On Sun, Jul 17, 2022 at 01:17 PM, <cariboome@...> wrote: My question is: for some tuning, I often show a very low SWR (<1:1.05) with a
logmag reading of -15 or thereabouts, and another tune showing about the same
SWR but a logmag of -40, -50 or even -90 dB. The logmag trace sometimes
appearing as a very steep and deep notch, often at or in the SWR trace and
other times just a shallow dip. The Smith typically shows a fairly consistent
50 ohms plus or minus 1 or 2 at tuned resonance. Is this a representation of
reflected loss and VSWR being shown real time side by side? Is it better to
have a logmag reading of -90 dB let's say, as well as a very low SWR -- vs
very low SWR and a "higher" logmag of -20dB for instance?
Yes side-by-side as you put it.. The NanoVNA is calculating all the parameters (SWR, Return Loss (logmag format) and impedance (R, X) from the same scanned measurements. If your return loss is 14 dB you have a VSWR of about 1.5 which is fine for most purposes. If your SWR is higher than this modern solid state transmitters tend to cut back on their power output. A VSWR of 1.1 is a RL of 26 dB and that is excellent. Here is a link to a table of VSWR vs Return Loss. It also shows the reflected and through power. You should also be aware that Return Loss is a positive number but many publications use a negative sign which is not correct but done anyway. Yes confusing but the way it is... Roger
|
Good day. I'm fairly new to both amateur radio and this marvelous device, the NanoVNA H4 v4.3 sold by Seesii on Amazon.ca
I find tuning my many inverted V antennas using a manual tuner extremely effective using this Nanovna -- set to s11 on 3 parameters for logmag, Smith and SWR traces.
My question is: for some tuning, I often show a very low SWR (<1:1.05) with a logmag reading of -15 or thereabouts, and another tune showing about the same SWR but a logmag of -40, -50 or even -90 dB. The logmag trace sometimes appearing as a very steep and deep notch, often at or in the SWR trace and other times just a shallow dip. The Smith typically shows a fairly consistent 50 ohms plus or minus 1 or 2 at tuned resonance. Is this a representation of reflected loss and VSWR being shown real time side by side? Is it better to have a logmag reading of -90 dB let's say, as well as a very low SWR -- vs very low SWR and a "higher" logmag of -20dB for instance?
I sincerely hope I'm expressing myself sensibly...
--
- Dave
-VA7WNW-
|
Re: Using VNA to test NFC tags
On 7/17/22 6:17 AM, Larry Martin wrote: I work with RFID/NFC at 13.56 MHz, and have been using my NanoVNA with a nonresonant loop to check the resonant frequency of HF tags. I'm wondering if the radio experts here can tell me if other measurements are reasonable. Here is the setup (172KB jpeg):
The top picture shows the loop with nothing on it, a near perfect short with a little inductance. The bottom view shows the loop with a typical NFC inlay on top. Resonant frequency is a little high. That's the only objective measure I can really define with this setup.
I would love to be able to point to the depth of the LOGMAG traces as some kind of inlay strength indicator. Informally, I like to compare incoming tags with the one in the link to see if it has as-good LOGMAG deflection (this tag type is the best so far), but I can't convince anyone else of anything based on that observation. I'm wondering if someone with more radio knowledge can think of a way to make a sensitivity measurement out of that, so I could tell my customers whether they are getting good tags from their vendors.
What you're sort of measuring here is a combination of the coupling to the tag, and the mismatch of the load on the tag. Think of the equivalent circuit as being a transformer (your loop and the loop on the tag) coupled to some load. So the "mismatch" you see in the S11 is a combination of the coupling ratio and the actual load. The actual load may or may not be 50 ohms in the design circuit. Since the receiver and transmitter are typically connected right to the tag's antenna, traditional "matched transmission line" might not be relevant. You might be able to set up a test rig to do incoming inspection on theoretically identical tags (same make and model) - whatever the mismatch and frequency is, it should be the same. But it's not necessarily a good way to compare different kinds of tags. Maybe one mfr designs for 150 ohms and another designs for 50 ohms and yet another designs for 10 ohms. Couple notes:
* this works with _some_ EMI field probes.
