Re: Nano VNA Prt I Basics: Part II Under the Hood de k3eui
#video
Hope, We have this video again.
Luis T.
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El vie., 16 jul. 2021 9:04, Barry K3EUI <k3euibarry@...> escribi¨®: HELLO ALL
As of July 16th:
I gave the Nano VNA talk in two installments to the Leicester Radio
Society (UK) but I did not record it and I did not post it. I'll contact
the person who did post it and see what happened to it.
I only reference this (recorded) video as the latest talk I have given on
the Nano VNA
Part I was the basic stuff - very low math but I do mention Smith Chart
I treat the nano VNA as just another tool in your ham radio toolkit
I show how you can use the Nano VNA to check out coax, filters, and
antennas.
All of the graphs were produced by NANO VNA SAVER software (free,
Win 10).
THANK YOU to the author of that app.
Part II Uner the Hood - looks at all of the measurements and calculated
parameters in more detail.
You can Calibrate the Nano VNA via software (Nano VNA SAVER) and do a
lot more with the tool.
I then go into gory detail about the Smith Chart - but not assuming
one is already familiar with it.
Part II ends with looking at resistance, reactance, and impedance and
how these plot on Smith Charts.
How do antenna tuners "cancel" the reactance on your feedline by
introducig a CONJUGATE match?
There is a bit of magic and fancy math, but I try to avoid that.
Warning: there is a Smith Chart quiz in the talk and in the PDF.
Conclusion: antennas do not "need to be resonant" to work well
(i.e. 43 ft vertical) but the entire antenna system (including feed line)
needs to present a reasonable load to your rig. The typical SWR meter gives
you a reading (2:1) but gives no information as to what you can do to
improve your antenna.
Thus, the Nano VNA is a much better "tool" at analyzing your antenna than
a mere SWR meter.
This is the best I've been able to do and explain (as a non-engineer)
after one year experience with VNA.
If I can get it posted again, feel free to share both the video and the
extended PDF with others.
This has been and continues to be a learning challenge for me.
There are many ways to "see" a concept. I'm looking for a 9th grade level
right now.
I hope my video Zoom and the PDF is aiming at the right audience.
73
K3EUI Barry
Philadelphia
K3euibarry@...
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Re: Resistor measurements
On 7/16/21 8:12 AM, Zack Widup wrote: I found this fascinating. I need to make an attenuator for my FT817 on
transmit as a 432 MHz
microwave IF radio. I have the appropriate carbon-film resistors. I
measured them on my NanoVNA to see what they measure at 432 MHz. This is
something I never could do before I had a NanoVNA. Two 200 ohm 1 watt
resistors measure 198 ohms on my DVM. The NanoVNA measures 198 ohms up to
about 500 kHz, and then the resistance starts to climb. At 432
MHz they both measure 225 ohms with a small amount of inductance (12 nH). I
measured a 68 ohm carbon-film resistor with similar results - it measures
67.5 ohms with the DVM and the NanoVNA up to about 500 kHz. At 432 MHz it
measures 86 ohms and a small inductance. I measured a 100 ohm carbon
composition resistor. It measured 102 ohms on the DVM and with the NanoVNA
up to about 1 MHz. The resistance barely changed on the NanoVNA above that.
At 432 MHz it measured 106 ohms. Yes, the NanoVNA opens up a whole new world of "hands on understanding" of things like parasitic L and C.? It's an amazing device for this.
I kind of figured the carbon film resistors weren't as accurate at VHF/UHF
frequencies compared to carbon composition resistors. This verified it.
Probably a skin effect problem.
And, thus, one begins diving into the rabbit hole <grin>
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I found this fascinating. I need to make an attenuator for my FT817 on
transmit as a 432 MHz
microwave IF radio. I have the appropriate carbon-film resistors. I
measured them on my NanoVNA to see what they measure at 432 MHz. This is
something I never could do before I had a NanoVNA. Two 200 ohm 1 watt
resistors measure 198 ohms on my DVM. The NanoVNA measures 198 ohms up to
about 500 kHz, and then the resistance starts to climb. At 432
MHz they both measure 225 ohms with a small amount of inductance (12 nH). I
measured a 68 ohm carbon-film resistor with similar results - it measures
67.5 ohms with the DVM and the NanoVNA up to about 500 kHz. At 432 MHz it
measures 86 ohms and a small inductance. I measured a 100 ohm carbon
composition resistor. It measured 102 ohms on the DVM and with the NanoVNA
up to about 1 MHz. The resistance barely changed on the NanoVNA above that.
At 432 MHz it measured 106 ohms.
I kind of figured the carbon film resistors weren't as accurate at VHF/UHF
frequencies compared to carbon composition resistors. This verified it.
Probably a skin effect problem.
73, Zack W9SZ
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It is important to remember that "accuracy" and "precision" are two separate characteristics of any measurement.
