Re: Hardware deficiencies when measuring high impedance with S21
Firmware clone, especially when it is an open source project
is a meaningless term. Hope that clears things up.
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On Tue, 16 Feb 2021 at 17:44, Klaus W?rner <dl5kv@...> wrote: I'm not sure, but I think there are clones for H4 firmware, too. This ist
only a notice of me. Maybe this problem doesn't exist on the V1. I haven't
updated the firmware on V1 for a long time.
On Mon, Feb 15, 2021 at 03:27 PM, Dragan Milivojevic wrote:
This is on H4 not SAA.
There is no such thing as "cloned firmware" so not sure
what you are refering to
--
Klaus, DL5KV
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Re: Hardware deficiencies when measuring high impedance with S21
On Mon, Feb 15, 2021 at 06:43 PM, Dragan Milivojevic wrote:
Calibrated with "0 length through", test jig connected to port2 directly:
You did not provide any detail in your post about your test setup or how you derived R, X and Z from the S21 measurement. I do not recognize the plot formats that you are using. Also you did not describe what component you are measuring. For those that are not familiar with the S21 series method here is an introductory paper. Keysight gives a derivation of the conversion formula. (note S21 is a complex number) If we are to have a discussion on this topic please let the group know a bit about what you are doing... - What VNA is being used - A description of the test jig - What software program or method you are using to convert S21 to complex impedance (R,X) - What component you are measuring. I suggest a 1K SMD resistor of around 1000 ohms because it is easy to see measurement errors and compare results. Another is a 10 pF SMD capacitor or very short lead ceramic type. - When I measure (with a NanoVNA-H4) a 1K resistor on a microstrip with 50 ohm impedance my S21 phase starts at 0 but goes to 17 degrees by 100 MHz. . It should stay close to 0 degrees for a component that has minimal inductance. Roger
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Re: Hardware deficiencies when measuring high impedance with S21
It's a cool firmware. But I think we have to discuss this in an other group. It's not for V1.
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On Mon, Feb 15, 2021 at 11:12 AM, <reuterr@...> wrote:
Hello Klaus,
how about the ojisan firmware.
I have added a patch (2.8 inch LCD only) to make a screenshot with a Python
program,
see:
--
Klaus, DL5KV
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Re: Hardware deficiencies when measuring high impedance with S21
I'm not sure, but I think there are clones for H4 firmware, too. This ist only a notice of me. Maybe this problem doesn't exist on the V1. I haven't updated the firmware on V1 for a long time.
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On Mon, Feb 15, 2021 at 03:27 PM, Dragan Milivojevic wrote:
This is on H4 not SAA.
There is no such thing as "cloned firmware" so not sure
what you are refering to
--
Klaus, DL5KV
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On Tuesday, February 16, 2021, 10:52:15 a.m. EST, barnc4br@... <barnc4br@...> wrote:
a number of thread of similar problems on different units. So I don't think a dif mfg is going to solve the problem. One solution in a thread was to add ESD diodes which may be the best solution. Not sure what the best type are, but the ones specified were listed as "not for new design" and there were a couple opinions as to operating and clamping voltage. So if anyone has a good suggestion RE ESD diodes???
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a number of thread of similar problems on different units. So I don't think a dif mfg is going to solve the problem. One solution in a thread was to add ESD diodes which may be the best solution. Not sure what the best type are, but the ones specified were listed as "not for new design" and there were a couple opinions as to operating and clamping voltage. So if anyone has a good suggestion RE ESD diodes???
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Re: Measuring crystals with NanoVNA. Do the math with my FaseShift Crystal calculator
Wow! Your calculator is great Lex.
Thank you for making it available to the rest of us.
John
AA7US
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TU sir. Yes tried cal right at the terminal no cables. Checked the short and it is. The load is 50 ohms
I am too unsure of loading firmware but a Buddy ham offered Thought might hv been a static discharge as I was measuring the character of an antenna. So who knows. Perhaps he can un mess it up Hihi
Good excuse to buy the H4 from another Chinese company.
73 my friends
Paulk
Paul Kobetz
SKCC 19615C
CWOPS 2589
Rubicon Observatory
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On Feb 15, 2021, at 5:06 PM, Roger Need via groups.io <sailtamarack@...> wrote:
?Paul,
Don't throw in the towel yet.
Did you have the NanoVNA anywhere near a transmitter? I wouldn't put more than about 20 dBm into CH0 or CH1 or you can blow out the front end.
Have you tried connecting it to a PC program like NanoVNA Sharp to see if that works?