* this also works at UHF (902-928 MHz), with _a few_ field probes.
* I know there is test equipment for this, $25k and up.
|
Re: Antenna VNA comparison with manufacturer
Try placing the antenna in a different location.... far away from anything metal/magnetic... - such items could be detuning the antenna... also, try using a longer test cable, so as to keep the VNA away from the antenna...say 5 feet or so, being sure to re-calibrate with the longer test cable...
Brian - KI8KY
|
toggle quoted message
Show quoted text
It should have 3 calibration plugs, open, shorted, and 50-ohm. If the shorted plug is missing, contact the distributor asap and request one. -- Rich WB2GXM------ Original message------From: ObserverDate: Sun, Jul 17, 2022 3:39 AMTo: [email protected];Cc: Subject:[nanovna-users] missing sma #adaptersMy newly received nanovna, has only two test connectors, plus two leads and the pen. Do they expect me to make the missing short circuit connector, myself ? It may seem a silly question, but, I am a totally newbie , nerd .
|
another silly mistake !
I didnt realise that the short circuit cap is actually screwed in on the Ch0 and CH1 !!!
|
Using VNA to test NFC tags
I work with RFID/NFC at 13.56 MHz, and have been using my NanoVNA with a nonresonant loop to check the resonant frequency of HF tags. I'm wondering if the radio experts here can tell me if other measurements are reasonable. Here is the setup (172KB jpeg):
The top picture shows the loop with nothing on it, a near perfect short with a little inductance. The bottom view shows the loop with a typical NFC inlay on top. Resonant frequency is a little high. That's the only objective measure I can really define with this setup.
I would love to be able to point to the depth of the LOGMAG traces as some kind of inlay strength indicator. Informally, I like to compare incoming tags with the one in the link to see if it has as-good LOGMAG deflection (this tag type is the best so far), but I can't convince anyone else of anything based on that observation. I'm wondering if someone with more radio knowledge can think of a way to make a sensitivity measurement out of that, so I could tell my customers whether they are getting good tags from their vendors.
Couple notes:
* this works with _some_ EMI field probes.
* this also works at UHF (902-928 MHz), with _a few_ field probes.
* I know there is test equipment for this, $25k and up.
|
Hi,
Check what you ordered, what should have been included, parts might be missing.
Typically, 4 calibration components supplied with the nanoVNA.
If this is not a supply problem, calibration kits are available, for example
Kind regards
Ed
|
You may decide that for yourself.
Anything goes. :-)
Op 17-7-2022 om 09:38 schreef Observer:
toggle quoted message
Show quoted text
My newly received nanovna, has only two test connectors, plus two leads and the pen.
Do they expect me to make the missing short circuit connector, myself ?
It may seem a silly question, but, I am a totally newbie , nerd .
|
My newly received nanovna, has only two test connectors, plus two leads and the pen.
Do they expect me to make the missing short circuit connector, myself ?
It may seem a silly question, but, I am a totally newbie , nerd .
|
Re: Antenna VNA comparison with manufacturer
Think "terminal velocity" . . .
toggle quoted message
Show quoted text
On July 16, 2022 9:06:38 PM EDT, Jim Shorney <jimNU0C@...> wrote:
The worst were car stereo amplifier output Watts. Still trying to figure out how they got 300W out of a 12W chip....
73
-Jim
NU0C
On Sat, 16 Jul 2022 16:56:28 -0400
"Doug" <jdkearney@...> wrote:
Or GMRS radio range!
Doug? -? VA3DKA
On 16/07/2022 16:20, W0LEV wrote:
Remember, marketing has the last word when a product is finally released
for sale. Also, manufacturing variations also play into the whole
picture. I wouldn't be too concerned with anything less than 2:1.
Suppliers can claim anything. Take a look at the gain figures quoted by
the many suppliers of CB antennas. They are outrageous and have no
connection to reality!!!
