开云体育

YouTube has become less and less useful with every passing year -- not an
insignificant amount of the "how to" and "learning" videos there on almost
any subject are of dubious quality and a waste of time. Here, let's
translate:

"Your Widget Made Easy" (Translation: I'm going to bore you to death by
showing you what everyone else has already shown you.)
"The Amazing Widget" (Translation: I'm going to spend ten minutes showing
you what's in the box because I just got it today.)
"Polarized Vectorization and Geophysics Speed Measurements using your
Widget" (Translation: I'm going to bamboozle you with nonsense you don't
care about and make myself look smart.)

Sorry if I sound grumpy, but I'm pretty much fed up with trying to learn
via YouTube. I'd rather read groups like this and absorb information. The
NanoVNA is a complex tool with a lot of capability -- it takes time to
understand the features.

73 - Steve, KW4H

?On 8/20/21, 10:31 AM, "[email protected] on behalf of Philip
Stevens" <[email protected] on behalf of philg3ses@...> wrote:

I agree with Dave Kirkby about the poor quality of many YouTube videos.

A special Thanks to everyone here!

I got it to work!

Now a general question about inductance.

I know diameter, wire gauge, spacing of turns, number of turns all determine the amount of inductance a coil has.

Now am I seeing something odd? Or need a different test jig? Or does also number of turns effect how much each turn equals in value of inductance.

Measuring the amount of "L" in the output of a SB-220 amp coil system.

From one end to erach tap is coming in right where it should be.

But just for curiosity sake I measured each coil separately.

OK got those numbers, Then is where I am somewhat a Huh?

OK three coils exact the same in every way except for number of turns.

so I took Inductance value, divided by number of turns, to say get a rough estimate what amount of "L" is from each turn.

Thing is tho, The amount of "L" in each turn is very different in each coil. It seems that, as you get more turns, each turn is making more "L" also.

Is this "Normal"?

Joe WB9SBD

On 8/20/2021 12:22 PM, Victor Reijs wrote:

If you want to measure inductance, it is normally starting with low
frequencies. On my example I gave a range from 10KHz to 1MHz (see the
screengrab).
You can include higher frequencies and then you can see perhaps when the
capacitance of the inductance starts to resonance (Phase=0).

All the best,

Victor


Op vr 20 aug. 2021 om 17:52 schreef Roger Need via groups.io <sailtamarack=
[email protected]>:

On Fri, Aug 20, 2021 at 08:17 AM, Steven Reed wrote:

Following this with great interest. The DUT under test here is an IF

can and

I'm so far getting nothing on the screen.

If you are using an IF can (transformer)? they are usually a tuned circuit
consisting of an inductor in parallel with a capacitor.? So you would be
looking for a resonance point near the rated frequency.? Note that this
occurs at a specified input/output impedance.? Most of the time you test IF
transformers with an S21 measurement by connecting them between CH0 (Port1)
and CH1 (Port2) using an appropriate impedance matching network.

I do not understand what you mean by "getting nothing on the screen".
Post a screenshot.? NanoVNA Saver has a screenshot capture feature or use
your cellphone

???? You say,

???? Step by step,

???? 1. Set the frequency range with the Stimulus menu.

???? What freq range should I put in there?

You put in the frequency range of interest to you.? It has to be done
knowing the limitations of the NanoVNA and the characteristics of the
device under test (DUT)

The NanoVNA will only go down to 10 kHz.? However measurements this low
will have a high degree of uncertainty because the resistance and reactance
are very low which results in a reflection coefficient that is nearly 1.? I
posted a plot showing this in an earlier post.

If you set the upper limit too high the results will be inaccurate due to
stray inductance and capacitance of your test jig.? Even with an excellent
test jig the DUT resistance and reactance will be so high that the
reflection coefficient will be nearly 1 so the results will be very
inaccurate.

Also as you increase frequency the self capacitance of the inductor will
have a bigger effect on measured reactance and at one point you will reach
the self-resonant frequency.? After that the inductor will act like a
capacitor.?? An example of this is shown below for a 330 uH inductor from
my junk box..

Roger

A special Thanks to everyone here!

I got it to work!

Now a general question about inductance.

I know diameter, wire gauge, spacing of turns, number of turns all
determine the amount of inductance a coil has.

Now am I seeing something odd? Or need a different test jig? Or does
also number of turns effect how much each turn equals in value of
inductance.

Measuring the amount of "L" in the output of a SB-220 amp coil system.

From one end to erach tap is coming in right where it should be.

But just for curiosity sake I measured each coil separately.

OK got those numbers, Then is where I am somewhat a Huh?

OK three coils exact the same in every way except for number of turns.

so I took Inductance value, divided by number of turns, to say get a
rough estimate what amount of "L" is from each turn.

Thing is tho, The amount of "L" in each turn is very different in each
coil. It seems that, as you get more turns, each turn is making more "L"
also.

Is this "Normal"?

Joe WB9SBD

On 8/20/2021 12:22 PM, Victor Reijs wrote:

If you want to measure inductance, it is normally starting with low
frequencies. On my example I gave a range from 10KHz to 1MHz (see the
screengrab).
You can include higher frequencies and then you can see perhaps when the
capacitance of the inductance starts to resonance (Phase=0).

