Re: NanoVNA Saver software version 0.2.1 TDR operation
Reminds me of the rising edge of a square wave pulse, That's how i measure TDR using fast edge pulse from Schmitt trigger inverter and oscilloscope.
Alan W2AEW has good youtube video on it.
Worth a look, hope this helps.
Ray.
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Re: NanoVNA Saver software version 0.2.1 TDR operation
Clyde,
I had the same question. Maybe the author of the software or someone else will reply.
Roger
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Re: First PCB pictures of the V2
Any chance you can add the option of rotating the display graphics 180 deg?
I can see the cables coming out of the bottom being a nuisance in some instances.
And please get rid of that ridiculous "jog" button, it is the most annoying thing since I don't know when.
--
Terry VK5TM
( )
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Re: Some test results using a NanoVNA
You are correct Alan, I was too hasty in my enthusiasm.? And when the result is pure resistance there is resonance.? At frequencies above self resonance an inductor acts as a capacitor.
Which underscores my comment that this is not only a measuring instrument but also a learning tool.
Watching values change with frequency and termination is fascinating.? Try connecting a coil and capacitor to the nano and observe how frequency changes with capacitance.? Or as you squeeze the coil turns.? See how Q changes.
I used to be intimidated by the Smith chart but now its mysteries have unraveled themselves.? Thanks to Joseph Smith for devising it in the late 1930s.
Perceptive readers may have noted my omission of the S1 port, which can be used to see filter response.? If that never gets used, the remaining functions still offer better bang for the buck than any other piece of gear I have found, short of a freebie.? Did I mention that the nano is also a CW and sweep generator?? Output fixed in the range of -10 dBm, 0.1 mW.? Frequency accuracy rated at 2 ppm or so; mine more accurate than that.
Bob K6DDX
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Show quoted text
On Tuesday, December 17, 2019, 01:58:30 PM PST, alan victor <avictor73@...> wrote: On Tue, Dec 17, 2019 at 11:46 AM, Bob Albert wrote: Very good Bob... in your post above... Measuring the bigger ones gives an inductance reading that is too small, since
the distributed capacitance.....
However, the result of distributive C for an inductor which is one appropriate model, shunt C, leads to an inductor value which INCREASES as we approach SRF. The arithmetic for this is; Xt= jwL/(1-w^2LC) where w is radian frequency and Xt is the total reactance for this case. As w^2? approaches 1/(LC), Xt goes through the roof. A larger apparent L. Alan
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Re: First PCB pictures of the V2
On Tue, 17 Dec 2019 at 20:45, hwalker <herbwalker2476@...> wrote: On Tue, Dec 17, 2019 at 10:40 AM, Dale Parfitt wrote:
Thank you Herb, So much traffic, I missed the specs.
====================================================
Dale,
I'd like to add a correction regarding the display size:
Gabriel indicated in her previous message that a working proto-type is
already available using a 3.2" ILI9341 display. A 4" ST7796S display is
being evaluated as an option by menu-driven switchover. Her team will
make a decision about whether to offer two versions for sale.
I would also like to add my voice to the many that would want to purchase this with a larger screen. How does the larger screen you may or may note use compare with the 4.3" on the NanoVNA-F? The 4.3" of the -F is more attractive than 4" for obvious reasons, but how about pixel count, and other technical features about the screen. I don't know if I'm unusual, but for me, the screen is more important than the pure performance, as great performance is no use if you can't see the blinking thing. Of course, if you are going to use it in a lab, with a PC interface, the screen is pretty irrelevant. But there seem to be enough people wanting a decent screen. The 6.5" on my iPhone XS max would be nice. Ouch, that phone was ?1250, so it's not a fair comparison! But seriously, size matters. ?????
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Re: Some test results using a NanoVNA
On Tue, Dec 17, 2019 at 11:46 AM, Bob Albert wrote: Very good Bob... in your post above... Measuring the bigger ones gives an inductance reading that is too small, since
the distributed capacitance.....
However, the result of distributive C for an inductor which is one appropriate model, shunt C, leads to an inductor value which INCREASES as we approach SRF. The arithmetic for this is; Xt= jwL/(1-w^2LC) where w is radian frequency and Xt is the total reactance for this case. As w^2 approaches 1/(LC), Xt goes through the roof. A larger apparent L. Alan
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Re: Some test results using a NanoVNA
Thanks Bob. I'll give it a go. Martin K0BXB On Tue, Dec 17, 2019, 12:12 PM Bob Albert via Groups.Io <bob91343= [email protected]> wrote: How to measure inductance? Very simple. First, you make up an adapter
so you can connect the unknown to the nano S0.