There have been problems like this reported before and sometimes it was faulty cal loads or a faulty cable. I know you tested the 50 ohm load but what about the short load? Do the cal right on the SMA connectors without a cable attached to eliminate one source of error. Try setting the frequency range to something low like 30 MHz. and see if that works.
Sometimes users forget to press Reset before doing a cal and Done when finished. I always hit Reset twice to make sure and then check the left of the screen to see that it is cleared.
As a last resort you could try reloading your firmware but only after all other avenues have been exhausted.
Hope you get it working again.
Roger
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Re: measuring Capacitance or Inductance
Instead of taking it personally and flying off the handle how about you offer an explanation as to why the Drake engineers put an electrolytic in this spot in the circuit? I posed this to Garey K4OAH (SK) who had as along and storied a career as you. He called it a "buzz kill" without further explanation I left it at that. 73 -Jim NU0C On Mon, 15 Feb 2021 18:24:37 +0000 "David Eckhardt" <davearea51a@...> wrote: On second thought, forget it. Those of us who have been there, done that
know better. I have a well outfitted RF lab covering to 21 GHz and know
how to use the equipment. I'm through replying to your posts. Go find
someone else to flame......
Reapectfully submetted:
Dave - W?LEV
On Mon, Feb 15, 2021 at 6:17 PM David Eckhardt <davearea51a@...>
wrote:
OK. I'm stupid and really don't know what I'm talking about. I spread
snake oil, saucery, witchcraft, and magic as applied to RF. Smith charts
are just disguised wiggie boards. And, of course, the earth is flat and
all celestial movements are determined by epicycles and epispheres. I
spent 10 years in RF design and the last 30 in EMC/RFI. Color me stupid,
dumb, incapable of handling DC Ohm's Law and don't know which end of the
soldering pen to grab.
I do not appreciate being attacked for my posts. I am working on data and
will post to this group.
Electrolytic, tantalums do NOT make good bypasses for high frequencies. I
proved that to myself decades ago in RF design and following in control of
EMC/RFI. Go build a preamp using only SMD 'electrolytics'. Control RF
emission of a ?P ringing at 3.6 GHz with only SMD 'electrolytics'. I am
taking data on that and will present it to this group. Please hold off on
flaming me further until that work is complete?
Dave - W?LEV
On Mon, Feb 15, 2021 at 2:43 AM Jim Shorney <jshorney@...>
wrote:
Drake TR7/TR4310.
73
-Jim
NU0C
On Mon, 15 Feb 2021 03:31:07 +0100
"Dragan Milivojevic" <d.milivojevic@...> wrote:
Forgot to ask, what's this legendary piece of equipment,
it has transistors so it can't be that good ?
On Mon, 15 Feb 2021 at 03:27, Jim Shorney <jshorney@...> wrote:
Yeah, I remembered that about the one on the left after I sent the
pic.
The one on the right he called a "buzz kill".
73
-Jim
NU0C
On Mon, 15 Feb 2021 02:07:44 +0000 (UTC)
"Bob Albert via groups.io" <bob91343@...> wrote:
The left hand one is bypassed with a .01 so that doesn't count. I
am
puzzled by the other one; what's it supposed to do?
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: Hardware deficiencies when measuring high impedance with S21
Calibrated with "0 length through", test jig connected to port2 directly: X: [image: image.png] R: [image: image.png] Z: [image: image.png] On Tue, 16 Feb 2021 at 01:38, Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Sun, Feb 14, 2021 at 12:55 PM, Dragan Milivojevic wrote:
It has been stated, by multiple members of this group, that due to
hardware
deficiencies (port 2 is not a perfect 50¦¸) and lack of 12 term error
correction,
the "S21 method" can't be used to measure high impedance reliably. Yes this is true. The "S21 series method" is a way of calculating the
complex impedance (R+jX) of a device under test (DUT). Unfortunately it
does not work on a NanoVNA-H or -H4 which are 2 port uni-directional
analyzers for the reasons you outlined in your post.
If you try it you will find that you can calculate the magnitude of a high
impedance |Z| DUT fairly well but the phase angle is not correct except at
very low frequencies. You need the correct phase angle in order to convert
from polar (Z&angle) to polar (R+jX) format.
Users interested in trying this should use a SMD resistor as the DUT which
should have a S21 phase angle very close to zero. You will only get this
at very low frequencies. A small capacitor as the DUT should have a phase
angle near 90 degrees but this will be incorrect as you increase frequency.
I have seen this on several test jigs that I have built.
If users want to try these measurements be very careful with parasitic
capacitance on the test fixture. The capacitance across the terminals
where you connect the DUT has to be well under a pF or the S21 loss in dB
will be incorrect.
