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Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club meetings. I've had my Nano VNA for about four months now, and each time I play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE and RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy: GRAMPY pushing GRANDCHILD on a swing.
Even little grandkids know that GRAMPY has to push the swing at just the right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that. If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy at just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were already in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we are really interested in what the readings are at the ANTENNA junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a 1/4 wavelength of RG213 (6 feet) did ROTATE the impedance values on the Smith Chart. I "knew" what was going to happen, but still smiled when I saw it with my own eyes. Yet, adding 6 feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR readings on 10m (28-29 MHz) to the REFLECTION COEFFICIENT, and to the RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a NANO VNA talk (as pdf slides).
If any clubs are looking for a speaker, I am all in. I learn a lot by giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on these PDF slides to others.
de Barry Feierman k3eui
|
Barry, great slide presentation.?
However, you ask questions in a number of the slides and have a few quizzes but don't provide an appendix or any presentation notes with the answers.?
Can you please add either of those to the end of the slides to make them a great standalone educational tool?
Thanks
Larry
On Sat., 30 Jan. 2021 at 10:20 a.m., Barry Feierman<k3euibarry@...> wrote: Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club meetings. I've had my Nano VNA for about four months now, and each time I play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE and RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy:? GRAMPY? pushing GRANDCHILD? on a swing.
Even little grandkids know that GRAMPY has to push the swing at just the right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that.? If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy at just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were already in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we are really interested in what the readings are at the? ANTENNA? junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a? 1/4 wavelength of RG213? (6 feet) did ROTATE the impedance values on the Smith Chart.? I "knew" what was going to happen, but still smiled when I saw it with my own eyes.? Yet, adding 6 feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR readings on 10m? (28-29 MHz) to the REFLECTION COEFFICIENT, and to the RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a? NANO VNA talk (as? pdf slides).
If any clubs are looking for a speaker, I am all in.? I learn a lot by giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on these PDF? slides to others.
de? Barry Feierman? k3eui
|
Very interesting. I was quite shocked that you didn¡¯t use metric units for the calculations though. This would be my suggestion: use metric units.
JD
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Show quoted text
On Jan 30, 2021, at 07:23, Barry Feierman <k3euibarry@...> wrote:
?Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club meetings. I've had my Nano VNA for about four months now, and each time I play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE and RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy: GRAMPY pushing GRANDCHILD on a swing.
Even little grandkids know that GRAMPY has to push the swing at just the right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that. If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy at just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were already in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we are really interested in what the readings are at the ANTENNA junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a 1/4 wavelength of RG213 (6 feet) did ROTATE the impedance values on the Smith Chart. I "knew" what was going to happen, but still smiled when I saw it with my own eyes. Yet, adding 6 feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR readings on 10m (28-29 MHz) to the REFLECTION COEFFICIENT, and to the RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a NANO VNA talk (as pdf slides).
If any clubs are looking for a speaker, I am all in. I learn a lot by giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on these PDF slides to others.
de Barry Feierman k3eui
<Nano VNA Analyzer Jan 28.pdf>
|
Barry,
I thought you might enjoy this description of the resonant swing set by Graham Johnson in his book . - High Speed Signal Propagation - Advanced Black Magic (1993).
Roger
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A minor correction: the authors are Dr. Howard Johnson and Martin Graham.
They authored two books (including the one cited below) and they are both excellent.
DaveD
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Show quoted text
On Jan 30, 2021, at 14:58, Roger Need via groups.io <sailtamarack@...> wrote:
Barry,
I thought you might enjoy this description of the resonant swing set by Graham Johnson in his book . - High Speed Signal Propagation - Advanced Black Magic (1993).
Roger
<Resonance - swing set.PNG>
|
Personally, I'm more at home in metric than our "kings foot" set of units! However, if I had used metric, all the hams over here in the good 'ol USofA would bellyache they couldn't deal with 2.54 cm/inch (conversion is on most calculators) or, heaven forbid, Kelvins instead of degrees F. When presenting, I warn the audience up-front that miles per hour has no place in Fields and Waves in specifying c, only 3E8 m/sec and other metric units shall be used. Dave - W?LEV (Born a Nerd, Always a Nerd........) On Sat, Jan 30, 2021 at 7:24 PM Jean-Denis Muys via groups.io <jdmuys= [email protected]> wrote: Very interesting. I was quite shocked that you didn¡¯t use metric units for
the calculations though. This would be my suggestion: use metric units.