Calibrate the nano. The next step depends on the inductance. Select a
frequency appropriate to the part, 50 kHz for low frequency parts and up
into the high frequencies for rf chokes and into the VHF and UHF for
straight pieces of wire, etc. Since you can't go below 50 kHz that limits
how large an inductor you can measure.
Select Smith chart for display. Read inductance off the screen. You can
read the resistance and compute the Q. If the inductance is very small,
short the leads and take a reading, which you subtract from the final
reading.
With the leads shorted, the Smith chart should have a dot at the left
edge. With the leads open, at the right edge. If the dot is not at the
edge it indicates a low Q.
As a reality check, open up the span to a reasonable frequency range and
move the marker over the range. The inductance should remain relatively
constant. If you open up the frequency range the chart shows a circle. At
some point the circle intersects the horizontal axis at the self resonant
frequency. With high Q you need to keep the span narrow, as the resonanct
frequency can elude measurement since it's very sharp.
The same procedure works for other components. For cables, it will show
electrical length. The way you measure that is to adjust the frequency so
that the Smith circle, for an open end coax, starts at the right and sweeps
down and around up to the left. Where it reaches the center line on the
left is the frequency where the coax is one quarter wave long. The
deviation from the outside circle indicates loss.
Then you put a small pot as a termination for the open coax and adjust it
until the Smith trace shrinks to a dot in the center. At that point,
measure the pot with an Ohmmeter and it will be the characteristic
impedance.
This inexpensive device is not a toy. It's a sophisticated, well designed
piece of first rate test equipment. No ham with tools should be without
one.
Each time I use mine I learn new ways to use it. You can measure diode
capacitance and, with care, can plot a curve of capacitance vs bias to
characterize it as a voltage variable capacitor to use in a PLL or tuning
network. Just don't apply dc to the vna port. Or any voltage. It has its
own generator, very accurate. You can measure transistor and tube
capacitances as well. Or connectors.
If you connect nothing to the nano it will show a residual reading,
sometimes into the femtofarads (one femtofarad is a thousandth of a
picofarad). I never measured a femtofarad before.
I measure crystals this way. This is tricky, as crystals have very high Q
and you need to keep the span very tiny. You need to know the frequency,
which is generally marked on the crystal. Set the nano as that number for
center and a small span, say a few kHz. The crystal frequency will show at
the left edge but not on a circle due to the lack of frequency resolution.
Keep narrowing the span until you can read frequency as close as you like,
although the resolution isn't all that small.
When measuring capacitors the ESR is indicated on the screen. To measure
ESL you measure the self resonant frequency (curve intersecting horizontal
line) and compute it from the classic formula. Or go to a somewhat higher
frequency and read the screen. Remember that the reading is based on a
simulation of the part as a resistance in series with a reactance.
You measure the distributed capacitance and ESL of a resistor the same
way. With care you can get readings that are very accurate. The standard
used for measuring all of this is the 50 Ohm load you use during
calibration so that needs to be very good for precise readings. My
resistor readings are within about 1% of what my GR bridge and HP 3456A
show.
I know the question was how to measure inductance but I got carried away.
Questions?
Bob K6DDX
On Tuesday, December 17, 2019, 04:59:21 AM PST, Oristo <
ormpoa@...> wrote:
> What's needed to connect my NanoVNA- to my Android phone to use the
NanoVNA- Webb app? Just a usbc to usbc cable? /g/nanovna-users/message/4970
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Re: First PCB pictures of the V2
On Tue, Dec 17, 2019 at 10:40 AM, Dale Parfitt wrote:
Thank you Herb, So much traffic, I missed the specs.
====================================================
Dale,
I'd like to add a correction regarding the display size:
Gabriel indicated in her previous message that a working proto-type is already available using a 3.2" ILI9341 display. A 4" ST7796S display is being evaluated as an option by menu-driven switchover. Her team will make a decision about whether to offer two versions for sale.
- Herb
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Roger, it's really very easy to make your own cables.
There are SMA connectors that use the 'solder the center' and 'crimp the shield' type of construction. I use this method on all my connectors, SMA,BNC,PL-259 and N.
These ensure the center pin is EXACTLY correct. I use the following cable: You will need a crimp tool for the correct size sleeve.
