Re: VNA and antenna matching : calculating reactance needed to match
Although the ARRL Handbook states, without qualification, that the shunt element always goes on the high-Z side (2021 Handbook, the latest I have), that is strictly true only when the impedances to be matched are real or for a specific range of complex impedances. For a considerable range of complex impedances, there will be multiple solutions to the matching equations and the network may be reversed if necessary or desirable.
This is discussed in detail with GNU Octave code to provide solutions in "More Octave for L-Networks," QEX, May/June, 2012. A graph is provided to determine whether an L-network may be reversed to match a particular pair of complex networks.
73,
Maynard
W6PAP
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On 8/24/23 15:35, W0LEV wrote: Also, know that with L-Networks, the shunt element goes on the high-Z side.
Dave - W?LEV
On Thu, Aug 24, 2023 at 9:49?PM alan victor <avictor73@...> wrote:
Hi Andrew.
You can also apply a formula, use a pencil and paper and a calculator and
obtain a simple
match that will accomplish most Z matches to an antenna.
If you have a representative frequency, S11 and conversion to it's Rs and
Xs values, lets take a look and run an example of your case.
Also, consider looking at this site, very easy to apply:
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If I may ask a follow up questionsabout Nano VNA-H.
1. Is port CH0 input a 50 ohm resistor load?
2. If #1 is correct, would proper attenuator implementation for the port be a series resistor, to form a L pad with the internal resistor?
3. If #2 is correct, would the open-short-load-done-save calibration be done with the measurement plane on the source end of the L pad?
4. If #3 is correct, would scale or another adjustment need to be done to account for a pad between Nano VNA and antenna under test.
btw- the parallel LC "trap" worked at the antenna tower and it reduced the nearby RF source down to less than 100 millivolts. Moving the measurement plane to "cancel out" the trap did not work for me. I was able to obtain presumably credible results by removing the measured impedance of the trap by itself from the measured impedance of the trap and antenna. What concerns me is DC resistance of the trap inductor in series with an antenna that might be 27 ohms at 55 ohms of capacitive or inductive reactance at the operating frequency.
Good news is I have not "blown up" the Nano VNA yet.
Thoughts or suggestions are appreciated. Thank you
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Re: NanoVna H4 Showing blank Screen after updating to latest 1.2.20 firmware
The last FW is the 1.2.24 the last DisLord app version is 1.1.215 now.
This last FWs for H and for the H4 also included the exe file,
(or You can find the dfu-files separately too, - upper on Github... )
Istvaan
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Re: NanoVna H4 Showing blank Screen after updating to latest 1.2.20 firmware
You probably flashed the wrong firmware variant, you used H version
instead of H4 version.
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On Thu, 24 Aug 2023 at 21:04, <john.bachofner@...> wrote:
I recently purchased a NanoVna H4 and found that it had the 1.2.14 firmware. I followed the procedure for downloading the DFU uploading application, then downloaded the firmware. I connected the NanoVna to my computer, placed it into DFU mode, and uploaded the firmware through the App (successfully according to the App). I then disconnected the USB and turned off the NanoVna. When I tried to turn it back on, I get a blank screen. It is fully charged and I have tried to repeat the upload in case there was an error. However, I just get a blank screen,
Anyone have any ideas on how to fix this issue? I suppose I could go back to the 1.2.14 firmware if I could find it. I would prefer to be using the latest firmware.
Thank you in advance for any assistance.
John R. Bachofner
KJ7AOL
John.bachofner@...
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Re: VNA and antenna matching : calculating reactance needed to match
On Thu, Aug 24, 2023 at 12:46 PM, Andrew (G1RVD G0Z) wrote:
Let's say one measures the impedance of an antenna, reading the S11 parameters
from the NanoVNA via USB, converting the reflection coefficients to real &
imaginary impedances (thank you Rich NE1EE for your spreadsheet). Does
anyone have a spreadsheet to calculate the necessary reactance (L C) that
needs to be added in a L match tuner (with series L)? Effectively, a
spreadsheet, or formula, that replicates what one would normally use a Smith
chart to achieve.
A couple of things to consider: - When you say "measure the impedance of the antenna" in this case you are really measuring the impedance at the end of the coax feedline. It will be much different at the antenna feedpoint. - Make sure that you don't have any current flowing on the outer surface of the shield (the "3rd wire"). This usually requires a balun or RF choke ("isolator"). If you don't do this the measured impedance will change when you connect the USB cable which has a ground shield on it. You can check by measuring the impedance on the NanoVNA with and without the USB cable attached. - There is a LC match feature in recent DiSlord firmware for the NanoVNA - If you have a copy of the ARRL Antenna Book the CD comes with a program called TLW that will design various type of tuners and gives their matching efficiency. - Here is an online LC match calculator: Roger
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Re: VNA and antenna matching : calculating reactance needed to match
Also, know that with L-Networks, the shunt element goes on the high-Z side.