All the best,

Victor


Op vr 20 aug. 2021 om 17:52 schreef Roger Need via groups.io

<sailtamarack=

[email protected]>:

On Fri, Aug 20, 2021 at 08:17 AM, Steven Reed wrote:

Following this with great interest. The DUT under test here is an IF

can and

I'm so far getting nothing on the screen.

If you are using an IF can (transformer) they are usually a tuned

circuit

consisting of an inductor in parallel with a capacitor. So you would be
looking for a resonance point near the rated frequency. Note that this
occurs at a specified input/output impedance. Most of the time you

test IF

transformers with an S21 measurement by connecting them between CH0

(Port1)

and CH1 (Port2) using an appropriate impedance matching network.

I do not understand what you mean by "getting nothing on the screen".
Post a screenshot. NanoVNA Saver has a screenshot capture feature or

use

your cellphone

You say,

Step by step,

1. Set the frequency range with the Stimulus menu.

What freq range should I put in there?

You put in the frequency range of interest to you. It has to be done
knowing the limitations of the NanoVNA and the characteristics of the
device under test (DUT)

The NanoVNA will only go down to 10 kHz. However measurements this low
will have a high degree of uncertainty because the resistance and

reactance

are very low which results in a reflection coefficient that is nearly

1. I

posted a plot showing this in an earlier post.

If you set the upper limit too high the results will be inaccurate due

to

stray inductance and capacitance of your test jig. Even with an

excellent

test jig the DUT resistance and reactance will be so high that the
reflection coefficient will be nearly 1 so the results will be very
inaccurate.

Also as you increase frequency the self capacitance of the inductor will
have a bigger effect on measured reactance and at one point you will

reach

the self-resonant frequency. After that the inductor will act like a
capacitor. An example of this is shown below for a 330 uH inductor

from

my junk box..

Roger

On 8/20/21 11:36 AM, Joe WB9SBD wrote:

A special Thanks to everyone here!

I got it to work!

Now a general question about inductance.

I know diameter, wire gauge, spacing of turns, number of turns all determine the amount of inductance a coil has.

Now am I seeing something odd? Or need a different test jig? Or does also number of turns effect how much each turn equals in value of inductance.

Measuring the amount of "L" in the output of a SB-220 amp coil system.

From one end to erach tap is coming in right where it should be.

But just for curiosity sake I measured each coil separately.

OK got those numbers, Then is where I am somewhat a Huh?

OK three coils exact the same in every way except for number of turns.

so I took Inductance value, divided by number of turns, to say get a rough estimate what amount of "L" is from each turn.

Thing is tho, The amount of "L" in each turn is very different in each coil. It seems that, as you get more turns, each turn is making more "L" also.

Is this "Normal"?

Joe WB9SBD

Inductance is proportional to the number of turns *squared*. It's actually a bit less, because the turn on one end of a long skinny air core coil isn't as tightly coupled to the turn on the other end, as it is to it's neighbor.


Simple example - assume you've got a 3 turn coil.

Inductance is the voltage you see for a particular varying current.

Looking at turn 1.

It sees a voltage from its self inductance. But it also sees a voltage from the field from the current through turn 2 and the field from turn 3 as well.

Turn 2 sees a voltage from itself, and a voltage from the field from turn 1 and from turn 3.

And so on.

If the turns are *tightly coupled* (i.e. they're on a magnetic core), then it's easy..

If the voltage from a 1 turn coil, by itself, is 1 Volt, with a fixed current.

Then the first turn has 3 volts, the second turn has 3 volts, and the third turn has 3 volts. They're all in series, so the total voltage is 9 (=3^2).

--

If the turns aren't as tightly coupled (say, 90% for adjacent, and 80% for 2 turns away, just to make the numbers easier) the voltages work out like this:

Turn 1: 1 + 0.9 (from turn 2) + 0.8 (from turn 3)

Turn 2: 0.9 (from turn 1) + 1 + 0.9 (from turn 3)

Turn 3: 0.8 (from turn 1) + 0.9 (from turn 2) + 1

Or, 2.7+2.8+2.7, or 8.2 (not quite N^2)

If you want to measure inductance, it is normally starting with low
frequencies. On my example I gave a range from 10KHz to 1MHz (see the
screengrab).
You can include higher frequencies and then you can see perhaps when the
capacitance of the inductance starts to resonance (Phase=0).

All the best,

Victor


Op vr 20 aug. 2021 om 17:52 schreef Roger Need via groups.io <sailtamarack=
[email protected]>:

On Fri, Aug 20, 2021 at 08:17 AM, Steven Reed wrote:

Following this with great interest. The DUT under test here is an IF

can and

I'm so far getting nothing on the screen.

If you are using an IF can (transformer) they are usually a tuned circuit
consisting of an inductor in parallel with a capacitor. So you would be
looking for a resonance point near the rated frequency. Note that this
occurs at a specified input/output impedance. Most of the time you test IF
transformers with an S21 measurement by connecting them between CH0 (Port1)
and CH1 (Port2) using an appropriate impedance matching network.

