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Re: NanoVNA-H Defective?
On 3/2/22 10:21 PM, Colin McDonald wrote:
Odds are good that you either have a problem with the s11 SMA connector on the second #2 NanoVNA, or that your open and short calibration hats are dirty or somewhat defective.A dead receiver on CH0 would show good load, and bad open/short, because in the load case, there's no reflected power. |
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Re: NanoVNA-H Defective?
One thing to try before concluding that a unit is bad would be to reflash the firmware, in case something has gotten corrupted and to be sure you are running current code; this is important in these computerized instruments.
I have had to do this with >$500K Keysight analyzers (they have a convenient recovery partition on their Windows installation), it is not an uncommon occurrence. If it can happen to them..... 73, Don N2VGU |
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Re: NanoVNA-H Defective?
Charlie N2MHS
200 Georges for that Keysight SMA torque wrench ICYAI
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more than the VNA On Thursday, March 3, 2022, 01:21:53 AM EST, Colin McDonald <colinrmcdonald@...> wrote:
Odds are good that you either have a problem with the s11 SMA connector on the second #2 NanoVNA, or that your open and short calibration hats are dirty or somewhat defective. Try at a few different frequencies to be sure. Try VHF and UHF as well as other HF frequencies. If you get the same kind of results there is something wrong. Could be as simple as a bridge solder connection or a defective SMA port on the NanoVNA. The interesting bit is that with the 50Ohm SMA load hat everything looks good on both units. But with the open and short hats #2 is giving strange readings especially for the Z impedance numbers. Do you have a known antenna that you can test with both units for a real world comparison? Regards Colin On 2022-03-02 9:16 p.m., WD0AKZ via groups.io wrote: Yup, I agree... "Something's wrong here, this looks like you're |
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Re: NanoVNA-H Defective?
Odds are good that you either have a problem with the s11 SMA connector on the second #2 NanoVNA, or that your open and short calibration hats are dirty or somewhat defective.
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Try at a few different frequencies to be sure. Try VHF and UHF as well as other HF frequencies. If you get the same kind of results there is something wrong. Could be as simple as a bridge solder connection or a defective SMA port on the NanoVNA. The interesting bit is that with the 50Ohm SMA load hat everything looks good on both units. But with the open and short hats #2 is giving strange readings especially for the Z impedance numbers. Do you have a known antenna that you can test with both units for a real world comparison? Regards Colin On 2022-03-02 9:16 p.m., WD0AKZ via groups.io wrote:
Yup, I agree... "Something's wrong here, this looks like you're measuring your load." |
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Re: NanoVNA-H Defective?
On 3/2/22 8:52 PM, WD0AKZ via groups.io wrote:
I'm sorry, I don't understand "reflection coefficient".The reflection coefficient is the voltage "reflected" back from the unit under test (it's voltage, not power, but it's similar to Ref/Fwd on a directional watt meter) - shorts and opens are "perfect mismatch" so they reflect all the power.? A load absorbs all the power so nothing is reflected (i.e. reflection coefficient is 0) 20 *log10(abs(reflection coefficient) is what's displayed as magnitude of S11.? So short and open, which have a reflection coefficient of -1 and 1, will have S11 of close to 0dB, load should have a reflection coefficient of 0
VNA #1 looks about right. O and S are close to 0dB, and Load is "very small". VNA #2 has something wrong. A short with +85 dB S11 is odd. So the next question is whether it's a computation problem, or is the hardware broken.? You're giving values at some spot frequency - is the value pretty much the same across the band for all 3: S,O, and L?? If you saw -80dB for all three, I'd say "the receiver is broken" - it's not seeing any signal with the short or open. Or, the reference receiver is fouled up.? The measurement is "reflected/reference"? so you could get a tiny number if the reflected is very small, or if the reference is very big. A broken connector (open) would be one cause of no reflected power.? Sometimes, the jack in the middle of a SMA gets bent out of shape and the center pin of the mating plug doesn't make contact. I've also seen things like paint or plastic stuck in the jack. One thing you could do is calibrate your VNA#1, and connect the two CH0 together (with the VNA2 powered off) - the impedance looking into the CH0 should be fairly close to 50 ohms. It's just a resistive bridge.? If it's not, then that's something to investigate.? You could also do a Thru measurement - even without calibration, you should see something around 0 dB (+/- a few dB). The other thing to do is see if there is a signal coming *out* of CH0 when you're making a measurement - if you have a power meter, an RF voltmeter, or a spectrum analyzer, that's something you can check. |
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Re: NanoVNA-H Defective?