JD
On Jan 30, 2021, at 07:23, Barry Feierman <k3euibarry@...> wrote:
?Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club meetings. I've had my Nano VNA for about four months now, and each time I
play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE and
RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy: GRAMPY pushing GRANDCHILD on a swing.
Even little grandkids know that GRAMPY has to push the swing at just the right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that. If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy at just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were already in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we are really interested in what the readings are at the ANTENNA junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a 1/4 wavelength of RG213 (6 feet) did
ROTATE the impedance values on the Smith Chart. I "knew" what was going to
happen, but still smiled when I saw it with my own eyes. Yet, adding 6
feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR
readings on 10m (28-29 MHz) to the REFLECTION COEFFICIENT, and to the
RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a NANO VNA talk (as pdf slides).
If any clubs are looking for a speaker, I am all in. I learn a lot by giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on these
PDF slides to others.
de Barry Feierman k3eui
<Nano VNA Analyzer Jan 28.pdf>
-- *Dave - W?LEV* *Just Let Darwin Work*
|
Here!! Here!!. We should have been more persistent in the 1960 when the USA tried to move to the metric system. *Clyde K. Spencer* On Sat, Jan 30, 2021 at 5:34 PM David Eckhardt <davearea51a@...> wrote: Personally, I'm more at home in metric than our "kings foot" set of units!
However, if I had used metric, all the hams over here in the good 'ol USofA
would bellyache they couldn't deal with 2.54 cm/inch (conversion is on most
calculators) or, heaven forbid, Kelvins instead of degrees F. When
presenting, I warn the audience up-front that miles per hour has no place
in Fields and Waves in specifying c, only 3E8 m/sec and other metric units
shall be used.
Dave - W?LEV
(Born a Nerd, Always a Nerd........)
On Sat, Jan 30, 2021 at 7:24 PM Jean-Denis Muys via groups.io <jdmuys=
[email protected]> wrote:
Very interesting. I was quite shocked that you didn¡¯t use metric units for
the calculations though. This would be my suggestion: use metric units.
JD
On Jan 30, 2021, at 07:23, Barry Feierman <k3euibarry@...> wrote:
?Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club
meetings. I've had my Nano VNA for about four months now, and each time I
play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE and
RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy: GRAMPY pushing GRANDCHILD on a swing.
Even little grandkids know that GRAMPY has to push the swing at just
the
right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that. If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy at just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were already in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push
those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we are really interested in what the readings are at the ANTENNA junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a 1/4 wavelength of RG213 (6 feet) did
ROTATE the impedance values on the Smith Chart. I "knew" what was going to
happen, but still smiled when I saw it with my own eyes. Yet, adding 6
feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR
readings on 10m (28-29 MHz) to the REFLECTION COEFFICIENT, and to the
RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a NANO VNA talk (as pdf slides).
If any clubs are looking for a speaker, I am all in. I learn a lot by giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on
these
PDF slides to others.
de Barry Feierman k3eui
<Nano VNA Analyzer Jan 28.pdf>
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Yes, indeed!! Only us nerdy RF and physics types fully appreciate the tongue-in-cheek humor in those paragraphs. I used to have both his publications (Howard Johnson) and both were autographed. I lost both in a forest fire in 2012. Someone in the local ham community who I used to work with at HP gave me a copy of the book you refer to. But, not autographed. Oh well.............. That book set is golden. Wish more new engineers would read it or at least have it on their reference shelf. Thank you!! Dave - W?LEV On Sat, Jan 30, 2021 at 7:58 PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: Barry,
I thought you might enjoy this description of the resonant swing set by
Graham Johnson in his book . - High Speed Signal Propagation - Advanced
Black Magic (1993).
Roger
-- *Dave - W?LEV* *Just Let Darwin Work*
|
We did, but not the households, cooks, garage mechanics, money shufflers,
civil engineers, and........... Now all our MIL-SPECS and MIL-STANDARDS
contain tables at the end as an Appendix that offer 'conversions' between
metric and 'the king's foot'. I give up.........??
Dave - W?LEV
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Show quoted text
On Sat, Jan 30, 2021 at 10:36 PM Clyde Spencer <cftr01b@...> wrote: Here!! Here!!. We should have been more persistent in the 1960 when the USA
tried to move to the metric system.
