开云体育

On Tue, 3 Sep 2019 at 12:18, Warren Allgyer <allgyer@...> wrote:

Roger, I am not trying to demean your efforts. I am just pointing out that
such differences are not significant in the real world not just to me.
There may indeed be real world significant differences but 900 MHz span
noise floor measurements are not going to reveal them.

I have just done a cold, calibrated start of my White Salamander with a
very poor 150 ohm load which is highly reactive at 720 MHz and stored the
results. The return loss is 25 dB. I will recheck in one hour and see what
drift has taken place. Here is the cold startup.



I will publish the other plot in one hour.

WA8TOD



On Sep 2, 2019, at 7:58 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
Not much more to say now, as my results were nonsense and meaningless to
you.
And I won't be running around trying to create scenarios which do mean
something to you.

I have shown my results as they are and for what they are worth. They
showed a difference and that was interesting to me.
I am not trying to prove you wrong, just presenting the facts as I happen
to have two devices to compare.

I also thought it would be an interesting project to try and improve the
white unit, as fundamentally they are not that different.

Roger




On Tue, 3 Sep 2019 at 11:11, Warren Allgyer <allgyer@...> wrote:

Roger

I have seen the article. Return loss measurements of 40 dB or greater

turn

to mush on most instruments that cost less than $10,000. No surprise the
same would apply to the NanoVNA. But a couple of points:

1) Use of the NanoVNA or even calibration at a 900 MHz span is nonsense
and meaningless. No one would use a 900 MHz span for anything.

2) Characterizing the noise floor and the resulting possible dynamic

range

based on such a span is also nonsense. The resolution bandwidth at that
span is 9 MHz! Useful for nothing.

3) Reducing the span to something useful and reasonable will put even

your

White Salamander into spec or very near to it for the 600-900 MHz range.
The general spec is 50 dB of dynamic range from 600-900, 60 dB from
300-600, and 70 dB from 0-300. My White Salamander easily meets that spec
at 720 MHz when the span is reduced to something useful like 5 or even 50
MHz.

Attached is my White Salamander at the full 900 MHz span and with Center
at 720 MHz with a 50 and then a 5 MHz span. Worst case, allowing your
generous 10 dB of margin from the noise floor, it can easily resolve and
display return losses down to -35 dB and that is plenty good enough for
99.9% of the folks here who would use the instrument.

Comparing instruments based on a 900 MHz span noise floor is not very
informative. And no one else, including you, have published comparisons

of

reasonable RL measurements made at reasonable spans and RBW.

WA8TOD

On Sep 2, 2019, at 5:45 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
I don't know if you have seen this before. See the chart labelled
"Reflected Power Measurement Errors for Various Load Return Loss Values"
in this PDF:

In reality the trace we are talking about is the effective directivity of
the device. This is the error corrected directivity and can be compared

to

the directivity of a directional coupler attached to a Spec An or a

Scalar

Network Analyser.
The Vector part of the VNA allows this error correction to improve upon

the

directivity of the bridge which is in the device. Interestingly the real
physical directivity of my white unit is slightly better than the hugen
unit.
It is the stability which is worse.

You can attach an antenna and see a spike down below this 'floor'. There

is

an example of this in one of the online nanovna reviews IIRC.
The reviewer even questions it and says something like 'it shouldn't be
able to measure that'. It sounded to me that he didn't realise that the
error can go in both directions either. I can't find that review it at

the

moment though.

I agree with you, in that if the effective directivity is 30dB, you can
measure down to 20dB plus or minus about 3dB - so your measurement is
within 6dB of whatever it really is.
If that is all you need, then that is fine. Absolutely no issue.

Anyway, I did a couple more tests - one up to 6MHz to shine a light on

the

low freq performance.
The other was full span.
See the bottom of the page:

The full span test shows them about the same.
The low freq test shows an obvious difference between the units. The

hugen

units looks incredibly good here. Maybe I have done something wrong!
Whether it is material to you Warren, or anyone else, is not for me to
decide. I don't know what you want to use it for. For me, they are about
the same price. I know which one I would rather have.

Before these tests, I did wrap some aluminum tape around both units.