DaveD
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On 7/16/2021 11:02 AM, Donald S Brant Jr wrote: The need for calibration and how frequently, varies with the measurement. If you need great precision, like accurately measuring a 40-db return loss, you might need to carefully calibrate several times a day. If you only need to know the frequency of an S11 dip, like tuning a small loop antenna in the field where there is only a single adjustment, you don't even need to calibrate at all.
73, Don N2VGU
--
This email has been checked for viruses by Avast antivirus software.
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The need for calibration and how frequently, varies with the measurement. If you need great precision, like accurately measuring a 40-db return loss, you might need to carefully calibrate several times a day. If you only need to know the frequency of an S11 dip, like tuning a small loop antenna in the field where there is only a single adjustment, you don't even need to calibrate at all.
73, Don N2VGU
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I always do the calibration with the NanoVNA by itself, not connected to a computer. I have saved several band segments that I frequently use (say, 45 to 55 MHz, 140 to 150 MHz, 420 to 450 MHz) with the calibration done for each of those segments and, for what I do, I haven't needed to re-calibrate each time. 73, Zack W9SZ On Thu, Jul 15, 2021 at 12:37 PM Richard Clemens <rich.clemens@...> wrote: On Thu, Jul 15, 2021 at 09:27 AM, Jim Lux wrote:
Very helpful -- however when I do a calibration with nanovna-saver's tool
it does not ask for a frequency range when starting the process -
confusion...
2) If the frequency span of the measurements is different than the
frequency
span of the calibration. The NanoVNA does some interpolation, but if you did
a cal from 0-50 MHz and now you're measuring a DUT from 200-300 MHz, the
measurement might be iffy. Likewise if you did a cal from 0-900 MHz, and the
measurement is from 20-30 MHz.
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That doesn¡¯t address the point.
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Re: Nano VNA Prt I Basics: Part II Under the Hood de k3eui
#video
HELLO ALL
As of July 16th:
I gave the Nano VNA talk in two installments to the Leicester Radio Society (UK) but I did not record it and I did not post it. I'll contact the person who did post it and see what happened to it.
I only reference this (recorded) video as the latest talk I have given on the Nano VNA
Part I was the basic stuff - very low math but I do mention Smith Chart
I treat the nano VNA as just another tool in your ham radio toolkit
I show how you can use the Nano VNA to check out coax, filters, and antennas.
All of the graphs were produced by NANO VNA SAVER software (free, Win 10).
THANK YOU to the author of that app.
Part II Uner the Hood - looks at all of the measurements and calculated parameters in more detail.
You can Calibrate the Nano VNA via software (Nano VNA SAVER) and do a lot more with the tool.
I then go into gory detail about the Smith Chart - but not assuming one is already familiar with it.
Part II ends with looking at resistance, reactance, and impedance and how these plot on Smith Charts.
How do antenna tuners "cancel" the reactance on your feedline by introducig a CONJUGATE match?
There is a bit of magic and fancy math, but I try to avoid that.
Warning: there is a Smith Chart quiz in the talk and in the PDF.
Conclusion: antennas do not "need to be resonant" to work well (i.e. 43 ft vertical) but the entire antenna system (including feed line) needs to present a reasonable load to your rig. The typical SWR meter gives you a reading (2:1) but gives no information as to what you can do to improve your antenna.
Thus, the Nano VNA is a much better "tool" at analyzing your antenna than a mere SWR meter.
This is the best I've been able to do and explain (as a non-engineer) after one year experience with VNA.
If I can get it posted again, feel free to share both the video and the extended PDF with others.
This has been and continues to be a learning challenge for me.
There are many ways to "see" a concept. I'm looking for a 9th grade level right now.
I hope my video Zoom and the PDF is aiming at the right audience.
73
K3EUI Barry
Philadelphia
K3euibarry@...
|
Re: Capturing and saving measurements
NanoVNASaver also uses heuristics for NanoVNA V2plus4:
this might be worth including in the SimSmith utility as well
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Re: Capturing and saving measurements
thanks, DiSlord. Once I changed bandwidth to 4kHz on NanoVNA H4 then SimSmith connects/interacts with the device.
I tried both 101/401 data points and both settings are okay.
Still no luck with the NanoVNA V2plus4 though
I checked with NanoVNASaver and indeed timeout handling is made dependent on bandwidth and #data points:
and:
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50 ohm PL259 O239 connectors are readily available. Agree that if the discontinuity is very short compared to a 1/4 wave it make little/no difference. Going from a 50 ohms, through a 30 ohm PL259, and then back into a 50 ohms, the reflection from 50 into 30 is opposite and equal to that from 30 into 50. If the distance between them is very short compared to 1/4 wavelength, they essentially cancel. A PL259 it's maybe a cm or two compared to 250 cm for a 1/4 wavelength at 10m.
You can look inside HF amplifiers, tuners and other HF equipment and see RF being conducted around inside with simple wires, not transmission lines. That works because the lengths are short compared the the wavelengths involved.
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Re: Capturing and saving measurements
I can connect SimSmith vs my NanoVNA H4
SimSmith use old data exchange format, and not allow get data if set low bandwidth setting on Nano (need more big timeout)
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Look at W2AEW YouTube channel I think he did a video on this.