Dave - W?LEV
On Sat, Jul 16, 2022 at 8:06 PM Siegfried Jackstien <
siegfried.jackstien@...> wrote:
if in manufacturers smith is shifted in the inductive area ... how can
he claim an swr 1:1 and 50 ohms??
just thinking? (i have not seen the plots)
dg9bfc sigi
Am 16.07.2022 um 18:20 schrieb KENT BRITAIN:
Hi Doug, having done quite a few RFID antennas, that 1 to 1 is rather optimistic.
One thing to consider, do you have any other metal within a foot or so of the antenna? You can easily see a pair of pliers passing a foot or so
from the loop.
Good luck with your project, Kent WA5VJB
On Saturday, July 16, 2022, 11:00:36 AM CDT, Douglas Butler < sherpadoug@...> wrote:
I have a 125 kHz RFID antenna consisting of a coil and series tuning capacitor. The manufacturer supplied plots of the SWR and Z of the antenna
showing a nice 50 Ohm 1:1 SWR at resonance. I have tried to replicate
these plots using my newly purchased NanoVNA and I get radically different
plots showing a load closer to 25 Ohms and a 2:1 SWR. Measuring the L and
C separately gives about the same readings I get with my HP4801 vector
impedance meter at 125kHz, but it is near the upper frequency limit of the
HP4801 so results are shaky. I calibrated the NanoVNA over the same range
as shown in the manufacturer's plots. My Smith plots are centered on the
horizontal axis like I would expect them to be. The manufacturer's plots
are shifted up to the inductive half of the Smith chart. Both show a nice
resonant dip at 125 kHz.
Am I doing something wrong? Is the antenna manufacturer lying?
SherpaDoug WA1UWP
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
|
Re: Antenna VNA comparison with manufacturer
The worst were car stereo amplifier output Watts. Still trying to figure out how they got 300W out of a 12W chip.... 73 -Jim NU0C On Sat, 16 Jul 2022 16:56:28 -0400 "Doug" <jdkearney@...> wrote: Or GMRS radio range!
Doug? -? VA3DKA
On 16/07/2022 16:20, W0LEV wrote:
Remember, marketing has the last word when a product is finally released
for sale. Also, manufacturing variations also play into the whole
picture. I wouldn't be too concerned with anything less than 2:1.
Suppliers can claim anything. Take a look at the gain figures quoted by
the many suppliers of CB antennas. They are outrageous and have no
connection to reality!!!
Dave - W?LEV
On Sat, Jul 16, 2022 at 8:06 PM Siegfried Jackstien <
siegfried.jackstien@...> wrote:
if in manufacturers smith is shifted in the inductive area ... how can
he claim an swr 1:1 and 50 ohms??
just thinking? (i have not seen the plots)
dg9bfc sigi
Am 16.07.2022 um 18:20 schrieb KENT BRITAIN:
Hi Doug, having done quite a few RFID antennas, that 1 to 1 is rather optimistic.
One thing to consider, do you have any other metal within a foot or so of the antenna? You can easily see a pair of pliers passing a foot or so
from the loop.
Good luck with your project, Kent WA5VJB
On Saturday, July 16, 2022, 11:00:36 AM CDT, Douglas Butler < sherpadoug@...> wrote:
I have a 125 kHz RFID antenna consisting of a coil and series tuning capacitor. The manufacturer supplied plots of the SWR and Z of the antenna
showing a nice 50 Ohm 1:1 SWR at resonance. I have tried to replicate
these plots using my newly purchased NanoVNA and I get radically different
plots showing a load closer to 25 Ohms and a 2:1 SWR. Measuring the L and
C separately gives about the same readings I get with my HP4801 vector
impedance meter at 125kHz, but it is near the upper frequency limit of the
HP4801 so results are shaky. I calibrated the NanoVNA over the same range
as shown in the manufacturer's plots. My Smith plots are centered on the
horizontal axis like I would expect them to be. The manufacturer's plots
are shifted up to the inductive half of the Smith chart. Both show a nice
resonant dip at 125 kHz.
Am I doing something wrong? Is the antenna manufacturer lying?
