
difference)


*Male N plug just open. No female standard*. Phase = +4.64722 degrees @
902.62500
Female open standard from HP 85032B open standard, used without any
extender, as it is NOT supposed to be. Phase = +4.64014 degrees @ 902.62500
MHz
Female open standard from HP 85032B calibration kit, with the extender, as
it SHOULD be used -3.65161 degrees @ 902.62500 MHz
Female Open standard from HP 85054B 18 GHz calibration kit. Phase =
-18.18457 @ 902.62500 MHz

IMPORTANT
The male N plug was a metrology grade male-male adapter from an HP 85054B
VNA calibration kit. Since the shape of the male pin is not well defined,
and commercial grade connectors are recessed by various amounts, I would
not expect this result to be reproducible with different connectors, but
fairly substantial variations

Anyway, the conclusion is that for the female N calibration standards, the
phase varies from +4.6 to -18.2 degrees at 902 MHz. So a phase variation of
22.8 degrees depending on what calibration standard one uses. The variation
would be smaller at lower frequencies, but depending on what the nanoVNA
assumes about the calibration standard, one could get quite different
results.

Ideally, one needs to be able to enter the offset delay of the calibration
standards as an *absolute minimum.* The fringe capacitance would be nice
too, but could just about get away without that, as one could do a rough
job of compensation via changing the offset delay. Better still would be a
third order polynomial, which would make entering coefficients from a
commercial calibration kit easy, without trying to work out any
compensation values.

If the firmware is dumb enough to assume the open standard is ideal (phase
= 0 degrees), and the short is ideal (phase = 180 degrees), then it would
cause significant errors.

Likewise, if the firmware made assumptions about the SMA kit supplied,
those assumptions would be wrong if a different SMA, 3.5 mm, N or APC cali
kit was used.

Even if you are not interested in phase measurements, be aware of the fact
the point of the vector correction is to correct for amplitude variations
too. Anyone that believes that they don't need to worry about vector
correction, as they are only interested in amplitude measurements, is
seriously mistaken.

Dave

--
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

Alan,
Thanks for message 83. I will try that this morning. Bill

Thank you! The photos are a great help!
Bill

See message #83. Alan

Bill, I wrote up a calibration sequence in an earlier thread. If you cannot find it, I will cut and paste in a reply. Currently this was done on the 2 -track unit but I assume the sequence is no different for the 4 track.

Key is the flow on the unit has you go to DONE and causes you to omit SHORT and OPEN.

Alan W4AMV

SMA male calibration kit (OPEN / SHORT /LOAD).