There

are still plenty of holes to let the heat out - Its pretty rough - I'm

not

a surgeon - and it took about 2 minutes to do.
I can't say if the tape made any difference though.

Its not worth me spending any more time on this. Hopefully someone else

can

pick this up and let us know if blocking up the sides, or putting it in a
bigger box as mentioned by Jerry, does help or not.

Roger.

On Sep 2, 2019, at 8:18 PM, Warren Allgyer via Groups.Io <allgyer@...> wrote:

Roger, I am not trying to demean your efforts. I am just pointing out that such differences are not significant in the real world not just to me. There may indeed be real world significant differences but 900 MHz span noise floor measurements are not going to reveal them.

I have just done a cold, calibrated start of my White Salamander with a very poor 150 ohm load which is highly reactive at 720 MHz and stored the results. The return loss is 25 dB. I will recheck in one hour and see what drift has taken place. Here is the cold startup.



I will publish the other plot in one hour.

WA8TOD



On Sep 2, 2019, at 7:58 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
Not much more to say now, as my results were nonsense and meaningless to
you.
And I won't be running around trying to create scenarios which do mean
something to you.

I have shown my results as they are and for what they are worth. They
showed a difference and that was interesting to me.
I am not trying to prove you wrong, just presenting the facts as I happen
to have two devices to compare.

I also thought it would be an interesting project to try and improve the
white unit, as fundamentally they are not that different.

Roger




On Tue, 3 Sep 2019 at 11:11, Warren Allgyer <allgyer@...> wrote:

Roger

I have seen the article. Return loss measurements of 40 dB or greater turn
to mush on most instruments that cost less than $10,000. No surprise the
same would apply to the NanoVNA. But a couple of points:

1) Use of the NanoVNA or even calibration at a 900 MHz span is nonsense
and meaningless. No one would use a 900 MHz span for anything.

2) Characterizing the noise floor and the resulting possible dynamic range
based on such a span is also nonsense. The resolution bandwidth at that
span is 9 MHz! Useful for nothing.

3) Reducing the span to something useful and reasonable will put even your
White Salamander into spec or very near to it for the 600-900 MHz range.
The general spec is 50 dB of dynamic range from 600-900, 60 dB from
300-600, and 70 dB from 0-300. My White Salamander easily meets that spec
at 720 MHz when the span is reduced to something useful like 5 or even 50
MHz.

Attached is my White Salamander at the full 900 MHz span and with Center
at 720 MHz with a 50 and then a 5 MHz span. Worst case, allowing your
generous 10 dB of margin from the noise floor, it can easily resolve and
display return losses down to -35 dB and that is plenty good enough for
99.9% of the folks here who would use the instrument.

Comparing instruments based on a 900 MHz span noise floor is not very
informative. And no one else, including you, have published comparisons of
reasonable RL measurements made at reasonable spans and RBW.

WA8TOD

On Sep 2, 2019, at 5:45 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
I don't know if you have seen this before. See the chart labelled
"Reflected Power Measurement Errors for Various Load Return Loss Values"
in this PDF:




In reality the trace we are talking about is the effective directivity of
the device. This is the error corrected directivity and can be compared to
the directivity of a directional coupler attached to a Spec An or a Scalar
Network Analyser.
The Vector part of the VNA allows this error correction to improve upon the
directivity of the bridge which is in the device. Interestingly the real
physical directivity of my white unit is slightly better than the hugen
unit.
It is the stability which is worse.

You can attach an antenna and see a spike down below this 'floor'. There is
an example of this in one of the online nanovna reviews IIRC.
The reviewer even questions it and says something like 'it shouldn't be
able to measure that'. It sounded to me that he didn't realise that the
error can go in both directions either. I can't find that review it at the
moment though.

I agree with you, in that if the effective directivity is 30dB, you can
measure down to 20dB plus or minus about 3dB - so your measurement is
within 6dB of whatever it really is.
If that is all you need, then that is fine. Absolutely no issue.

