Re: Cheap calibration loads
#parts
68 ohms (resistance) will give you a VSWR of 1.36, so it's very nearly in
spec, according to the soec sheet you linked.
-. Aldo
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On Sat, Jan 25, 2020, 4:09 PM <cosbug@...> wrote:
Hello All,
Could someone advise if these SMA terminators are good ?
I've done a resistance check at DC using multimeter and it's shown 68 Ohms
(too high by me, should be lower).
Secondly, I've attached to VNA (properly calibrated with other known good
50 Ohm SMA) and the result is:
1. At frequencies lower than 100Mhz SWR is 1.3.
2. In 1Ghz range has significant capacitance impedance.
The item is rated DC-18Ghz TRM-2444-M0-SMA-02 (specs https:
www.mouser.co.uk/datasheet/2/643/pi-CCS-MW-TRM-2444-M0-SMA-02-1312942.pdf)
Am I doing something wrong or terminators are defective ?
Pictures attached.
Regards,
Constantin
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Re: Cheap calibration loads
#parts
On Sat, Jan 25, 2020 at 01:08 PM, <cosbug@...> wrote:
Could someone advise if these SMA terminators are good ?
I've done a resistance check at DC using multimeter and it's shown 68 Ohms (too high by me, should be lower).
Secondly, I've attached to VNA (properly calibrated with other known good 50 Ohm SMA) and the result is:
1. At frequencies lower than 100Mhz SWR is 1.3.
2. In 1Ghz range has significant capacitance impedance.
The item is rated DC-18Ghz TRM-2444-M0-SMA-02 (specs https: www.mouser.co.uk/datasheet/2/643/pi-CCS-MW-TRM-2444-M0-SMA-02-1312942.pdf)
Am I doing something wrong or terminators are defective ?
===========================================================
Constantin from your attached photos you have a reason to be suspect. The low cost terminator that came with my NanoVNA-H4 has a return loss of over 40 dB up to 1 GHz, and the Midwest Microwave terminator in your photo is showing a return loss of 20 dB at some frequencies. That's pretty poor and definitely outside the specifications of the device.
I have come across similar Midwest Microwave terminators at swap fests and I cherry pick them using the NanoVNA I always carry with me. The sellers aren't very thrilled because they are left with known subpar terminations on their table while I walk away with the in spec devices.
- Herb
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Re: nanovna-users]NanoVNA-H4 2Port calibrationof
On Sat, Jan 25, 2020 at 12:37 PM, Jos Stevens wrote:
yes I did use the calibration wizard and I have done it so often that I can do it blindfolded..
The only thing different is that For the H4 I used portsavers and used one of the cables that were in the box of the -H4, the firmware is still from the first of Januari 2020, I did not upgrade yet because I learned that there are problems with the new firmware.
Anyhow you say that you have no problems, I'm using NanoVNA-Saver 0.2.2.1, the latest version as far as I know. I hardly can believe that the problem is in the hardware, because the hardware stand alone shows "Ch1 Logmag 10 dB/-1.42 dB @ 50 kHz" , -0.07 dB @ 810Mhz and -1.55 dB @ 1500 MHz after a 101 point calibration. A minute ago I ran the calibration again on NanoVNA-Saver and attached the pictures before and after pressing "Apply".
================================================================================================
Jos,
I re-did my calibration trying to match as closely as possible the settings you used except I had already set things up before I saw your follow-up regarding the number of segments you used. I used 4 segments (404 pts) but that shouldn't matter.
The main difference I see is that I had already cal'd my NanoVNA-H from 50k-1GHz and just changed my stop frequency to 1.5GHz to match yours. Even so my "before" S21 plot (red trace in attachment) looks better than your "before" s21 plot. If you did a 50k-1.5GHz calibration on your NanoVNA-H4 and stored it in Save 0, your before s21 plot should look a lot better than it does. The black trace in the attached photo is my s21 thru measurement after calibration.
I believe if you go into NanoVNA-saver with a good 50k-1.5GHz SOLT calibration, saved to SAVE 0 on your NanoVNA-H4, that your issue should resolve itself.
- Herb
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Re: Cheap calibration loads
#parts
Hmmm...looks like a Nano-Cantenna ;-)
On Sat, 25 Jan 2020 at 3:34 PM, hwalker<herbwalker2476@...> wrote: Ever wonder why some 50 ohm loads are reasonably priced, look great at dc, but quickly veer off 50 ohms at higher frequencies?? Take a look at the attached photo, courtesy of one of the Russian NanoVNA boards, and wonder no more.? The ground lead even looks it is compression contact instead of soldered.
- Herb
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Re: Cheap calibration loads
#parts
Hello All,
Could someone advise if these SMA terminators are good ?
I've done a resistance check at DC using multimeter and it's shown 68 Ohms (too high by me, should be lower).
Secondly, I've attached to VNA (properly calibrated with other known good 50 Ohm SMA) and the result is:
1. At frequencies lower than 100Mhz SWR is 1.3.
2. In 1Ghz range has significant capacitance impedance.
The item is rated DC-18Ghz TRM-2444-M0-SMA-02 (specs https: www.mouser.co.uk/datasheet/2/643/pi-CCS-MW-TRM-2444-M0-SMA-02-1312942.pdf)
Am I doing something wrong or terminators are defective ?