Dave - W?LEV
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On Thu, Aug 24, 2023 at 9:49?PM alan victor <avictor73@...> wrote: Hi Andrew.
You can also apply a formula, use a pencil and paper and a calculator and
obtain a simple
match that will accomplish most Z matches to an antenna.
If you have a representative frequency, S11 and conversion to it's Rs and
Xs values, lets take a look and run an example of your case.
Also, consider looking at this site, very easy to apply:
-- *Dave - W?LEV*
--
Dave - W?LEV
|
Re: VNA and antenna matching : calculating reactance needed to match
Hi Andrew.
You can also apply a formula, use a pencil and paper and a calculator and obtain a simple
match that will accomplish most Z matches to an antenna.
If you have a representative frequency, S11 and conversion to it's Rs and Xs values, lets take a look and run an example of your case.
Also, consider looking at this site, very easy to apply:
|
Re: VNA and antenna matching : calculating reactance needed to match
SimSmith includes various matching topologies as part of the Smith Chart presentation: Dave - W?LEV On Thu, Aug 24, 2023 at 7:46?PM Andrew (G1RVD G0Z) <andrew@...> wrote: Hello,
Having read through the Group, I've not been able to find an answer to my
question, but I have found a lot of information that suggests several
members of the Group will know ... here's the question:
Let's say one measures the impedance of an antenna, reading the S11
parameters from the NanoVNA via USB, converting the reflection coefficients
to real & imaginary impedances (thank you Rich NE1EE for your
spreadsheet). Does anyone have a spreadsheet to calculate the necessary
reactance (L C) that needs to be added in a L match tuner (with series L)?
Effectively, a spreadsheet, or formula, that replicates what one would
normally use a Smith chart to achieve.
Thanks in advance.
-- *Dave - W?LEV* -- Dave - W?LEV
|
Re: VNA and antenna matching : calculating reactance needed to match
Hi Andrew
For me, SimSmith/SimNEC is the right software to do those calculations.
Very helpfull.
73 - Antonio EA7HJ
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VNA and antenna matching : calculating reactance needed to match
Hello,
Having read through the Group, I've not been able to find an answer to my question, but I have found a lot of information that suggests several members of the Group will know ... here's the question:
Let's say one measures the impedance of an antenna, reading the S11 parameters from the NanoVNA via USB, converting the reflection coefficients to real & imaginary impedances (thank you Rich NE1EE for your spreadsheet). Does anyone have a spreadsheet to calculate the necessary reactance (L C) that needs to be added in a L match tuner (with series L)? Effectively, a spreadsheet, or formula, that replicates what one would normally use a Smith chart to achieve.
Thanks in advance.
|
NanoVna H4 Showing blank Screen after updating to latest 1.2.20 firmware
I recently purchased a NanoVna H4 and found that it had the 1.2.14 firmware. I followed the procedure for downloading the DFU uploading application, then downloaded the firmware. I connected the NanoVna to my computer, placed it into DFU mode, and uploaded the firmware through the App (successfully according to the App). I then disconnected the USB and turned off the NanoVna. When I tried to turn it back on, I get a blank screen. It is fully charged and I have tried to repeat the upload in case there was an error. However, I just get a blank screen,
Anyone have any ideas on how to fix this issue? I suppose I could go back to the 1.2.14 firmware if I could find it. I would prefer to be using the latest firmware.
Thank you in advance for any assistance.
John R. Bachofner
KJ7AOL
John.bachofner@...
|
Re: some Nano VNA SAVER 40m antenna graphs
Thanks, Jim. As you have likely gathered by now from my (too many) posts,
in retirement I'm into promoting the hard sciences and math to the HS bunch
and helping others learn the finer points of all things RF. Yes, I will
contact Dr. Iyer. Thank you so much for the reference!
Dave - W?LEV
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On Thu, Aug 24, 2023 at 4:39?PM Jim Lux <jimlux@...> wrote: On 8/24/23 8:09 AM, W0LEV wrote:
Excellent work, Barry. I've always contended introduction of the NANOVNAs
would be an outstanding tool for learning. You've proved that. The
universities ought to be buying these in the 100s to teach what you have
learned.
Dave - W?LEV
The universities *are* buying these by the dozen.
Prof Ashwin Iyer at University of Alberta used them in a "intro class"
along with a VOM (ECE 478) a bunch of parts and modules, etc. Even a
soldering iron. During COVID isolation.
They had a great experience.