Anyway, I did a couple more tests - one up to 6MHz to shine a light on the
low freq performance.
The other was full span.
See the bottom of the page:




The full span test shows them about the same.
The low freq test shows an obvious difference between the units. The hugen
units looks incredibly good here. Maybe I have done something wrong!
Whether it is material to you Warren, or anyone else, is not for me to
decide. I don't know what you want to use it for. For me, they are about
the same price. I know which one I would rather have.

Before these tests, I did wrap some aluminum tape around both units. There
are still plenty of holes to let the heat out - Its pretty rough - I'm not
a surgeon - and it took about 2 minutes to do.
I can't say if the tape made any difference though.

Its not worth me spending any more time on this. Hopefully someone else can
pick this up and let us know if blocking up the sides, or putting it in a
bigger box as mentioned by Jerry, does help or not.

Roger.

<PastedGraphic-1.png>

On Sep 2, 2019, at 7:58 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
Not much more to say now, as my results were nonsense and meaningless to
you.
And I won't be running around trying to create scenarios which do mean
something to you.

I have shown my results as they are and for what they are worth. They
showed a difference and that was interesting to me.
I am not trying to prove you wrong, just presenting the facts as I happen
to have two devices to compare.

I also thought it would be an interesting project to try and improve the
white unit, as fundamentally they are not that different.

Roger




On Tue, 3 Sep 2019 at 11:11, Warren Allgyer <allgyer@...> wrote:

Roger

I have seen the article. Return loss measurements of 40 dB or greater turn
to mush on most instruments that cost less than $10,000. No surprise the
same would apply to the NanoVNA. But a couple of points:

1) Use of the NanoVNA or even calibration at a 900 MHz span is nonsense
and meaningless. No one would use a 900 MHz span for anything.

2) Characterizing the noise floor and the resulting possible dynamic range
based on such a span is also nonsense. The resolution bandwidth at that
span is 9 MHz! Useful for nothing.

3) Reducing the span to something useful and reasonable will put even your
White Salamander into spec or very near to it for the 600-900 MHz range.
The general spec is 50 dB of dynamic range from 600-900, 60 dB from
300-600, and 70 dB from 0-300. My White Salamander easily meets that spec
at 720 MHz when the span is reduced to something useful like 5 or even 50
MHz.

Attached is my White Salamander at the full 900 MHz span and with Center
at 720 MHz with a 50 and then a 5 MHz span. Worst case, allowing your
generous 10 dB of margin from the noise floor, it can easily resolve and
display return losses down to -35 dB and that is plenty good enough for
99.9% of the folks here who would use the instrument.

Comparing instruments based on a 900 MHz span noise floor is not very
informative. And no one else, including you, have published comparisons of
reasonable RL measurements made at reasonable spans and RBW.

WA8TOD

On Sep 2, 2019, at 5:45 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
I don't know if you have seen this before. See the chart labelled
"Reflected Power Measurement Errors for Various Load Return Loss Values"
in this PDF:




In reality the trace we are talking about is the effective directivity of
the device. This is the error corrected directivity and can be compared to
the directivity of a directional coupler attached to a Spec An or a Scalar
Network Analyser.
The Vector part of the VNA allows this error correction to improve upon the
directivity of the bridge which is in the device. Interestingly the real
physical directivity of my white unit is slightly better than the hugen
unit.
It is the stability which is worse.

You can attach an antenna and see a spike down below this 'floor'. There is
an example of this in one of the online nanovna reviews IIRC.
The reviewer even questions it and says something like 'it shouldn't be
able to measure that'. It sounded to me that he didn't realise that the
error can go in both directions either. I can't find that review it at the
moment though.

I agree with you, in that if the effective directivity is 30dB, you can
measure down to 20dB plus or minus about 3dB - so your measurement is
within 6dB of whatever it really is.
If that is all you need, then that is fine. Absolutely no issue.

Anyway, I did a couple more tests - one up to 6MHz to shine a light on the
low freq performance.
The other was full span.
See the bottom of the page:




The full span test shows them about the same.
The low freq test shows an obvious difference between the units. The hugen
units looks incredibly good here. Maybe I have done something wrong!
Whether it is material to you Warren, or anyone else, is not for me to
decide. I don't know what you want to use it for. For me, they are about
the same price. I know which one I would rather have.