Roger
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Re: measuring Capacitance or Inductance
Hi Roger
Man, it sure did go off topic. (Bypass caps; where did that come from? Should be a whole thread on its own.) All I wanted was for someone to tell me how to use nano to measure caps and inds. Well, it forced me to do it right; get some data. I now understand more about component values and frequencies. And as long as I measure parts at very low frequencies, it appears that I get good data. And on three different machines. Now I'm gong to build some test fixtures for real world components and see what happens.
But... I now have all kinds of questions about why those components seem to retain their marked values at high frequencies (if they didn't, you couldn't calculate resonant frequencies), but that's another topic.
BTW: part of the weirdness in the inductor plots (sudden knee in curves) is due t coarseness in frequency steps. But finer steps wouldn't change the general trends. It's a mystery to me.
--
Ed K9EK
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Paul,
Don't throw in the towel yet.
Did you have the NanoVNA anywhere near a transmitter? I wouldn't put more than about 20 dBm into CH0 or CH1 or you can blow out the front end.
Have you tried connecting it to a PC program like NanoVNA Sharp to see if that works?
There have been problems like this reported before and sometimes it was faulty cal loads or a faulty cable. I know you tested the 50 ohm load but what about the short load? Do the cal right on the SMA connectors without a cable attached to eliminate one source of error. Try setting the frequency range to something low like 30 MHz. and see if that works.
Sometimes users forget to press Reset before doing a cal and Done when finished. I always hit Reset twice to make sure and then check the left of the screen to see that it is cleared.
As a last resort you could try reloading your firmware but only after all other avenues have been exhausted.
Hope you get it working again.
Roger
|
Re: measuring Capacitance or Inductance
On Sun, Feb 14, 2021 at 05:03 PM, Ed Krome wrote:
NWDZ board, like it says in the graphs. All calibrated on the same board with
a single cable, as stated. And results were repeatable; I ran it several
times. Are the board standards 100% accurate? Who knows? But the results were
remarkably consistent over specific ranges.
Ed, Sorry that this discussion went so far off topic. It would be really interesting to get an answer to your initial question. From reading your posts and looking at your data I think it might be one of the following. 1. You can see in the photos of your board and the other board there is quite a difference in the layout of the cal loads. You want the reference plane to be right where the device under test (DUT) is connected. On your board it looks like the open and short are not at the same location as the load. This is fairly critical for accurate measurements. Also the DUT should be in the same position as the load especially for higher frequency measurements. 2. Your cap plot is pretty typical. Inductance will make the "apparent capacitance" rise with frequency. In your plot you went to 300 MHz. and if you tried 600 MHz. you will see the circuit at its self -resonant frequency. After that you effectively have an inductor. The exact frequency can be easily determined by plotting the S11 phase angle - it will abruptly change at resonance. I have attached a plot I did of a 10 pf cap with short and long leads which illustrates this point. 3. It is hard to figure out what is going on with your inductor plot. It should not be abruptly changing at 30 MHz. You do get considerable inductance change with ferrite inductors versus frequency because the complex permeability changes. With powdered iron very little and with air-core types it is self capacitance which has the most effect. It would be interesting to see the S11 phase plot and the resistance plot over this frequency range. Regards - Roger
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Re: Hardware deficiencies when measuring high impedance with S21
On Sun, Feb 14, 2021 at 12:55 PM, Dragan Milivojevic wrote:
It has been stated, by multiple members of this group, that due to hardware
deficiencies (port 2 is not a perfect 50¦¸) and lack of 12 term error
correction,
the "S21 method" can't be used to measure high impedance reliably.
Yes this is true. The "S21 series method" is a way of calculating the complex impedance (R+jX) of a device under test (DUT). Unfortunately it does not work on a NanoVNA-H or -H4 which are 2 port uni-directional analyzers for the reasons you outlined in your post. If you try it you will find that you can calculate the magnitude of a high impedance |Z| DUT fairly well but the phase angle is not correct except at very low frequencies. You need the correct phase angle in order to convert from polar (Z&angle) to polar (R+jX) format. Users interested in trying this should use a SMD resistor as the DUT which should have a S21 phase angle very close to zero. You will only get this at very low frequencies. A small capacitor as the DUT should have a phase angle near 90 degrees but this will be incorrect as you increase frequency. I have seen this on several test jigs that I have built. If users want to try these measurements be very careful with parasitic capacitance on the test fixture. The capacitance across the terminals where you connect the DUT has to be well under a pF or the S21 loss in dB will be incorrect. Roger
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Even a reasonably good 10 dB attenuator makes a good dummy load as the
return loss is 20 dB - two passes through the -10 dB circuit. And 20 dB RT
amounts to an SWR of 1.02 : 1. So, you not only have a good 10 dB
attenuator, but a good dummy load as well.