I do not understand what you mean by "getting nothing on the screen".
Post a screenshot. NanoVNA Saver has a screenshot capture feature or use
your cellphone

You say,

Step by step,

1. Set the frequency range with the Stimulus menu.

What freq range should I put in there?

You put in the frequency range of interest to you. It has to be done
knowing the limitations of the NanoVNA and the characteristics of the
device under test (DUT)

The NanoVNA will only go down to 10 kHz. However measurements this low
will have a high degree of uncertainty because the resistance and reactance
are very low which results in a reflection coefficient that is nearly 1. I
posted a plot showing this in an earlier post.

If you set the upper limit too high the results will be inaccurate due to
stray inductance and capacitance of your test jig. Even with an excellent
test jig the DUT resistance and reactance will be so high that the
reflection coefficient will be nearly 1 so the results will be very
inaccurate.

Also as you increase frequency the self capacitance of the inductor will
have a bigger effect on measured reactance and at one point you will reach
the self-resonant frequency. After that the inductor will act like a
capacitor. An example of this is shown below for a 330 uH inductor from
my junk box..

Roger

Ken,

Unless you're going to add a 50R resistor somewhere, L and C won't give you
50R in any combination - well, unless there's a lot of loss somewhere.

Series LC gives you a short-circuit at resonance, although the inductor's
finite Q will mean it's a small resistance instead (Rs = X/Q).
Parallel LC gives you an open circuit at resonance, but finite inductor Q
means you'll get finite parallel resistance (Rp = Q*X). Actually, maximum Z
doesn't occur quite at resonance in a parallel resonator, but that's too
complicated to explain in a few words.

You could add a known component to find either of these two conditions. The
series resonance will be more accurate. In that case, you find the
frequency which passes closest to a short on the Smith chart. Then work out
the unknown component from L = 1/((2*pi*f)^2*C). Notice that you are close
to one of the conditions the VNA was calibrated to.

However, you need to be sure you're well away from the inductor's
self-resonant frequency (SRF). If you measure the inductor on its own,
that's where the Smith chart locus first passes close to the open circuit
condition. So you want to select a known component that gets you resonance
well below the SRF. Although you might want to know the inductance at the
frequency you're actually intending to use it at.

73 Andy, G4KNO.


On Fri, Aug 20, 2021 at 4:30 PM Kenneth Hendrickson via groups.io
<dsp_stap=
[email protected]> wrote:

--- On Friday, August 20, 2021, 09:58:05 AM EDT, Dr. David Kirkby,

Kirkby

Microwave Ltd <drkirkby@...> wrote:

There's a lot of people commenting on this thread that don't seem to
appreciate that the uncertainty in VNA measurements increases

significantly

at high reflection coefficients.

So here is my proposed method for measuring inductors and capacitors:

1) Use a test jig to minimize stray inductance and capacitance.
2) Have a set of known capacitors for measuring unknown inductors.
3) Have a set of known inductors for measuring unknown capacitors.
4) When measuring an unknown X>0, use a known capacitor.
4a) Use the known capacitor to move the impedance as close to 50 Ohms as
possible.
4b) Back out the unknown inductor value from the known capacitor value

and

the measured Z.
5) When measuring an unknown X<0, use a known inductor.
5a) Use the known inductor to move the impedance as close to 50 Ohms as
possible.
5b) Back out the unknown capacitor value from the known inductor value

and

the measured Z.

That is the most accurate method I can think of.

73,
Ken N8KH

PS Of course, use a low enough frequency.

On Fri, Aug 20, 2021 at 08:17 AM, Steven Reed wrote:

Following this with great interest. The DUT under test here is an IF

can and

I'm so far getting nothing on the screen.

If you are using an IF can (transformer) they are usually a tuned circuit
consisting of an inductor in parallel with a capacitor. So you would be
looking for a resonance point near the rated frequency. Note that this
occurs at a specified input/output impedance. Most of the time you test IF
transformers with an S21 measurement by connecting them between CH0 (Port1)
and CH1 (Port2) using an appropriate impedance matching network.

I do not understand what you mean by "getting nothing on the screen".
Post a screenshot. NanoVNA Saver has a screenshot capture feature or use
your cellphone

You say,

Step by step,

1. Set the frequency range with the Stimulus menu.

What freq range should I put in there?

You put in the frequency range of interest to you. It has to be done
knowing the limitations of the NanoVNA and the characteristics of the
device under test (DUT)

The NanoVNA will only go down to 10 kHz. However measurements this low
will have a high degree of uncertainty because the resistance and reactance
are very low which results in a reflection coefficient that is nearly 1. I
posted a plot showing this in an earlier post.

If you set the upper limit too high the results will be inaccurate due to
stray inductance and capacitance of your test jig. Even with an excellent
test jig the DUT resistance and reactance will be so high that the
reflection coefficient will be nearly 1 so the results will be very
inaccurate.

Also as you increase frequency the self capacitance of the inductor will
have a bigger effect on measured reactance and at one point you will reach
the self-resonant frequency. After that the inductor will act like a
capacitor. An example of this is shown below for a 330 uH inductor from
my junk box..

Roger