*Clyde K. Spencer*
On Sat, Jan 30, 2021 at 5:34 PM David Eckhardt <davearea51a@...>
wrote:
Personally, I'm more at home in metric than our "kings foot" set of units!
However, if I had used metric, all the hams over here in the good 'ol USofA
would bellyache they couldn't deal with 2.54 cm/inch (conversion is on most
calculators) or, heaven forbid, Kelvins instead of degrees F. When
presenting, I warn the audience up-front that miles per hour has no place
in Fields and Waves in specifying c, only 3E8 m/sec and other metric units
shall be used.
Dave - W?LEV
(Born a Nerd, Always a Nerd........)
On Sat, Jan 30, 2021 at 7:24 PM Jean-Denis Muys via groups.io <jdmuys=
[email protected]> wrote:
Very interesting. I was quite shocked that you didn¡¯t use metric units for
the calculations though. This would be my suggestion: use metric units.
JD
On Jan 30, 2021, at 07:23, Barry Feierman <k3euibarry@...> wrote:
?Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club
meetings. I've had my Nano VNA for about four months now, and each
time I
play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE
and
RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy: GRAMPY pushing GRANDCHILD on a swing.
Even little grandkids know that GRAMPY has to push the swing at just the
right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that. If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy
at
just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were
already
in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push
those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we
are
really interested in what the readings are at the ANTENNA junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a 1/4 wavelength of RG213 (6 feet) did
ROTATE the impedance values on the Smith Chart. I "knew" what was
going
to
happen, but still smiled when I saw it with my own eyes. Yet, adding 6
feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR
readings on 10m (28-29 MHz) to the REFLECTION COEFFICIENT, and to the
RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a NANO VNA talk (as pdf slides).
If any clubs are looking for a speaker, I am all in. I learn a lot by
giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on
these
PDF slides to others.
de Barry Feierman k3eui
<Nano VNA Analyzer Jan 28.pdf>
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Progress requires sacrifice (in this case a tiny mental one)
and you should consider that this is not a USA exclusive
group.
toggle quoted message
Show quoted text
On Sat, 30 Jan 2021 at 23:34, David Eckhardt <davearea51a@...> wrote: Personally, I'm more at home in metric than our "kings foot" set of units!
However, if I had used metric, all the hams over here in the good 'ol USofA
would bellyache they couldn't deal with 2.54 cm/inch (conversion is on most
calculators) or, heaven forbid, Kelvins instead of degrees F. When
presenting, I warn the audience up-front that miles per hour has no place
in Fields and Waves in specifying c, only 3E8 m/sec and other metric units
shall be used.
Dave - W?LEV
(Born a Nerd, Always a Nerd........)
On Sat, Jan 30, 2021 at 7:24 PM Jean-Denis Muys via groups.io <jdmuys=
[email protected]> wrote:
Very interesting. I was quite shocked that you didn¡¯t use metric units for
the calculations though. This would be my suggestion: use metric units.
JD
On Jan 30, 2021, at 07:23, Barry Feierman <k3euibarry@...> wrote:
?Hello NANO VNA folks
I keep updating my NANO VNA talk after presenting at different club
meetings. I've had my Nano VNA for about four months now, and each time I
play with it I learn something new.
Questions raised by viewers made me reconsider how to explain PHASE and
RESONANCE and especially what the SMITH CHART reveals.
It feels like PHASE is greatly misunderstood, with antennas.
I tried to come up with a simple mechanical analogy: GRAMPY pushing GRANDCHILD on a swing.
Even little grandkids know that GRAMPY has to push the swing at just
the
right time (PHASE) to increase the amplitude of the kid's swinging.
We all "know" that. If Grampy does not push at the right time, the grandkid complains.
Do antennas work the same way, with the feed line pumping in energy at just the "right time" to increase the current in the antenna?
The rig does not supply the electrons to the antenna (they were already in those copper or aluminum atoms).
The rig supplies, via the feed line, the instructions as to WHEN to push
those electrons.
Think of the feed line like GRAMPY pushing the GRANDKID.
We use the Nano VNA most likely in our (warm) shack. But perhaps we are really interested in what the readings are at the ANTENNA junction.
By changing the feed line by a few feet (on 10 meters) I was able to convince myself that adding about a 1/4 wavelength of RG213 (6 feet) did
ROTATE the impedance values on the Smith Chart. I "knew" what was going to
happen, but still smiled when I saw it with my own eyes. Yet, adding 6
feet of coax (to a 100 ft feed line) did absolutely nothing to the SWR
readings on 10m (28-29 MHz) to the REFLECTION COEFFICIENT, and to the
RETURN LOSS.