Pictures attached.
Regards,
Constantin
|
Re: nanovna-users]NanoVNA-H4 2Port calibrationof
I forgot to mention That I used 10 Segments in NanoVNA-Saver
Jos
Op 25-1-2020 om 21:37 schreef Jos Stevens:
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Hi Oristo and Herb,
Thinks for the pictures Oristo, i think they are from the 2.8" NanoVNA-H, my 2.8 -H version works well, this problem is? with my VNA new version H4.
Herb,? yes I did use the calibration wizard and I have done it so often that I can do it blindfolded..
The only thing different is that For the H4 I used portsavers and used one of the cables that were in the box of the -H4, the firmware is still from the first of Januari 2020, I did not upgrade yet because I learned that there are problems with the new firmware.
Anyhow you say that you have no problems,? I'm using NanoVNA-Saver 0.2.2.1, the latest version as far as I know. I hardly can believe that the problem is in the hardware, because the hardware stand alone shows "Ch1 Logmag 10 dB/-1.42 dB @ 50 kHz" , -0.07 dB @ 810Mhz and -1.55 dB @ 1500 MHz after a 101 point calibration. A minute ago I ran the calibration again on NanoVNA-Saver and attached the pictures before and after pressing "Apply".
What can I do more ?
Jos
Op 25-1-2020 om 19:04 schreef hwalker:
On Sat, Jan 25, 2020 at 09:19 AM, Jos Stevens wrote:
" I'm testing my new NanoVna-H4 iusing NanoVNA-Saver and have? a problem doing the 2 port calibration"
=======================================================================================
Jos,
??? I just performed a full 2-port calibration of my NanoVNA-H4 using NanoVNA-Saver and did not experience any problems.? Did you use the calibration wizard?? It should direct you through a full 1-port calibration and then ask if you want to continue with a 2-port calibration.? If you follow the directions and still have problems with s21 results, then you may want to verify that the cables and barrel you are using for through calibration are not defective (it occasionally happens).
- Herb
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Re: nanovna-users]NanoVNA-H4 2Port calibrationof
Hi Oristo and Herb,
Thinks for the pictures Oristo, i think they are from the 2.8" NanoVNA-H, my 2.8 -H version works well, this problem is? with my VNA new version H4.
Herb,? yes I did use the calibration wizard and I have done it so often that I can do it blindfolded..
The only thing different is that For the H4 I used portsavers and used one of the cables that were in the box of the -H4, the firmware is still from the first of Januari 2020, I did not upgrade yet because I learned that there are problems with the new firmware.
Anyhow you say that you have no problems,? I'm using NanoVNA-Saver 0.2.2.1, the latest version as far as I know. I hardly can believe that the problem is in the hardware, because the hardware stand alone shows "Ch1 Logmag 10 dB/-1.42 dB @ 50 kHz" , -0.07 dB @ 810Mhz and -1.55 dB @ 1500 MHz after a 101 point calibration. A minute ago I ran the calibration again on NanoVNA-Saver and attached the pictures before and after pressing "Apply".
What can I do more ?
Jos
Op 25-1-2020 om 19:04 schreef hwalker:
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On Sat, Jan 25, 2020 at 09:19 AM, Jos Stevens wrote:
" I'm testing my new NanoVna-H4 iusing NanoVNA-Saver and have a problem doing the 2 port calibration"
=======================================================================================
Jos,
I just performed a full 2-port calibration of my NanoVNA-H4 using NanoVNA-Saver and did not experience any problems. Did you use the calibration wizard? It should direct you through a full 1-port calibration and then ask if you want to continue with a 2-port calibration. If you follow the directions and still have problems with s21 results, then you may want to verify that the cables and barrel you are using for through calibration are not defective (it occasionally happens).
- Herb
|
Cheap calibration loads
#parts
Ever wonder why some 50 ohm loads are reasonably priced, look great at dc, but quickly veer off 50 ohms at higher frequencies? Take a look at the attached photo, courtesy of one of the Russian NanoVNA boards, and wonder no more. The ground lead even looks it is compression contact instead of soldered.
- Herb
|
Another suggestion to reduce novice frustration is to advise them to download the ST files using a PC that has their email client installed, in order to pass ST¡¯s identity verification scheme.
Regards,
Bruce W4CG
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On Jan 24, 2020, at 13:53, Oristo <ormpoa@...> wrote:
Hi Gyula -
this info from ST site:
STSW-LINK009 Active I suppose that is
.. which appears to be for ST-Link, NOT nanoVNAs..
Installing drivers from there may provoke a problem that we trying to avoid,
namely folks trying to use DfuSe Demo, but having a driver for ST-Link installed.
I suppose that folks should be directed to
for DFU drivers, instead of
Will including all three of those in /g/nanovna-users/wiki/drivers
help or confuse?
FWIW, to test documentation, I am experimenting on a relatively virgin Windows 10 PC:
* Device Manager reports STM32 BOOTLOADER when >>NO<< matching driver is installed.