Before these tests, I did wrap some aluminum tape around both units. There
are still plenty of holes to let the heat out - Its pretty rough - I'm not
a surgeon - and it took about 2 minutes to do.
I can't say if the tape made any difference though.

Its not worth me spending any more time on this. Hopefully someone else can
pick this up and let us know if blocking up the sides, or putting it in a
bigger box as mentioned by Jerry, does help or not.

Roger.

On Tue, 3 Sep 2019 at 11:11, Warren Allgyer <allgyer@...> wrote:

Roger

I have seen the article. Return loss measurements of 40 dB or greater turn
to mush on most instruments that cost less than $10,000. No surprise the
same would apply to the NanoVNA. But a couple of points:

1) Use of the NanoVNA or even calibration at a 900 MHz span is nonsense
and meaningless. No one would use a 900 MHz span for anything.

2) Characterizing the noise floor and the resulting possible dynamic range
based on such a span is also nonsense. The resolution bandwidth at that
span is 9 MHz! Useful for nothing.

3) Reducing the span to something useful and reasonable will put even your
White Salamander into spec or very near to it for the 600-900 MHz range.
The general spec is 50 dB of dynamic range from 600-900, 60 dB from
300-600, and 70 dB from 0-300. My White Salamander easily meets that spec
at 720 MHz when the span is reduced to something useful like 5 or even 50
MHz.

Attached is my White Salamander at the full 900 MHz span and with Center
at 720 MHz with a 50 and then a 5 MHz span. Worst case, allowing your
generous 10 dB of margin from the noise floor, it can easily resolve and
display return losses down to -35 dB and that is plenty good enough for
99.9% of the folks here who would use the instrument.

Comparing instruments based on a 900 MHz span noise floor is not very
informative. And no one else, including you, have published comparisons of
reasonable RL measurements made at reasonable spans and RBW.

WA8TOD

On Sep 2, 2019, at 5:45 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
I don't know if you have seen this before. See the chart labelled
"Reflected Power Measurement Errors for Various Load Return Loss Values"
in this PDF:




In reality the trace we are talking about is the effective directivity of
the device. This is the error corrected directivity and can be compared to
the directivity of a directional coupler attached to a Spec An or a Scalar
Network Analyser.
The Vector part of the VNA allows this error correction to improve upon the
directivity of the bridge which is in the device. Interestingly the real
physical directivity of my white unit is slightly better than the hugen
unit.
It is the stability which is worse.

You can attach an antenna and see a spike down below this 'floor'. There is
an example of this in one of the online nanovna reviews IIRC.
The reviewer even questions it and says something like 'it shouldn't be
able to measure that'. It sounded to me that he didn't realise that the
error can go in both directions either. I can't find that review it at the
moment though.

I agree with you, in that if the effective directivity is 30dB, you can
measure down to 20dB plus or minus about 3dB - so your measurement is
within 6dB of whatever it really is.
If that is all you need, then that is fine. Absolutely no issue.

Anyway, I did a couple more tests - one up to 6MHz to shine a light on the
low freq performance.
The other was full span.
See the bottom of the page:




The full span test shows them about the same.
The low freq test shows an obvious difference between the units. The hugen
units looks incredibly good here. Maybe I have done something wrong!
Whether it is material to you Warren, or anyone else, is not for me to
decide. I don't know what you want to use it for. For me, they are about
the same price. I know which one I would rather have.

Before these tests, I did wrap some aluminum tape around both units. There
are still plenty of holes to let the heat out - Its pretty rough - I'm not
a surgeon - and it took about 2 minutes to do.
I can't say if the tape made any difference though.

Its not worth me spending any more time on this. Hopefully someone else can
pick this up and let us know if blocking up the sides, or putting it in a
bigger box as mentioned by Jerry, does help or not.

Roger.

-----Original Message-----
From: Larry Rothman <ac293@...>
To: nanovna-users <[email protected]>
Sent: Mon, Sep 2, 2019 4:02 pm
Subject: Re: [nanovna-users] Excellent VNA tutorial links

Stuart, there are garbage chars at the end of the first link....

The requested URL /HamRadio/HamRadio_DG8SAQ_2018_English.pdf?? was not found on this server.