Sorry Jim, I forgot to Thank You for your suggestion.? I never thought to verify the OSL on the Smith Chart like I did the first time I went through the Calibration procedure with the first NanoVNA-H I got.
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So my first Nano had a bum USB cable, the Second one works fine, and now this one will have to be returned. Thanks again George On 3/2/2022 11:04 PM, WD0AKZ via groups.io wrote:
Ok, "reflection coefficient" on the Smith Chart?? |
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Re: NanoVNA-H Defective?
Ok, "reflection coefficient" on the Smith Chart??
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Bingo!! VNA #2 on the Smith Chart I see a 50 ohm load on Open, Short and of course Load.? Calibrated or not. It's Broke? George On 3/2/2022 10:52 PM, WD0AKZ via groups.io wrote:
I'm sorry, I don't understand "reflection coefficient". |
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Re: NanoVNA-H Defective?
I'm sorry, I don't understand "reflection coefficient".
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I did now Reset Calibration and looked at the LogMag results if that what you were asking: #1 VNA O= -3db? S- -1db? L= -40db #2 VNA O= -86db? S= 85DB? l= -88db tnx George On 3/2/2022 10:29 PM, Jim Lux wrote:
On 3/2/22 8:16 PM, WD0AKZ via groups.io wrote:Yup, I agree... "Something's wrong here, this looks like you're measuring your load." |
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Re: NanoVNA-H Defective?
On 3/2/22 8:16 PM, WD0AKZ via groups.io wrote:
Yup, I agree... "Something's wrong here, this looks like you're measuring your load." what readings do you get for all three terminations *without calibration*? - the NanoVNA isn't perfect, but you should get close to 1, 0, and -1 for the reflection coefficient. And between two units, you'd expect to see similar values. |
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Re: NanoVNA-H Defective?
Yup, I agree... "Something's wrong here, this looks like you're measuring your load."
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Nope... "Something's wrong here, did you measure your load by accident? " "I'd go back and check the load and short measurements (or the cals) " I repeated this Calibration/test a number of times today, but I just did it again with the same results. Lets say that I am Calibrating/testing correctly, so on the Open/Short tests, regarding the LogMag results, VNA #1 or #2 or Both are correct? tnx George On 3/2/2022 9:54 PM, Jim Lux wrote:
On 3/2/22 5:03 PM, WD0AKZ via groups.io wrote:I have been using antenna tuning devices for a number of years now.? Starting out with VSWR meters, Bird Thru-Line meters, TDR¡¯s, MFJ-259B, and a RigExpert AA-230Zoom which I sold last year.? I came to the conclusion that if I am to remain active in Ham Radio I should still have something for my antenna so I read about the NANOVNA and bought one a couple of weeks ago.? The first one I got had a dead USB Cable so I got another one.? This one appears to work fine so I bought another one as a gift and then decided to compare the two¡Something's wrong here, this looks like you're measuring your load. |
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Re: NanoVNA-H Defective?
So your saying that on the Open test one VNA saying LogMag= 0.01db and the other VNA is LogMag= -86.5db, and on the Short test one VNA having LogMag= 0.00db and the other -80.0db, "VNA readings are acceptable and both are working okay"?
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tnx George On 3/2/2022 9:19 PM, VK2CZ DAVID wrote:
Bob is entirely correct. All VNA's use directional couplers, with the |
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Re: NanoVNA-H Defective?
On 3/2/22 5:03 PM, WD0AKZ via groups.io wrote:
I have been using antenna tuning devices for a number of years now. Starting out with VSWR meters, Bird Thru-Line meters, TDR¡¯s, MFJ-259B, and a RigExpert AA-230Zoom which I sold last year. I came to the conclusion that if I am to remain active in Ham Radio I should still have something for my antenna so I read about the NANOVNA and bought one a couple of weeks ago. The first one I got had a dead USB Cable so I got another one. This one appears to work fine so I bought another one as a gift and then decided to compare the two¡Something's wrong here, this looks like you're measuring your load. Something's wrong here, did you measure your load by accident? I'd go back and check the load and short measurements (or the cals) |
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Re: NanoVNA-H Defective?