* my Python scripts (e.g. ) communicate successfully with nanoVNA by COM3 using Microsoft's USB Serial Device driver.
Downloading and installing DfuSe from
(after receiving and responding to confirmation email)
automagically installed the "STM Device in DFU Mode" driver
.. which is located at C:\Program Files (x86)\STMicroelectronics\Software\DfuSe v3.0.6\Bin\Driver\
<STM_DFUdriver.png>
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Re: Testing Cookbook Using a VNA
Thanks for the link; that is a useful resource. - Ed
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Re: nanovna-users]NanoVNA-H4 2Port calibration
On Sat, Jan 25, 2020 at 09:19 AM, Jos Stevens wrote:
" I'm testing my new NanoVna-H4 iusing NanoVNA-Saver and have a problem doing the 2 port calibration"
=======================================================================================
Jos,
I just performed a full 2-port calibration of my NanoVNA-H4 using NanoVNA-Saver and did not experience any problems. Did you use the calibration wizard? It should direct you through a full 1-port calibration and then ask if you want to continue with a 2-port calibration. If you follow the directions and still have problems with s21 results, then you may want to verify that the cables and barrel you are using for through calibration are not defective (it occasionally happens).
- Herb
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Re: nanovna-users]NanoVNA-H4 2Port calibration
Here are polar plots for CH1 connected to CH0
corrected vs uncorrected
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Re: nanovna-users]NanoVNA-H4 2Port calibration
Are there others that have seen this ? Here are screen captures from my "worse clone" for uncorrected vs corrected
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nanovna-users]NanoVNA-H4 2Port calibration
I'm testing my new NanoVna-H4 iusing NanoVNA-Saver and have? a problem doing the 2 port calibration .
When I have done the last item of the calibration procedure (through) I see a nice sinewave-like trace around zero in the S21 Chart. This obviously is the uncalbrated S21.
When I press "apply"? this trace should be? updated? closer to 0 by the correction, but instead of that it drops down 35dB with a lot of noise above 900 MHz . The other charts are updated correctly as far as I can see.
The same thing happens ofcourse when the calibration has been saved and (re)used.
Are there others that have seen this ?
Jos
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Re: Testing Cookbook Using a VNA
Interesting, the link goes to a channel that says there are no videos!
3 part video tutorial
Link added in /g/nanovna-users/wiki/User-Guides
I just reconfirmed it working using a different (Safari) browser not logged into YouTube
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Re: Full reflection runs over the perimeter of the smith chart
Does anyone else see the same symptom? No, but I do not have semi rigid coax.. First measurement using 35cm RG316 shows loss from 250-400MHz. Second measurement using longer LMR-400 shows loss from 41.67-66.67MHz, approximately matching the frequency/length ratio. I did not bother recalibrating, since I would expect that to only impact accuracy, not relative frequency-dependent losses..
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Re: Full reflection runs over the perimeter of the smith chart
On Fri, Jan 24, 2020 at 09:26 AM, Norbert Kohns wrote:
I am wondering, that at full reflection the response moves over the perimeter
of the smith chart.
Hello Norbert, I think it has to do with calibration. After calibration direct at the nanoVNA CH0 SMA female plug, a 1 m coax cable connected to the reference plane with open at its other end, should give *perfect circles spiraling inwards* in the smith chart, see below. In the program nanoVNA-saver *no extra calibration* was used. Compared with the measured 101 points of the nanoVNA, the curve in the nanoVNA-saver program looks much smoother with 505 points. See the picture on the right and below. For more details have a look to my web page: 73, Rudi DL5FA
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Re: Testing Cookbook Using a VNA
There exist a very good kindle e.book about the Nano Vna :
73 de Klaus, DL7AIR
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On Sat, Jan 25, 2020 at 04:54 AM, <sidebores@...> wrote:
Can someone tell me please do you have to calibrate everytime you change the start and stop frequency limits. Or is the cal good if its within the original cal eg 50Mhz to 400Mhz to 70Mhz to 300Mhz.
==================================================================
The best way to judge for yourself whether re-calibrating is necessary is to do the math.
The NanoVNA only has 101 measurement points available so if your original calibration range was 50 kHz - 900 MHz, then your calibration points are spaced every (900e6-50e3)/101 = ~8.9 MHz. If you were to change the measurement range to 50 kHz - 30 MHz then there are only 3 calibration points within that range. and almost all of your measurement data will be interpolated from those three measurement points. If your device under test (DUT) has a broad response then you may not notice any error. If the DUT has a lot of narrowband responses then the error can be significant.
In the test case you presented where the original calibration was 50Mhz - 400Mhz, then the calibration points are spaced every (400e6-50-6)/101 = ~3.5 MHz. If you change the range to 70Mhz - 300Mhz, then you have about 67 calibration points in that range which may be sufficient enough to not warrant re-calibration.
If you find yourself using the same measurement ranges on a regular basis, then calibrate and save those ranges to any of the other 4 memory locations and then you can recall them without re-doing the calibration at any time.
- Herb
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Aldo Cugnini
Oristo