Might be behind a paywall
A. K. Iyer, B. P. Smyth, M. Semple and C. Barker, "Going Remote:
Teaching Microwave Engineering in the Age of the Global Pandemic and
Beyond," in IEEE Microwave Magazine, vol. 22, no. 11, pp. 64-77, Nov.
2021, doi: 10.1109/MMM.2021.3102649.
They did a great job. They had multiple resources, TAs who could
explain on a one-to-one basis, etc.
If you want to pursue more info, Prof Iyer would probably be happy to
talk to you.
Prof. Ashwin K. Iyer <iyer@...>
-- *Dave - W?LEV*
--
Dave - W?LEV
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Re: some Nano VNA SAVER 40m antenna graphs
On 8/24/23 8:09 AM, W0LEV wrote: Excellent work, Barry. I've always contended introduction of the NANOVNAs
would be an outstanding tool for learning. You've proved that. The
universities ought to be buying these in the 100s to teach what you have
learned.
Dave - W?LEV
The universities *are* buying these by the dozen. Prof Ashwin Iyer at University of Alberta used them in a "intro class" along with a VOM (ECE 478) a bunch of parts and modules, etc. Even a soldering iron. During COVID isolation. They had a great experience. Might be behind a paywall A. K. Iyer, B. P. Smyth, M. Semple and C. Barker, "Going Remote: Teaching Microwave Engineering in the Age of the Global Pandemic and Beyond," in IEEE Microwave Magazine, vol. 22, no. 11, pp. 64-77, Nov. 2021, doi: 10.1109/MMM.2021.3102649. They did a great job. They had multiple resources, TAs who could explain on a one-to-one basis, etc. If you want to pursue more info, Prof Iyer would probably be happy to talk to you. Prof. Ashwin K. Iyer <iyer@...>
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Re: some Nano VNA SAVER 40m antenna graphs
Excellent work, Barry. I've always contended introduction of the NANOVNAs
would be an outstanding tool for learning. You've proved that. The
universities ought to be buying these in the 100s to teach what you have
learned.
Dave - W?LEV
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On Thu, Aug 24, 2023 at 12:37?PM Barry K3EUI <k3euibarry@...> wrote: What I found reassuring is that the four graphs (on all three antennas)
all agree with each other!
The RETURN LOSS (dB) is sharp (yes, I plot it as a negative value) showing
the reflections are least (greatest return loss) where the SWR is lowest,
and where the PHASE graph crosses ZERO degrees, and also where the Smith
Chart is closest to the Bull¡¯s Eye.
Now ¡°matching¡± makes more sense to me.
Any one graph predicts the others.
I passed all of these ham radio tests (teenager) without really
understaning any of these graphs.
Now (I think) I understand the relationships.
the Nano VNA forced me to really learn what these concepts are all about.
TU VNA SAVER author
de k3eui barry
-- *Dave - W?LEV*
--
Dave - W?LEV
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Donald,
I'm not sure I can get the resolution necessary from the "far" end. The cable is 100m long and the fault is about 240mm from the "near" end.
Geoff
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On 8/23/2023 4:07 PM, Donald S Brant Jr wrote: On Wed, Aug 23, 2023 at 04:52 PM, Geoff Peters - AB6BT wrote:
So the question is...can I trust that number?
Measure from the other end and see if the two results add up to the correct total length. If they do you can at least have better confidence. If they doi not you know there is a problem.
73, Don N2VGU
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Re: some Nano VNA SAVER 40m antenna graphs
What I found reassuring is that the four graphs (on all three antennas) all agree with each other!
The RETURN LOSS (dB) is sharp (yes, I plot it as a negative value) showing the reflections are least (greatest return loss) where the SWR is lowest, and where the PHASE graph crosses ZERO degrees, and also where the Smith Chart is closest to the Bull¡¯s Eye.
Now ¡°matching¡± makes more sense to me.
Any one graph predicts the others.
I passed all of these ham radio tests (teenager) without really understaning any of these graphs.
Now (I think) I understand the relationships.
the Nano VNA forced me to really learn what these concepts are all about.
TU VNA SAVER author
de k3eui barry
|
Bob,
Thanks for that.
Yes, I have measured the skew, because of the twists per inch (pitch?) the tighter the twist the longer the wire physical length as well. I read that a maximum of 50nS/100 meters was the limit that the hardware was able to correct.
But for sure you can measure the difference.
Geoff
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On 8/23/2023 5:02 PM, Bob Ecclestone VK2ZRE wrote: Hi Geoff,
You probably already know this, but each pair in a Cat6 cable has a different "twist rate" to minimise crosstalk, so the VF for each pair will be slightly different.
Try it with a piece of scrap cable. Measure the electrical length of each pair, you will find it will be slightly different for each pair.