On Sep 2, 2019, at 5:45 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
I don't know if you have seen this before. See the chart labelled
"Reflected Power Measurement Errors for Various Load Return Loss Values"
in this PDF:



In reality the trace we are talking about is the effective directivity of
the device. This is the error corrected directivity and can be compared to
the directivity of a directional coupler attached to a Spec An or a Scalar
Network Analyser.
The Vector part of the VNA allows this error correction to improve upon the
directivity of the bridge which is in the device. Interestingly the real
physical directivity of my white unit is slightly better than the hugen
unit.
It is the stability which is worse.

You can attach an antenna and see a spike down below this 'floor'. There is
an example of this in one of the online nanovna reviews IIRC.
The reviewer even questions it and says something like 'it shouldn't be
able to measure that'. It sounded to me that he didn't realise that the
error can go in both directions either. I can't find that review it at the
moment though.

I agree with you, in that if the effective directivity is 30dB, you can
measure down to 20dB plus or minus about 3dB - so your measurement is
within 6dB of whatever it really is.
If that is all you need, then that is fine. Absolutely no issue.

Anyway, I did a couple more tests - one up to 6MHz to shine a light on the
low freq performance.
The other was full span.
See the bottom of the page:



The full span test shows them about the same.
The low freq test shows an obvious difference between the units. The hugen
units looks incredibly good here. Maybe I have done something wrong!
Whether it is material to you Warren, or anyone else, is not for me to
decide. I don't know what you want to use it for. For me, they are about
the same price. I know which one I would rather have.

Before these tests, I did wrap some aluminum tape around both units. There
are still plenty of holes to let the heat out - Its pretty rough - I'm not
a surgeon - and it took about 2 minutes to do.
I can't say if the tape made any difference though.

Its not worth me spending any more time on this. Hopefully someone else can
pick this up and let us know if blocking up the sides, or putting it in a
bigger box as mentioned by Jerry, does help or not.

Roger.

On Tue, 3 Sep 2019 at 08:20, Warren Allgyer <allgyer@...> wrote:

I am going to beg to differ Roger.

The only material difference in the floor ( I will continue to
characterize it a a “noise floor” because it has the randomness of noise
and if it is not noise then I don’t know what it is…) is on immediate turn
on with immediate calibration. That would be in your first chart. In the
others I see no material difference.

I don’t think you will see a ‘dip’ below the noise floor….. the noise
floor is there as the limit of the calibration and nothing will be
displayed below that point by definition.

The reason the trace is higher at upper frequencies is because the NanoVNA
switches from fundamental to third harmonic at 300 MHz. While the
fundamental level is boosted at that point by about 12 dB, the actual
excitation continues to fall off for the third harmonic as the frequency
increases. When calibrated the process compensates for the lower level by
raising the calibration constant to bring the calibrated level for each bin
up to the reference. That brings up the noise floor and reduces dynamic
range.

In all cases except for the first “immediate turn on” chart there is at
least 10 dB of margin between -30 dB and the noise…… and anyone who expects
accurate return loss measurements greater than 30 dB for such a device,
Hugen-made or not, is just kidding themselves. Yes, it will give you a
number but it is not accurate and not repeatable.

But all of that discussion is not material because the “noise floor” or
“calibration limit” or whatever you wish to call the hash at the bottom of
the screen has no effect on accuracy or repeatability at any level higher
than floor +10 dB.

Yes, of course one must calibrate most devices immediately before making
critical measurements. However, absolute values are in most cases not
necessary or even useful. When used as an antenna analyzer the objective is
the lowest VSWR/highest return loss at the desired frequency. When
characterizing or tuning a filter in S21 mode the shape, flatness, and
skirt steepness are optimized. Neither of those requires an absolute value
with 0.01 dB accuracy.

Try the test I recommended and then show us the results.

WA8TOD


On Sep 2, 2019, at 4:00 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
There are a couple of real world takeaways from the measurements I think.

