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Re: "Zero calibration" (or "no calibration") question
On 3/4/22 10:26 AM, Kenneth Hendrickson via groups.io wrote:
--- On Friday, March 4, 2022, 10:43:41 AM EST, Miro, N9LR via groups.io <m_kisacanin@...> wrote:Very rarely we get a luxury to connect nano directly to antenna feedGet a set of female SO-238 Short, Open, Load calibration ends, and calibrate at the end of the coax which will attach to the antenna. Or a UHF to SMA adapter (the 1/2" isn't important) and use your existing SMA cal standards. |
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Re: Unit Won't turn on after charging
You can flash the Nano with an ST-Link interface.
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I bought one for $3 from Aliexpress - works great: Also avail on Amazon. I had a similar issue as you're having but only after I had done some soldering on the board - a small ball of solder was stuck across the data lines at the USB connector. Just follow the instructions for the driver here: /g/nanovna-users/topic/34550986 On Friday, March 4, 2022, 01:18:09 p.m. EST, Brady Nelson <tbradynelson@...> wrote:
No luck with a new USB cable, still showing up as "Unknown USB Device (Device Descriptor Request Failed" in device manager. I'm wondering if the firmware can be flashed via serial somehow? I think I may have a USB-serial adapter somewhere. I couldn't figure out how to load the STM driver into Zadig to install the driver, just the generic usb drivers in the dropdown. |
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Re: "Zero calibration" (or "no calibration") question
--- On Friday, March 4, 2022, 10:43:41 AM EST, Miro, N9LR via groups.io <m_kisacanin@...> wrote:
Very rarely we get a luxury to connect nano directly to antenna feedGet a set of female SO-238 Short, Open, Load calibration ends, and calibrate at the end of the coax which will attach to the antenna. 73, Ken N8KH |
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Re: Unit Won't turn on after charging
No luck with a new USB cable, still showing up as "Unknown USB Device (Device Descriptor Request Failed" in device manager.
I'm wondering if the firmware can be flashed via serial somehow? I think I may have a USB-serial adapter somewhere. I couldn't figure out how to load the STM driver into Zadig to install the driver, just the generic usb drivers in the dropdown. |
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Re: "Zero calibration" (or "no calibration") question
On 3/4/22 7:43 AM, Miro, N9LR via groups.io wrote:
In HAM world, one of key uses for nano is antenna tuning, or at least better understanding what my TX is going to see.You can do a SOL calibration at the NanoVNA (that takes out the basic instrument issues) - and then measure your antenna.? As you say, the coax will add a phase shift to the S11, and will show better match (more negative S11 magnitude, lower SWR). cables.png is? two cables measured with the far end open. The other plots are antennas measured using the cable calibration and not. If you use some PC software, you can do a calibration of the coax, once, and save that. Then you can fire up the NanoVNA, tell the software to use the "with coax" calibration, and measure your antenna. |
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"Zero calibration" (or "no calibration") question
In HAM world, one of key uses for nano is antenna tuning, or at least better understanding what my TX is going to see.
Very rarely we get a luxury to connect nano directly to antenna feed point over t-line that can be used in calibration. More often is that I have a random length of coax in place, and can only measure what is at that point. In those cases, it does not matter what I have as a pigtail from nana to antenna system. With full appreciation of what that means (don't know cable losses, cable rotates complex impedance, only SWR reflects what's at the antenna side, ...), and given that a pigtail on nano side is also random selection from immediately available ones but it's length is much shorter then lambda, I need a quick way to calibrate nano with respect to nano's port Now question - what happens when I "reset calibration" on nano - will that in effect be equivalent to calibrating nano directly at the port? If not, what is the quickest way to get calibration that will get me going quickly, without the need for SOL? |
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Re: NanoVNA-H Defective?
First off, Thanks to all that responded.
Further checking on #2 VNA gives the same results; Smith Chart showing a solid 50 Ohm load with No Inputs/Cables connected to S11, on HF / VHF / UHF frequencies, and Calibrated / Not Calibrated. #1 VNA shows a Open for all of the above. So it would appear that it is possibly a dead receiver or at least some internal issue as was suggested so it's going to be sent back. With the first two nanoVNA-H's I've done so many Calibrations that I simply stopped looking at the Smith Chart after completing the calibration. If I would have done that with this #2 VNA (looked at the Smith Chart) I would have see right off that something was indeed wrong internally. Sorry about that... Live & Learn! tnx agn 73's de George WD0AKZ dit - dit |
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Re: New Nano VNA V2 Plus 4 do not draw graph.
Hi Ron,
Thank you for the tip. Someone also suggested same as you said. But there are few other things and until I do not go through them its not going to show the graph properly. I tried changing the scale from 0.25 to 2 with no success. Someone on another group also suggested extra few things. Will do and post the results here. Sohail VE3ITU. |
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Re: New Nano VNA V2 Plus 4 do not draw graph.
Hi Nick,
Thank you for your reply. I already gone through that user guide that you are referring to. As you see I mentioned in my post above but obviously missing some important steps. I got some suggestion from another group. Will post the findings. Sohail VE3ITU. |
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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. |
Donald S Brant Jr
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