SherpaDoug WA1UWP
|
Re: Antenna VNA comparison with manufacturer
Yes, the VNA is calibrated with short, open, and a 50 Ohm load through the cable. Though at 125kHz a 6" cable should not make much difference.
|
Re: Antenna VNA comparison with manufacturer
Is the NanoVNA calibrated to the end of the coax at the antenna with an open, short, and load?
|
Re: Antenna VNA comparison with manufacturer
Or GMRS radio range!
Doug? -? VA3DKA
toggle quoted message
Show quoted text
On 16/07/2022 16:20, W0LEV wrote: Remember, marketing has the last word when a product is finally released
for sale. Also, manufacturing variations also play into the whole
picture. I wouldn't be too concerned with anything less than 2:1.
Suppliers can claim anything. Take a look at the gain figures quoted by
the many suppliers of CB antennas. They are outrageous and have no
connection to reality!!!
Dave - W?LEV
On Sat, Jul 16, 2022 at 8:06 PM Siegfried Jackstien <
siegfried.jackstien@...> wrote:
if in manufacturers smith is shifted in the inductive area ... how can
he claim an swr 1:1 and 50 ohms??
just thinking? (i have not seen the plots)
dg9bfc sigi
Am 16.07.2022 um 18:20 schrieb KENT BRITAIN:
Hi Doug, having done quite a few RFID antennas, that 1 to 1 is rather optimistic.
One thing to consider, do you have any other metal within a foot or so of the antenna? You can easily see a pair of pliers passing a foot or so
from the loop.
Good luck with your project, Kent WA5VJB
On Saturday, July 16, 2022, 11:00:36 AM CDT, Douglas Butler < sherpadoug@...> wrote:
I have a 125 kHz RFID antenna consisting of a coil and series tuning capacitor. The manufacturer supplied plots of the SWR and Z of the antenna
showing a nice 50 Ohm 1:1 SWR at resonance. I have tried to replicate
these plots using my newly purchased NanoVNA and I get radically different
plots showing a load closer to 25 Ohms and a 2:1 SWR. Measuring the L and
C separately gives about the same readings I get with my HP4801 vector
impedance meter at 125kHz, but it is near the upper frequency limit of the
HP4801 so results are shaky. I calibrated the NanoVNA over the same range
as shown in the manufacturer's plots. My Smith plots are centered on the
horizontal axis like I would expect them to be. The manufacturer's plots
are shifted up to the inductive half of the Smith chart. Both show a nice
resonant dip at 125 kHz.
Am I doing something wrong? Is the antenna manufacturer lying?
SherpaDoug WA1UWP
-- */If you forward this email, please delete the forwarding history which also includes my email address. When sending emails, please BCC so as to hide all addresses. Thanks for helping to prevent Scammers and Spammers from mining addresses and spreading viruses./ Doug Kearney * *Ottawa, ON *
--
This email has been checked for viruses by Avast antivirus software.
|
Re: Antenna VNA comparison with manufacturer
Remember, marketing has the last word when a product is finally released for sale. Also, manufacturing variations also play into the whole picture. I wouldn't be too concerned with anything less than 2:1. Suppliers can claim anything. Take a look at the gain figures quoted by the many suppliers of CB antennas. They are outrageous and have no connection to reality!!! Dave - W?LEV On Sat, Jul 16, 2022 at 8:06 PM Siegfried Jackstien < siegfried.jackstien@...> wrote: if in manufacturers smith is shifted in the inductive area ... how can
he claim an swr 1:1 and 50 ohms??
just thinking? (i have not seen the plots)
dg9bfc sigi
Am 16.07.2022 um 18:20 schrieb KENT BRITAIN:
Hi Doug, having done quite a few RFID antennas, that 1 to 1 is rather optimistic.
One thing to consider, do you have any other metal within a foot or so of the antenna? You can easily see a pair of pliers passing a foot or so
from the loop.