RG-316
RG-316DS (double shield
RG-174DS " (Belden)
My favorite is the RG-316DS,
ron
N4UE
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Re: Some test results using a NanoVNA
One addendum regarding inductance.? I did mention that 50 kHz as a low limit prevents measurement of large inductances.
I just measured a few and got good results up to around 50 mH.? My inductance stock doesn't have specially made parts so the higher inductances have very low self resonat frequencies.? Measuring the bigger ones gives an inductance reading that is too small, since the distributed capacitance begins to shunt the inductance.
So for L up to a few dozen millihenries it's usable but not terribly accurate.? Down to the microhenries and below it's good.? Inductance of a straight wire is easily measured if the test fixture can accommodate it.? Shorting the leads gives a residual reading you can subtract but it's not that simple, as we are dealing with magnetic fields and any change in position messes it up.
The same is true for capacitances below several dozen picofarads.
Bob
toggle quoted message
Show quoted text
On Tuesday, December 17, 2019, 10:12:15 AM PST, Bob Albert via Groups.Io <bob91343@...> wrote: How to measure inductance?? Very simple.? First, you make up an adapter so you can connect the unknown to the nano S0. Calibrate the nano.? The next step depends on the inductance.? Select a frequency appropriate to the part, 50 kHz for low frequency parts and up into the high frequencies for rf chokes and into the VHF and UHF for straight pieces of wire, etc.? Since you can't go below 50 kHz that limits how large an inductor you can measure. Select Smith chart for display.? Read inductance off the screen.? You can read the resistance and compute the Q.? If the inductance is very small, short the leads and take a reading, which you subtract from the final reading. With the leads shorted, the Smith chart should have a dot at the left edge.? With the leads open, at the right edge.? If the dot is not at the edge it indicates a low Q. As a reality check, open up the span to a reasonable frequency range and move the marker over the range.? The inductance should remain relatively constant.? If you open up the frequency range the chart shows a circle.? At some point the circle intersects the horizontal axis at the self resonant frequency.? With high Q you need to keep the span narrow, as the resonanct frequency can elude measurement since it's very sharp. The same procedure works for other components.? For cables, it will show electrical length.? The way you measure that is to adjust the frequency so that the Smith circle, for an open end coax, starts at the right and sweeps down and around up to the left.? Where it reaches the center line on the left is the frequency where the coax is one quarter wave long.? The deviation from the outside circle indicates loss. Then you put a small pot as a termination for the open coax and adjust it until the Smith trace shrinks to a dot in the center.? At that point, measure the pot with an Ohmmeter and it will be the characteristic impedance. This inexpensive device is not a toy.? It's a sophisticated, well designed piece of first rate test equipment.? No ham with tools should be without one. Each time I use mine I learn new ways to use it.? You can measure diode capacitance and, with care, can plot a curve of capacitance vs bias to characterize it as a voltage variable capacitor to use in a PLL or tuning network.? Just don't apply dc to the vna port.? Or any voltage.? It has its own generator, very accurate.? You can measure transistor and tube capacitances as well.? Or connectors. If you connect nothing to the nano it will show a residual reading, sometimes into the femtofarads (one femtofarad is a thousandth of a picofarad).? I never measured a femtofarad before. I measure crystals this way.? This is tricky, as crystals have very high Q and you need to keep the span very tiny.? You need to know the frequency, which is generally marked on the crystal.? Set the nano as that number for center and a small span, say a few kHz.? The crystal frequency will show at the left edge but not on a circle due to the lack of frequency resolution.? Keep narrowing the span until you can read frequency as close as you like, although the resolution isn't all that small. When measuring capacitors the ESR is indicated on the screen.? To measure ESL you measure the self resonant frequency (curve intersecting horizontal line) and compute it from the classic formula.? Or go to a somewhat higher frequency and read the screen.? Remember that the reading is based on a simulation of the part as a resistance in series with a reactance. You measure the distributed capacitance and ESL of a resistor the same way.? With care you can get readings that are very accurate.? The standard used for measuring all of this is the 50 Ohm load you use during calibration so that needs to be very good for precise readings.? My resistor readings are within about 1% of what my GR bridge and HP 3456A show. I know the question was how to measure inductance but I got carried away. Questions? Bob K6DDX ? ? On Tuesday, December 17, 2019, 04:59:21 AM PST, Oristo <ormpoa@...> wrote: > What's needed to connect my NanoVNA- to my Android phone to use the NanoVNA- Webb app? Just a usbc to usbc cable? /g/nanovna-users/message/4970
|
I have read numerous comments that state that the quality of the cables supplied with the NanoVNA is poor. However Hugen has supplied good calibration terminators in his NanoVNA-H in the gift box package. Has anyone tested the cables in the NanoVNA-H gift box to determine their quality and impedance?