One point is that the trace is not anywhere near 60dB at all freqs. It is
only around 25dB RL on the white unit at the highest end in the first test.
To measure RL with a degree of confidence we need about 10dB of 'headroom'.
So that allows you to measure down to maybe 15dB with a few dB if error.
Errors in RL measurements are huge if you get close to the effective
directivity limit of the vna.
If you tried to measure a 20dB RL device then the actual result could be
anywhere in a 10 or 12dB range.

It does not behave a spectrum analyzer and this is not a noise floor. An
antenna measurement for example will often show a dip in the trace well
below this 'accuracy floor'.
That measurement will be rubbish and I will eat my hat if most people don't
fall for it.

The second point is that saved calibrations are pointless if the device
drifts all over the place after calibrating.

The white device drifts more and so for more confidence in that higher
range, it needs to be powered on 'for a while', then a cal done, then the
measurement taken.
That is the same procedure you use for a lab VNA.
The hugen device could be turned on, and a measurement taken right away
using a saved cal.
That procedure matches how you use any other antenna analyser.

Both of the above points are relevant to the simple 'antenna analyzer' use
case. Which is turn it on, attach it to the feedline, and take the
measurement.
The worse the accuracy is then the more expert you need to be to make use
of the device.

I have added the open port tests. After doing a calibration and leaving
overnight the white unit has drifted away from 0dB much more than the hugen
device.
This lends more weight to the above comment - the white unit should be
calibrated immediately before any use.

The bottom line is that I see clear differences between the different units
I have at least.

Roger

[image: image.png]

On Tue, 3 Sep 2019, 5:35 AM Warren Allgyer, <allgyer@...> wrote:

Roger

I am reviewing your comparison results on my phone so I may have missed
something.

What I see is comparisons of the S11 noise floor in the 60-70 dB range
return loss. This is meaningless in the real world for all but the most
critical applications, like comparing the return loss of an N connector
versus an SMA for the example.

A return loss of 30dB equals a VSWR of 1.06:1. A return loss of 40 dB
equals a VSWR of 1.02:1 and is exponentially more difficult to achieve

and

measure accurately. For all but the most critical lab measurements return
loss values greater than 30 dB are meaningless. They are also much more
sensitive to calibration errors.

Comparisons of noise floor are interesting and do indeed likely reflect
more care, shielding, and execution against a design. They do not,

however,

represent an indication of comparative measurement accuracy at usable
return loss values.

The comparison you could do to measure real world comparative performance
would be to use a 100-500 ohm resistor and measure return loss and other
parameters at, say, 50, 450, and 850 MHz. I will eat my hat if you find
more than 1 dB of difference between the units and I expect it will be

far

less than that. I do not have a Hugen unit but the variance between my
worse and worst units for these tests is less than 0.3 dB. NOTE: all

units

being compared must have been carefully calibrated using the same set of
OSLIT loads!

In summary, a difference in noise floor between 60 and 70 dB is
meaningless in the real world and has no bearing on the accuracy of the
instrument for normal ranges of use.

WA8TOD

On Sep 2, 2019, at 8:57 AM, Roger Henderson <hendorog@...> wrote:

I have posted some comparisons here between my white 'Gecko/Salamander'
device and my hugen unit:

In all these traces, the lower the trace, the better. If the device is
theoretically perfect then the trace will be at some ridiculously low

value

as it will ultimately be limited by the mathematical precision in the
calculations.
This is what happens if I save measurements and transfer them to a PC,

do a

calibration and then apply the error correction to the load.
Since these are real physical devices, and they drift around so each

sweep

will be slightly different - even when measuring the same load and not
touching anything.
So perfection doesn't happen, and the trace will slowly float upwards as
the device shows its limitations.

First test file was saved after calibrating both devices right after

power

on.
Second test file was saved after leaving them both on for an hour and

then

calibrating.
Tests 3, 4 and 5 were saved after increasing lengths of time.

There is a clear advantage in the hugen trace after each of the
calibrations.
Over time the two traces eventually come together.

The white unit is quite poor at 900MHz unless it has a good amount of

warm

up time.
The white unit is much worse at the very lowest frequencies in the

trace,

and note that it had a Start freq of 1MHz. This was my mistake as the

hugen

unit was starting at 50kHz.

The other test I should do is to see how quickly the trace drifts away
from 0dB - after calibration and with the test port open.
I know the white unit is worse there too, just from informally testing

it,

but it would be good to do it properly.