I was involved with a startup VDSL broadband internet provider in the early 2000s and we used custom made, multiple pair Cat5 cable for the "last mile" (10, 25, 50 & 100pr).
We ended up characterising each pair in each cable size to help with fault finding. As with coax, the VF varied slightly along a cable and across batches, but it got us in the ball park to locate a fault.
Cheers...Bob VK2ZRE
On 24/08/2023 7:14 am, Geoff Peters - AB6BT wrote:
Sigi,
Yes, I have a piece of CAT6 cable to test. I removed the jacket at 1 foot intervals for about an inch. I will test by cutting 1 wire at a time at each location and see what I measure.
Geoff
On 8/23/2023 2:02 PM, Siegfried Jackstien wrote:
take 10 inch of speaker wire.. that should show almost similar numbers.. if thats the case then yes you can trust it
dg9bfc sigi
Am 23.08.2023 um 22:52 schrieb Geoff Peters - AB6BT:
Roger,
I sent a reply but it hasn't shown up so here's take 2...
In this case, what I'm trying to determine is the minimum distance I can measure to a fault.. I used 4.8mm to simplify this discussion, I'm not sure what you mean by "only in steps of 1 so this is the limiting factor." . I understand that the actual distance/step is VF dependent.
For example, I have a CAT6 cable with an open green wire. I have calculated the VF as I know the physical length of the cable, 300 feet/91.44 meters.
Using a NanoVNA-H4 I measure the distance to the fault at about 240mm.
So the question is...can I trust that number?
Geoff
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Hi Geoff,
You probably already know this, but each pair in a Cat6 cable has a different "twist rate" to minimise crosstalk, so the VF for each pair will be slightly different.
Try it with a piece of scrap cable. Measure the electrical length of each pair, you will find it will be slightly different for each pair.
I was involved with a startup VDSL broadband internet provider in the early 2000s and we used custom made, multiple pair Cat5 cable for the "last mile" (10, 25, 50 & 100pr).
We ended up characterising each pair in each cable size to help with fault finding. As with coax, the VF varied slightly along a cable and across batches, but it got us in the ball park to locate a fault.
Cheers...Bob VK2ZRE
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On 24/08/2023 7:14 am, Geoff Peters - AB6BT wrote: Sigi,
Yes, I have a piece of CAT6 cable to test. I removed the jacket at 1 foot intervals for about an inch. I will test by cutting 1 wire at a time at each location and see what I measure.
Geoff
On 8/23/2023 2:02 PM, Siegfried Jackstien wrote:
take 10 inch of speaker wire.. that should show almost similar numbers.. if thats the case then yes you can trust it
dg9bfc sigi
Am 23.08.2023 um 22:52 schrieb Geoff Peters - AB6BT:
Roger,
I sent a reply but it hasn't shown up so here's take 2...
In this case, what I'm trying to determine is the minimum distance I can measure to a fault.. I used 4.8mm to simplify this discussion, I'm not sure what you mean by "only in steps of 1 so this is the limiting factor." . I understand that the actual distance/step is VF dependent.
For example, I have a CAT6 cable with an open green wire. I have calculated the VF as I know the physical length of the cable, 300 feet/91.44 meters.
Using a NanoVNA-H4 I measure the distance to the fault at about 240mm.
So the question is...can I trust that number?
Geoff
|
Right, yes, I know the VF is independent of length.
The test has nothing to do with determining VF. I have already done that with a piece of known physical length.
The test I have set up is a piece of CAT cable. I have removed the jacket at 1 foot intervals. I will cut 1 conductor starting at the 1 foot mark and see what length the NanoVNA shows for the fault. I'll reconnect the wire I cut and repeat the process at 1 foot intervals to see how the physical length numbers compare with the measured numbers.
Geoff
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On 8/23/2023 3:50 PM, Roger Need via groups.io wrote: On Wed, Aug 23, 2023 at 03:10 PM, Geoff Peters - AB6BT wrote:
OK, I see what you mean, and I suspect the the VF can vary by 1% over the
length of the cable.
I will test with a piece of CAT6 by cutting one wire and reconnecting at one
foot intervals.
The VF for the TDR test will be the same no matter what length you cut the CAT6 cable. VF for a specific type of cable will vary by manufacturer and even different between production runs by the same manufacturer. But for what you are measuring this should not be a concern. Take a measured length and then adjust VF to get the same calculated length using the TDR. Then you have the VF to use for with that specific type of cable.
Roger
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On Wed, Aug 23, 2023 at 04:52 PM, Geoff Peters - AB6BT wrote:
So the question is...can I trust that number?
Measure from the other end and see if the two results add up to the correct total length. If they do you can at least have better confidence. If they doi not you know there is a problem. 73, Don N2VGU
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Roger Need
Barry K3EUI
Donald S Brant Jr