Any recommended cables from suppliers in North America?
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Re: errors of "error" models
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Re: First PCB pictures of the V2
Great stuff. Sorry if this has been answered elsewhere but are there plans for Bluetooth?
Thanks,
Brian WB8AM
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Re: First PCB pictures of the V2
Thank you Herb,
So much traffic, I missed the specs.
Dale W4OP
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Show quoted text
-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of hwalker Sent: Tuesday, December 17, 2019 1:29 PM To: [email protected]Subject: Re: [nanovna-users] First PCB pictures of the V2 On Tue, Dec 17, 2019 at 10:10 AM, Dale Parfitt wrote: How does this differ from the 4.3" NanoVNA-F already available? ==================================================================== Recapping from information info previously provided in this thread and elsewhere: 1. Frequency range expected to be 50kHz to 3GHz. 2. Typical S11 floor is -50dB up to 2GHz and -40dB up to 3GHz 3. -70dB S21 floor below 2GHz and -60dB floor up to 3GHz 4. 4 inch display currently being prototyped - Herb
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Re: First PCB pictures of the V2
On Tue, Dec 17, 2019 at 10:10 AM, Dale Parfitt wrote:
How does this differ from the 4.3" NanoVNA-F already available?
====================================================================
Recapping from information info previously provided in this thread and elsewhere:
1. Frequency range expected to be 50kHz to 3GHz.
2. Typical S11 floor is -50dB up to 2GHz and -40dB up to 3GHz
3. -70dB S21 floor below 2GHz and -60dB floor up to 3GHz
4. 4 inch display currently being prototyped
- Herb
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Re: Are any of the NanoVNA sold on Amazon any better or worse than any others? Is there a better U.S. site to order from?
On Tue, Dec 17, 2019 at 05:20 AM, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
With a well written specification, following closely the format of a major VNA manufacturer like Keysight, some users would be in a position to determine if the specifications are poorer. Then poor sellers would soon get a bad reputation.
===============================================================================================
In my opinion the vast majority of hobbyists that the NanoVNA-H are targeted to are primarily concerned with frequency range, return loss, and thru loss specifications. Manufacturers of these hobbyist devices have limited resources. Detailed specifications as produced by a major manufacturer such as Keysight are probably best left to the community of open source users who in a lot of cases have better equipment and know-how to produce these specifications.
The NanoVNA-H has a track record of publicly releasing its schematics and frequently releasing firmware updates in response to user feedback. The NanoVNA-F, which has been out for a while now, has chosen not to publicly release its schematics, has not had any significant firmware upgrades since its release, and has only a quick start guide for documentation. Yet the owners of the NanoVNA-F seem willing to overlook these drawbacks because of larger display size and other considerations, such as metal case and easier firmware upgrade. That is a good example of what specifications are really important to the majority of buyers of these low cost VNA's.
- Herb
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Re: Some test results using a NanoVNA
How to measure inductance?? Very simple.? First, you make up an adapter so you can connect the unknown to the nano S0. Calibrate the nano.? The next step depends on the inductance.? Select a frequency appropriate to the part, 50 kHz for low frequency parts and up into the high frequencies for rf chokes and into the VHF and UHF for straight pieces of wire, etc.? Since you can't go below 50 kHz that limits how large an inductor you can measure. Select Smith chart for display.? Read inductance off the screen.? You can read the resistance and compute the Q.? If the inductance is very small, short the leads and take a reading, which you subtract from the final reading. With the leads shorted, the Smith chart should have a dot at the left edge.? With the leads open, at the right edge.? If the dot is not at the edge it indicates a low Q. As a reality check, open up the span to a reasonable frequency range and move the marker over the range.? The inductance should remain relatively constant.? If you open up the frequency range the chart shows a circle.? At some point the circle intersects the horizontal axis at the self resonant frequency.? With high Q you need to keep the span narrow, as the resonanct frequency can elude measurement since it's very sharp. The same procedure works for other components.? For cables, it will show electrical length.? The way you measure that is to adjust the frequency so that the Smith circle, for an open end coax, starts at the right and sweeps down and around up to the left.? Where it reaches the center line on the left is the frequency where the coax is one quarter wave long.? The deviation from the outside circle indicates loss. Then you put a small pot as a termination for the open coax and adjust it until the Smith trace shrinks to