On 3/2/22 7:07 PM, montanaaardvark wrote:
On Wed, Mar 2, 2022 at 08:13 PM, WD0AKZ wrote:I agree - the important thing isn't the 20 dB difference. That's down in the noise floor (i.e. you're looking at the difference between a reflection coefficient of 0.0005 and 0.00004).? That is an impressively good load. Or, more probably, you're seeing the noise floor of the calibration.? The mate/demate uncertainty of an SMA is probably greater than that.#1 VNA w/Load Calibration Load: SWR= 1.001 LogMag= -66.3db X= 5mOhm Z= 50.045The way I read this you used the exact same cal standards on both NanoVNAs, right? Standard practice for calibration in the labs I've worked in was to clean both connectors with denatured alcohol and use a calibrated (7 inch*lb) torque wrench for tightening the sets. For every measurement. I'm going to assume you didn't do this and just put them together by hand. |
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Re: NanoVNA-H Defective?
Thanks for the comments Bob...
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Yes, I did use the exact same cals on both NanoVNA's and your are also correct that I did not take lab procedures in doing the tests. The final SWR's in the 50 ohm Load test are in my book close enough, I'm just not clear on why the LogMag numbers in the Open/Short test are so apart.? I'm concerned that what ever data is used to arrive at those numbers may also be used in calculations for other Formats giving unreliable results. I should have noted that both NanoVNA-H's are HW v3.6 and FW v1.1 tnx agn George On 3/2/2022 9:07 PM, montanaaardvark wrote:
On Wed, Mar 2, 2022 at 08:13 PM, WD0AKZ wrote:#1 VNA w/Load Calibration Load: SWR= 1.001 LogMag= -66.3db X= 5mOhm Z= 50.045The way I read this you used the exact same cal standards on both NanoVNAs, right? Standard practice for calibration in the labs I've worked in was to clean both connectors with denatured alcohol and use a calibrated (7 inch*lb) torque wrench for tightening the sets. For every measurement. I'm going to assume you didn't do this and just put them together by hand. |
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Re: NanoVNA-H Defective?
VK2CZ DAVID
Bob is entirely correct. All VNA's use directional couplers, with the
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'uncertainty' around the directivity often confusing measurements. The perfect analog is measuring say a 9v battery with two voltmeters and being confused when one reads 9.000002v and the other 8.999933v when the voltmeter accuracy is only good to +/- 100uV.. Your VNA readings are acceptable and both are working okay.. On Thu, 3 Mar 2022, 14:07 montanaaardvark, <boblombardi@...> wrote:
On Wed, Mar 2, 2022 at 08:13 PM, WD0AKZ wrote:50.045 |
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Re: NanoVNA-H Defective?
On Wed, Mar 2, 2022 at 08:13 PM, WD0AKZ wrote:
The way I read this you used the exact same cal standards on both NanoVNAs, right? Standard practice for calibration in the labs I've worked in was to clean both connectors with denatured alcohol and use a calibrated (7 inch*lb) torque wrench for tightening the sets. For every measurement. I'm going to assume you didn't do this and just put them together by hand. The way I look at this is to turn the return loss values from dB into magnitude by doing 10^(dB/10). I get the values: (-66.3 dB) = 234 *10^-9 (-87.0 dB) = 2.00 *10^-9 I don't have much of a feel for how much to expect out of the H4 since I just bought mine, but while that's a big relative difference (234 to 2), it's between two rather small numbers. How many bits difference is that at the ADC? I have no idea. Look at the VSWRs: 1.001:1 vs. 1.000:1. I can't think of anything I've ever done where a return loss difference like that mattered. Hope that's useful, 73, ___________ Bob - W4ATM -? 35 miles south of the Kennedy Space Center Retired RF Engineer now playing with all the hobbies I never had the time for. |
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NanoVNA-H Defective?