73
Fred KB4QZH
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On 7/16/21 12:16 AM, James Balagtas wrote: Hi guys
Wonder if you can acctually cut an exact 1/2 wave coax for a given freq without getting VF and math usong nano VNA. It woukd be very useful when making 4:1 balun with better accuracy rather than estimating with math. Very easy - cal the vna, hook up your coax, look at the *phase* of S11.? Cut until the phase is zero degrees at your frequency of interest.? Your cable is a multiple of half wavelengths. 180 degrees phase shift on the way out, reflection from the open (which does not flip the phase, like a short does), 180 degree phase shift on the way back, so the net is zero degrees. The magnitude of S11 is twice the cable loss. If you want a 1/4 wave stub, go for 180 degrees. 90 degrees on the way out, reflect, 90 degrees on the way back. I also need it for duplexer pigtails.
Ive been searching in youtube if soneone ever did a video.
Thanks more power
DW3JBX
James
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Forgot one important note. Trim the coax stub until the dip is at the
desired frequency.
*Clyde K. Spencer*
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On Fri, Jul 16, 2021 at 7:55 AM Clyde Spencer <cftr01b@...> wrote: You can try this process.
[image: image.png]
*Clyde K. Spencer*
On Fri, Jul 16, 2021 at 4:15 AM James Balagtas <jbx907@...> wrote:
Hi guys
Wonder if you can acctually cut an exact 1/2 wave coax for a given freq
without getting VF and math usong nano VNA. It woukd be very useful when
making 4:1 balun with better accuracy rather than estimating with math.
I also need it for duplexer pigtails.
Ive been searching in youtube if soneone ever did a video.
Thanks more power
DW3JBX
James
|
You can try this process.
[image: image.png]
*Clyde K. Spencer*
toggle quoted message
Show quoted text
On Fri, Jul 16, 2021 at 4:15 AM James Balagtas <jbx907@...> wrote: Hi guys
Wonder if you can acctually cut an exact 1/2 wave coax for a given freq
without getting VF and math usong nano VNA. It woukd be very useful when
making 4:1 balun with better accuracy rather than estimating with math.
I also need it for duplexer pigtails.
Ive been searching in youtube if soneone ever did a video.
Thanks more power
DW3JBX
James
|
Re: Capturing and saving measurements
On Wed, Jul 14, 2021 at 03:04 PM, ward harriman wrote: This utility can be used to connect to, calibrate, initiate measurements,
write touchstone files, and import them for further analysis. I have used NanoVNASaver and SimSmith earlier this year to construct the output matching network of a DIY BS170 small signal amplifier. This required constant switching between NanoVNASaver (to measure) and SimSmith (to analyze). Doing all this from within SimSmith will be a big time-saver and streamline the process. I even noticed that one can apparently define the value of the calibration load to a value other than 50 ohm. That being said: I tried to get the latest SimSmith running under both Windows 10 Pro and Ubuntu 20 LTS. On both OSes I have no issue connecting to the NanoVNA (both -H4 with latest Dislord firmware and newest V2plus4 w/ stock firmware) with NanoVNASaver but I'm unable to connect with SimSmith. I can see and select the serial port from the drop down list but then it always after a small time reports 'Connection Lost'. On Ubuntu I see a Java exception 'serialStuff.SerialException: Serial Port Timeout' in serialStuff.Utils.getDataLines(Utils.java:150) which seems to originate from nanoVNA.Dialog.probePort(Dialog.java:493). The selected serial port remains with a red background in SimSmith. Is this an issue with EOL character differences between Windows/Linux vs. Mac? Did others have more luck? I really want this to work ... Uwe.
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Hi guys
Wonder if you can acctually cut an exact 1/2 wave coax for a given freq without getting VF and math usong nano VNA. It woukd be very useful when making 4:1 balun with better accuracy rather than estimating with math.
I also need it for duplexer pigtails.
Ive been searching in youtube if soneone ever did a video.
Thanks more power
DW3JBX
James
|
Re: Nano VNA Prt I Basics: Part II Under the Hood de k3eui
#video
It looks like the file in that One Drive folder has been deleted. It was good when I downloaded it yesterday. I have a copy of it on my hard-drive but it's almost 3GB. Too big to email and I don't have enough room on my OneDrive account to move it there where I could share it.
Hopefully, Barry will see this and reload it where everyone can get to it again.
--
*Don - W3DRM*
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Re: Nano VNA Prt I Basics: Part II Under the Hood de k3eui
#video
I had the same thing happen On Thu, Jul 15, 2021 at 8:55 PM Josh Kuperman <josh.kuperman@...> wrote: On Wed, Jul 14, 2021 at 09:49 PM, W3DRM - Don wrote:
I started watching the video this morning and made it through the very
basic but good explanation of smith charts; then I ran some errands and
started watching again and after 5 minutes the video vanished.
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Donald S Brant Jr
Richard Clemens
Barry K3EUI
Lou W7HV
James Balagtas
W7DRM - Don
David Nelson