Also, it seems logical, well to me at least, that sealing up the sides

to

limit air currents will improve these stability type results on both
devices. I haven't tried that though.

Roger

On Mon, 2 Sep 2019 at 19:18, Warren Allgyer <allgyer@...> wrote:

Hugen

With all due respect, the thread you cite says clearly there is no
operational difference among the fully shielded, "better" versions, the
"worse" clones, and the worst. No one has presented operational data

that

distinguishes clone performance at any level. The thread actually says
slightly better performance was had from unshielded clones.

The images presented on the data comparison are indeed cut-and-paste
images from advertisements but they are identical to the actual VNAs in

my

possession. I have posted an actual picture of my units as well so you

can

see the images used for identification are identical.

The data I have published shows no significant difference between the

two

clones.

So let's review:

1) No one, including you, have published any data or test results
demonstrating a significant performance advantage for the "real" unit
versus the clones.

2) No one, including you and me, has been able to publish data showing

a

significant performance difference among the clones.

3) I have stated but not published data (I am happy to do so) where I
compared the results of my two clones to a spectrum analyzer/tracking
generator/RF bridge combination and found no significant variance in
results among all three devices.

The qualities of the original versus the clones...... so far..... have
been distinctions without differences. Those differences have been

cosmetic

only and no one has shown a resulting measurement discrepancy.

I challenge you or anyone on this board to publish actual data showing
that a clone performs significantly worse than an "original". I don't

think

that has been done. The thread you cite certainly does not support

measured

differences. If you have data please show it. If not then I think we

all

need to stop confusing the readers here. Some people have actually

returned

what are likely perfectly good devices because of cosmetics.

WA8TOD

<image.png>

On Mon, 2 Sep 2019 at 22:50, <erik@...> wrote:

I'm using the NanoVNA in combination with windows 10
The driver gets installed but any application trying to open the serial
over USB port hangs
Is there anything I am supposed to do/change?
Any help is appriciated

On Sep 2, 2019, at 4:00 PM, Roger Henderson <hendorog@...> wrote:

Hi Warren,
There are a couple of real world takeaways from the measurements I think.

One point is that the trace is not anywhere near 60dB at all freqs. It is
only around 25dB RL on the white unit at the highest end in the first test.
To measure RL with a degree of confidence we need about 10dB of 'headroom'.
So that allows you to measure down to maybe 15dB with a few dB if error.
Errors in RL measurements are huge if you get close to the effective
directivity limit of the vna.
If you tried to measure a 20dB RL device then the actual result could be
anywhere in a 10 or 12dB range.

It does not behave a spectrum analyzer and this is not a noise floor. An
antenna measurement for example will often show a dip in the trace well
below this 'accuracy floor'.
That measurement will be rubbish and I will eat my hat if most people don't
fall for it.

The second point is that saved calibrations are pointless if the device
drifts all over the place after calibrating.

The white device drifts more and so for more confidence in that higher
range, it needs to be powered on 'for a while', then a cal done, then the
measurement taken.
That is the same procedure you use for a lab VNA.
The hugen device could be turned on, and a measurement taken right away
using a saved cal.
That procedure matches how you use any other antenna analyser.

Both of the above points are relevant to the simple 'antenna analyzer' use
case. Which is turn it on, attach it to the feedline, and take the
measurement.
The worse the accuracy is then the more expert you need to be to make use
of the device.

I have added the open port tests. After doing a calibration and leaving
overnight the white unit has drifted away from 0dB much more than the hugen
device.
This lends more weight to the above comment - the white unit should be
calibrated immediately before any use.

The bottom line is that I see clear differences between the different units
I have at least.

Roger

[image: image.png]

On Tue, 3 Sep 2019, 5:35 AM Warren Allgyer, <allgyer@...> wrote:

Roger

I am reviewing your comparison results on my phone so I may have missed
something.

What I see is comparisons of the S11 noise floor in the 60-70 dB range
return loss. This is meaningless in the real world for all but the most
critical applications, like comparing the return loss of an N connector
versus an SMA for the example.