So I added these slides to my newest PDF file.
The attachment is my latest rendition of a NANO VNA talk (as pdf slides).
If any clubs are looking for a speaker, I am all in. I learn a lot by giving a talk on a topic (I'm at a 9th grader understanding of the VNA)
73 and TU for all of the helpful suggestions. Feel free to pass on
these
PDF slides to others.
de Barry Feierman k3eui
<Nano VNA Analyzer Jan 28.pdf>
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Nano VNA slide show .... comments on comments
Thank you all for the comments..... feet vs. meters. I had no idea this was going to stir the nest.
Not a big deal, but for those of us taking American exams, it is still antenna lengths in FEET: L = 468/freq for one-half wave.
It just depends on whether you choose to use the speed of light in meter/second or feet/ second .... or feet per NANO second!
It is easy to remember: VELOCITY is about 1 foot per nanosecond
Then worry about the "velocity factor" VF for coax: VF about 0.7 for PE solid insulation and about 0.8 for foam coax dielectric
Answers to questions posed in some slides....
I designed this pdf or PPT slide show to be a discussion, not a one-way lecture.
So when I pose a question (like on the Smith Chart slides) on alive ZOOM conference, I leave time for folks to suggest THEIR answers .... a back-and-forth session.
That's when it gets interesting.
If anyone wants answers to a specific slide, point out the slide number, then tell me YOUR answer. Then I'll respond with my answer.
Each time I give a Nano VNA "Zoom talk" I learn something new. So this is an evolving process.
I still find folks generally are not comfortable with some terms like "Reflection Coefficient" (or the absolute value) and RETURN LOSS and
Smith Charts in polar coordinates frightens most of the Zoom audience.
No one said learning should be "easy" for it takes a while to let a new concept sink in.
I know - I used to teach 9th grade basic PHYSICS as well as university Physics w/calculus.
Reactance is not easy to explain in terms of voltage leading/lagging current ==> so I thought of Grampy pushing Grandchild on a swing as not so threatening.
I appreciate all folks that have written to me off-list.
The Nano VNA is a simple gadget to operate - perhaps more complex to "Interpret" the data.
73 from Philadelphia
Barry k3eui
|
On Sat, Jan 30, 2021 at 05:09 PM, Dragan Milivojevic wrote:
Progress requires sacrifice (in this case a tiny mental one)
and you should consider that this is not a USA exclusive
group.
Progress requires an appreciation of diversity over homogeneity. At least that's what we're told, ad naseum (oops, sorry for the Latin in an English-speaking group!). -- John AE5X
|
On 1/31/21 6:37 AM, Barry Feierman wrote: Nano VNA slide show .... comments on comments
Thank you all for the comments..... feet vs. meters. I had no idea this was going to stir the nest.
Not a big deal, but for those of us taking American exams, it is still antenna lengths in FEET: L = 468/freq for one-half wave. I was curious, because in general, the tests do not require memorizing of specific numbers (except for a few regulatory questions). A quick "grep" of the question pools says that "468" does not appear in them anywhere. In fact, "feet" or "inches" does not occur in the Extra class test (but plenty of "meters" questions, so you'd better know 3E8 m/sec).? I did find one question on the General class test where you'd need to know frequency to feet, but, see below. And that's not a half wavelength in any case (that would be 492 ft). It's a approximately resonant length for a wire antenna. Virtually all of the questions are in terms of relative fractions of a wavelength? (including things like "electrical vs physical length"). I only found one question where you'd need to know that approximate number. For what it's worth, I don't use that number - for me it's easier to remember 300 and work in metric, then convert to feet (.3048 or 3.28, depending on which way you go), and knock off 1-2% for wire antennas. The value sort of shows up here: What is the approximate length for a 1/2 wave dipole antenna cut for 14.250 MHz? (and similar questions for other frequencies). A. 8 feet B. 16 feet C. 24 feet D. 33 feet (answer being D, and the "trap" answer being B, which is about 1/4 wavelength I would do it more by recognizing what "meter" band that frequency is (20 m) and go from there. Half of 20 is 10? meters is about 33 ft (because you know a meter is about 3 feet, and that's the closest answer), and done. As a practical matter, one could not know the conversion (even approximately) and miss that one question, and still pass the test.
|
Barry K3EUI
Roger Need