a dot in the center.? At that point, measure the pot with an Ohmmeter and it will be the characteristic impedance. This inexpensive device is not a toy.? It's a sophisticated, well designed piece of first rate test equipment.? No ham with tools should be without one. Each time I use mine I learn new ways to use it.? You can measure diode capacitance and, with care, can plot a curve of capacitance vs bias to characterize it as a voltage variable capacitor to use in a PLL or tuning network.? Just don't apply dc to the vna port.? Or any voltage.? It has its own generator, very accurate.? You can measure transistor and tube capacitances as well.? Or connectors. If you connect nothing to the nano it will show a residual reading, sometimes into the femtofarads (one femtofarad is a thousandth of a picofarad).? I never measured a femtofarad before. I measure crystals this way.? This is tricky, as crystals have very high Q and you need to keep the span very tiny.? You need to know the frequency, which is generally marked on the crystal.? Set the nano as that number for center and a small span, say a few kHz.? The crystal frequency will show at the left edge but not on a circle due to the lack of frequency resolution.? Keep narrowing the span until you can read frequency as close as you like, although the resolution isn't all that small. When measuring capacitors the ESR is indicated on the screen.? To measure ESL you measure the self resonant frequency (curve intersecting horizontal line) and compute it from the classic formula.? Or go to a somewhat higher frequency and read the screen.? Remember that the reading is based on a simulation of the part as a resistance in series with a reactance. You measure the distributed capacitance and ESL of a resistor the same way.? With care you can get readings that are very accurate.? The standard used for measuring all of this is the 50 Ohm load you use during calibration so that needs to be very good for precise readings.? My resistor readings are within about 1% of what my GR bridge and HP 3456A show. I know the question was how to measure inductance but I got carried away. Questions? Bob K6DDX On Tuesday, December 17, 2019, 04:59:21 AM PST, Oristo <ormpoa@...> wrote: > What's needed to connect my NanoVNA- to my Android phone to use the NanoVNA- Webb app? Just a usbc to usbc cable? /g/nanovna-users/message/4970
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Re: First PCB pictures of the V2
How does this differ from the 4.3" NanoVNA-F already available?
Tnx,
Dale W4OP
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of John Ackermann N8UR Sent: Tuesday, December 17, 2019 1:05 PM To: [email protected]Subject: Re: [nanovna-users] First PCB pictures of the V2 Just another voice asking for a large screen version -- I would really like that! Thanks for all you're doing! John ---- On 12/17/19 11:44 AM, Gabriel Tenma White wrote: shields: I'll be characterizing the sensitivity to external interference before making a final decision on which shields to include.
jog switch: in our tests the switch's position didn't affect usability with cables connected. The switch is less likely to be damaged because it does not protrude as much as it does on the original Nano, and in this position the RF connectors actually protect it from being jammed.
firmware upgrade: the F303 used in the V2 does not have a built in bootloader, so we will look into choices of bootloaders. Most likely the upgrade process will be similar to the -F, but I can't make any promises yet.
display: The ST7796S is command-compatible with the ILI9341 so menu-driven switchover may be doable. I can see an image when I swap a ST7796S display in without any code changes, just in a corner of the screen and flipped. The team will make a decision about whether to offer two versions for sale.
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Re: First PCB pictures of the V2
Just another voice asking for a large screen version -- I would really
like that!
Thanks for all you're doing!
John
----
toggle quoted message
Show quoted text
On 12/17/19 11:44 AM, Gabriel Tenma White wrote: shields: I'll be characterizing the sensitivity to external interference before making a final decision on which shields to include.
jog switch: in our tests the switch's position didn't affect usability with cables connected. The switch is less likely to be damaged because it does not protrude as much as it does on the original Nano, and in this position the RF connectors actually protect it from being jammed.
firmware upgrade: the F303 used in the V2 does not have a built in bootloader, so we will look into choices of bootloaders. Most likely the upgrade process will be similar to the -F, but I can't make any promises yet.
display: The ST7796S is command-compatible with the ILI9341 so menu-driven switchover may be doable. I can see an image when I swap a ST7796S display in without any code changes, just in a corner of the screen and flipped. The team will make a decision about whether to offer two versions for sale.
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Re: First PCB pictures of the V2
Good job, perhaps offer the option to rotate display 180 degrees so connectors and jog switch point away from user.
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Roger Need
Dr. David Kirkby, Kirkby Microwave Ltd
gin&pez@arg
Brian Garber