Dave - W?LEV
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On Mon, Feb 15, 2021 at 6:08 PM Luc ON7DQ <on7dq@...> wrote: If it's of any use to anyone, here I described a simple 40 dB / 20W
attenuator I once built
You can also convert a QRP Labs or QRP Guys dummyload into an attenuator
that way, it may not be the "perfect" 50 Ohm IN/OUT attenuator, but surely
good enough to test a QRP rig. Even with ordinary resistors, it will be
useable in the HF range.
Another option is to build a "power sampler", see a link in the post
mentioned above.
As for that "better" video on Youtube that Evan mentioned.
It shows the problems all right, but it does NOT explain it, the maker of
that video cleary missed some points.
"... it goes up and down ... some weird filter ... " huh ?
The simple explanation is that the NanoVNA is limited to 101 points, so
runs over the spectrum in too coarse steps, missing several signals if they
are not on one of those 101 frequencies. Reducing the sweep range may show
more signals, but still miss some.
And nothing weird about the IF filter, but the IF of the NanoVNA is at 5
kHz, so you will see an image signal at 10 kHz offset.
So the NanoVNA is not a spectrum analyzer, but yes, it can be used as a
very crude signal monitor ... if you know what you're doing, and don't
expect too much.
73,
Luc ON7DQ
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: Measuring crystals with NanoVNA. Do the math with my FaseShift Crystal calculator
thanks
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On Mon, Feb 15, 2021, 12:49 PM Lex PH2LB <lex@...> wrote: My Crystal Measuring Adapter for NanoVNA is almost finished. This will
make it much easier to sort out crystals for building filters.
Will I do the faseshift calculations by hand? I think not. I'm just going
to use my "FaseShift Crystal calculator" at
. Just enter the values
and It does the math for you. Simple as that.
Enjoy.
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Measuring crystals with NanoVNA. Do the math with my FaseShift Crystal calculator
My Crystal Measuring Adapter for NanoVNA is almost finished. This will make it much easier to sort out crystals for building filters.
Will I do the faseshift calculations by hand? I think not. I'm just going to use my "FaseShift Crystal calculator" at
. Just enter the values and It does the math for you. Simple as that.
Enjoy.
|
Re: Hardware deficiencies when measuring high impedance with S21
V2 is open source, the later versions are not.
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On Mon, 15 Feb 2021 at 21:02, Jos Stevens <jrs@...> wrote: Hi DiSlord,
The info about updating a V2.2 to V2plus you were so kind send me
recently shows a hardware change of 3 components only, one resistor and
2 capacitors.
If I do understand well, this update makes it possible to increase the
scan speed in the firmware and does not enhance the measuring results
at all.
If so, this update is of less importance to me.
I also learned that there are more hardware differences between the two
versions, do you know what these are and if it is possible to implement
them in the V2.2 ?
I have been looking around, but sofar did not succeed to find the
schematic of the V2plus.
Thanks for your time and best regards,
Jos
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Re: Hardware deficiencies when measuring high impedance with S21
Hi DiSlord,
The info about updating a V2.2 to V2plus you were so kind send me recently shows a hardware change of 3 components only, one resistor and 2 capacitors.
If I do understand well, this update makes it possible to increase the scan speed? in the firmware and does not enhance the measuring results at all.
If so, this update is of less importance to me.
I also learned that there are more hardware differences between the two versions, do you know what these are and if it is possible to implement them in the V2.2 ?
I have been looking around, but sofar did not succeed to find the schematic of the V2plus.
Thanks for your time and best regards,
Jos
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Re: measuring Capacitance or Inductance
By the way, Ed is very well known in the VHF-UHF community. He has designed
and built some really cool solid-state amps for 144, 222 amd 432 MHz in the
200-300 watt range.
Zack W9SZ
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On Fri, Feb 12, 2021 at 8:33 PM Ed Krome <e.krome@...> wrote: Concerning how to measure capacitance and inductance on the RF Demo board
(or any capacitor or inductor), reference
/g/nanovna-users/wiki/16592. I can get the curves shown
in this demo just fine.. but how to read the actual values off of those
curves eludes me. On the item 8 inductor example, if I vary the frequency,
I can make that component read about any value I want. I must be missing
something. Help, please.
--
Ed K9EK
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Roger Need
AA7US
Jim Shorney
Martin Glazer
Lex PH2LB