A return loss of 30dB equals a VSWR of 1.06:1. A return loss of 40 dB
equals a VSWR of 1.02:1 and is exponentially more difficult to achieve and
measure accurately. For all but the most critical lab measurements return
loss values greater than 30 dB are meaningless. They are also much more
sensitive to calibration errors.

Comparisons of noise floor are interesting and do indeed likely reflect
more care, shielding, and execution against a design. They do not, however,
represent an indication of comparative measurement accuracy at usable
return loss values.

The comparison you could do to measure real world comparative performance
would be to use a 100-500 ohm resistor and measure return loss and other
parameters at, say, 50, 450, and 850 MHz. I will eat my hat if you find
more than 1 dB of difference between the units and I expect it will be far
less than that. I do not have a Hugen unit but the variance between my
worse and worst units for these tests is less than 0.3 dB. NOTE: all units
being compared must have been carefully calibrated using the same set of
OSLIT loads!

In summary, a difference in noise floor between 60 and 70 dB is
meaningless in the real world and has no bearing on the accuracy of the
instrument for normal ranges of use.

WA8TOD

On Sep 2, 2019, at 8:57 AM, Roger Henderson <hendorog@...> wrote:

I have posted some comparisons here between my white 'Gecko/Salamander'
device and my hugen unit:

In all these traces, the lower the trace, the better. If the device is
theoretically perfect then the trace will be at some ridiculously low

value

as it will ultimately be limited by the mathematical precision in the
calculations.
This is what happens if I save measurements and transfer them to a PC,

do a

calibration and then apply the error correction to the load.
Since these are real physical devices, and they drift around so each

sweep

will be slightly different - even when measuring the same load and not
touching anything.
So perfection doesn't happen, and the trace will slowly float upwards as
the device shows its limitations.

First test file was saved after calibrating both devices right after

power

on.
Second test file was saved after leaving them both on for an hour and

then

calibrating.
Tests 3, 4 and 5 were saved after increasing lengths of time.

There is a clear advantage in the hugen trace after each of the
calibrations.
Over time the two traces eventually come together.

The white unit is quite poor at 900MHz unless it has a good amount of

warm

up time.
The white unit is much worse at the very lowest frequencies in the trace,
and note that it had a Start freq of 1MHz. This was my mistake as the

hugen

unit was starting at 50kHz.

The other test I should do is to see how quickly the trace drifts away
from 0dB - after calibration and with the test port open.
I know the white unit is worse there too, just from informally testing

it,

but it would be good to do it properly.

Also, it seems logical, well to me at least, that sealing up the sides to
limit air currents will improve these stability type results on both
devices. I haven't tried that though.

Roger

On Mon, 2 Sep 2019 at 19:18, Warren Allgyer <allgyer@...> wrote:

Hugen

With all due respect, the thread you cite says clearly there is no
operational difference among the fully shielded, "better" versions, the
"worse" clones, and the worst. No one has presented operational data

that

distinguishes clone performance at any level. The thread actually says
slightly better performance was had from unshielded clones.

The images presented on the data comparison are indeed cut-and-paste
images from advertisements but they are identical to the actual VNAs in

my

possession. I have posted an actual picture of my units as well so you

can

see the images used for identification are identical.

The data I have published shows no significant difference between the

two

clones.

So let's review:

1) No one, including you, have published any data or test results
demonstrating a significant performance advantage for the "real" unit
versus the clones.

2) No one, including you and me, has been able to publish data showing a
significant performance difference among the clones.

3) I have stated but not published data (I am happy to do so) where I
compared the results of my two clones to a spectrum analyzer/tracking
generator/RF bridge combination and found no significant variance in
results among all three devices.

The qualities of the original versus the clones...... so far..... have
been distinctions without differences. Those differences have been

cosmetic

only and no one has shown a resulting measurement discrepancy.

I challenge you or anyone on this board to publish actual data showing
that a clone performs significantly worse than an "original". I don't

think

that has been done. The thread you cite certainly does not support

measured

differences. If you have data please show it. If not then I think we all
need to stop confusing the readers here. Some people have actually

returned

what are likely perfectly good devices because of cosmetics.

WA8TOD

<image.png>