I have been using antenna tuning devices for a number of years now. Starting out with VSWR meters, Bird Thru-Line meters, TDR¡¯s, MFJ-259B, and a RigExpert AA-230Zoom which I sold last year. I came to the conclusion that if I am to remain active in Ham Radio I should still have something for my antenna so I read about the NANOVNA and bought one a couple of weeks ago. The first one I got had a dead USB Cable so I got another one. This one appears to work fine so I bought another one as a gift and then decided to compare the two¡
I calibrated both units using the same set of OEM Calibration OSL SMA Loads connected directly to S11 (no additional cables/connectors) at 14.175mHz. Then I went back and using these same OSL¡¯s at 14.175mHz I compared the two: #1 VNA w/Open Calibration Load: SWR= inf LogMag= 0.01db X= +200kOhm Z= 70300.0 #2 VNA w/Open Calibration Load: SWR= inf LogMag= -86.5db X= +512kOhm Z= 50.003 #1 VNA w/Short Calibration Load: SWR= inf LogMag= 0.00db x= -5.172 Ohm Z= 0.024 #2 VNA w/Short Calibration Load: SWR= inf LogMag= -80.0db X= 5.148mOhm Z= 49.993 #1 VNA w/Load Calibration Load: SWR= 1.001 LogMag= -66.3db X= 5mOhm Z= 50.045 #2 VNA w/Load Calibration Load: SWR= 1.000 LogMag= -87.0db X= 10.0mOhm Z= 49.998 What I¡¯m concerned about is the differences between the LogMag (ReturnLoss) and Z (Impedance) on the Open and Short tests. I would also think that a -21db difference in LogMag between #1 and #2 on the Load test is a bit excessive, or is this just considered ¡°Close enough for Government Work¡± (old saying, somewhat military speak)? I¡¯m assuming that one of these VNA¡¯s is incorrect, am I looking at this wrong? Tnx for any comments George |
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Re: Unit Won't turn on after charging
I had that same thing happen to me... Where windows insisted it had the "best" driver. The problem was it had installed A driver, but actually had the device listed under the wrong category in device manager. In update mode it SHOULD NOT be on a com port it should be as it is shown in the paste below. (as a Universal Serial Bus Controller).You must first remove the device using device manager. If that doesn't work, I eventually used a program called Zadig to manually load the correct driver. But, as was stated by Larry the defective usb cable seemed to be the root issue.
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On Wednesday, March 2, 2022, 04:00:48 PM EST, Larry Rothman <nlroth@...> wrote:
If you're using the original USB cable that came with the Nano - try another one. A number of Nano users have had issues with those original cables. Also, refer to a message thread from a few days ago regarding the device drivers. ? ? On Wednesday, March 2, 2022, 03:42:48 p.m. EST, Brady Nelson <tbradynelson@...> wrote:? Update: Can't get NanoVNA to show up as anything but "Unknown USB Device (Device Descriptor Request Failed" in windows device manager. I have the STM32 drivers installed, and forcing windows to install the drivers fails -- it says it already has the correct drivers installed. Any ideas of something else to try? Maybe the hardware failed somehow, even though I've barely used it. |
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Re: Unit Won't turn on after charging
If you're using the original USB cable that came with the Nano - try another one. A number of Nano users have had issues with those original cables.
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Also, refer to a message thread from a few days ago regarding the device drivers. On Wednesday, March 2, 2022, 03:42:48 p.m. EST, Brady Nelson <tbradynelson@...> wrote:
Update: Can't get NanoVNA to show up as anything but "Unknown USB Device (Device Descriptor Request Failed" in windows device manager. I have the STM32 drivers installed, and forcing windows to install the drivers fails -- it says it already has the correct drivers installed. Any ideas of something else to try? Maybe the hardware failed somehow, even though I've barely used it. |
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Re: Unit Won't turn on after charging
Update: Can't get NanoVNA to show up as anything but "Unknown USB Device (Device Descriptor Request Failed" in windows device manager.
I have the STM32 drivers installed, and forcing windows to install the drivers fails -- it says it already has the correct drivers installed. Any ideas of something else to try? Maybe the hardware failed somehow, even though I've barely used it. |
Donald S Brant Jr
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