Good luck with your project, Kent WA5VJB
On Saturday, July 16, 2022, 11:00:36 AM CDT, Douglas Butler < sherpadoug@...> wrote:
I have a 125 kHz RFID antenna consisting of a coil and series tuning
capacitor. The manufacturer supplied plots of the SWR and Z of the antenna
showing a nice 50 Ohm 1:1 SWR at resonance. I have tried to replicate
these plots using my newly purchased NanoVNA and I get radically different
plots showing a load closer to 25 Ohms and a 2:1 SWR. Measuring the L and
C separately gives about the same readings I get with my HP4801 vector
impedance meter at 125kHz, but it is near the upper frequency limit of the
HP4801 so results are shaky. I calibrated the NanoVNA over the same range
as shown in the manufacturer's plots. My Smith plots are centered on the
horizontal axis like I would expect them to be. The manufacturer's plots
are shifted up to the inductive half of the Smith chart. Both show a nice
resonant dip at 125 kHz.
Am I doing something wrong? Is the antenna manufacturer lying?
SherpaDoug WA1UWP
-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV
|
Re: Antenna VNA comparison with manufacturer
if in manufacturers smith is shifted in the inductive area ... how can he claim an swr 1:1 and 50 ohms??
just thinking? (i have not seen the plots)
dg9bfc sigi
Am 16.07.2022 um 18:20 schrieb KENT BRITAIN:
toggle quoted message
Show quoted text
Hi Doug, having done quite a few RFID antennas, that 1 to 1 is rather optimistic.
One thing to consider, do you have any other metal within a foot or so of the antenna?? ?You can easily see a pair of pliers passing a foot or so from the loop.
Good luck with your project, Kent WA5VJB
On Saturday, July 16, 2022, 11:00:36 AM CDT, Douglas Butler <sherpadoug@...> wrote:
I have a 125 kHz RFID antenna consisting of a coil and series tuning capacitor.? The manufacturer supplied plots of the SWR and Z of the antenna showing a nice 50 Ohm 1:1 SWR at resonance.? I have tried to replicate these plots using my newly purchased NanoVNA and I get radically different plots showing a load closer to 25 Ohms and a 2:1 SWR.? Measuring the L and C separately gives about the same readings I get with my HP4801 vector impedance meter at 125kHz, but it is near the upper frequency limit of the HP4801 so results are shaky.? I calibrated the NanoVNA over the same range as shown in the manufacturer's plots.? My Smith plots are centered on the horizontal axis like I would expect them to be.? The manufacturer's plots are shifted up to the inductive half of the Smith chart.? Both show a nice resonant dip at 125 kHz.
Am I doing something wrong?? Is the antenna manufacturer lying?
SherpaDoug WA1UWP
|
There aren't many ships (real ships that don't run on underwater wings like the new Independence) that can outrun a torpedo. Even an aircraft-carrier running at 46 knots is NO match for our modern torpedo's.
toggle quoted message
Show quoted text
On 7/16/2022 3:04 PM, Douglas Butler wrote: 12 pound per square foot plate is thicker than 10 pound per square foot. They always go thicker, but the point is they often go different than the designer's plan. If you design a ship to go 24 knots at a certain power level and they build it with thicker plate, it won't make 24 knots. If that means it can't outrun a torpedo then thicker is not always safer.
|
12 pound per square foot plate is thicker than 10 pound per square foot. They always go thicker, but the point is they often go different than the designer's plan. If you design a ship to go 24 knots at a certain power level and they build it with thicker plate, it won't make 24 knots. If that means it can't outrun a torpedo then thicker is not always safer.
|
Oh, never compromise when safety is an issue or anything else for that matter. I'm assuming #12 plate was thinner, not a good choice. My 2 cents worth.
Mike C.
toggle quoted message
Show quoted text
On 7/15/2022 9:49 AM, Douglas Butler wrote: Theory is always incomplete. It is said that the field of thermodynamics learned much more from the operations of steam locomotives than steam locomotives learned from thermodynamics. Often electrical building codes lag advances in electrical technology by decades. In my specialty of ship hull inspection there are always the ship design drawings and the "As Built" drawings. "We ran out of 10# plate so we used 12# plate until we could get more from the foundry."
|
Roger Need
Arie Kleingeld PA3A
Jim Shorney
Douglas Butler
Mike C.