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Re: Measuring low resistance with a NanoVNA
Bob Albert
Steve, can you point me toward that display, and any instructions to retrofit?
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Thank you. Bob K6DDX On Sunday, August 23, 2020, 01:17:23 PM PDT, Stephen Laurence <gaslaurence@...> wrote:
Dear Gary, Agree wholeheartedly. My stable of nano devices consists of an original v2, a v2 with 3.2¡± screen (much easier to use) and a v2 with 4¡± screen and n connectors about to arrive.....and a tinysa. But I do have an original nano, ( currently on loan to a friend). I am intrigued where you placed the diode to light up the battery icon. Could you point me to it please? Out of interest, I got a 3.2¡± screen and it fits and works with the 2.8¡± v2 and although it does not line up with the holes to secure it, it hardly overlaps the vna circuit boards. The small increase in screen size transforms the device. Alas, working from an Ipad, I cannot attach pics. Steve L. G7PSZ |
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Ok, I just read the Whole msg: you've reflowed around the ribbon cable.
Did you do a continuity check from the digitizer input pins on the uP to the solder pads? It's not a software issue. Either the input pins to the uP are bad or you have an open trace (via?) To the display connector. If your ohmmeter has less than 3v at the leads, try measuring the resistance during touch, at the input pins to the uP with the VNA OFF. If I remember correctly, there is a forum post with firmware to test the touchscreen. |
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I had an interesting experience with a touchscreen. It was actually a working nano v2 for which I bought a 3.2¡± screen with the same interface via Ebay.
On plugging it in, all worked except the touch, so I lumbered to the calibrate routine with painful negotiation of the jog and press. Several calibration attempts failed, until I tried touching the bottom right corner when it told me to press the top left, and likewise for the other corner ( then save in Config -at least on the v2). All well, and it works fine with the slightly bigger screen which is easier to read and actually has a virtually identical footprint of the original except a bit of the board which has the pcb tabs for the sd card ( will saw it off), and the holes do not line up for the through standoffs but a tab of glue will do instead. I cannot post before and after pics as I cannot attach on this forum with an Ipad. Steve L. G7PSZ |
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Re: Measuring low resistance with a NanoVNA
Dear Gary,
Agree wholeheartedly. My stable of nano devices consists of an original v2, a v2 with 3.2¡± screen (much easier to use) and a v2 with 4¡± screen and n connectors about to arrive.....and a tinysa. But I do have an original nano, ( currently on loan to a friend). I am intrigued where you placed the diode to light up the battery icon. Could you point me to it please? Out of interest, I got a 3.2¡± screen and it fits and works with the 2.8¡± v2 and although it does not line up with the holes to secure it, it hardly overlaps the vna circuit boards. The small increase in screen size transforms the device. Alas, working from an Ipad, I cannot attach pics. Steve L. G7PSZ |
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Re: Measuring low resistance with a NanoVNA
Regarding this post from Gary from yesterday,
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a few quick explanations that may be obvious to some. Also a bit of what should be considered wild speculation on my part. Some nanovna firmware uses the fundamental all the way to 300mhz, but not all Si5351's are capable of doing this, varies from part to part. For this reason, some firmware uses the fundamental only up to 250mhz. The SiLabs datasheet claims a max of 225mhz. I assume that at 301mhz the nanovna is using 3'rd harmonic out the S11 port in all firmware versions. The Fourier Expansion of a square wave says the 3'rd harmonic has one third the amplitude of the fundamental. The power at 1/3'rd the voltage is down by 20*log10(3) = 9.54 dB, which is what Gary saw with his spectrum analyzer. But had he checked at 100.3 mhz, he likely would have seen the much stronger fundamental. Incidentally, the second port of the Si5351 driving a local oscillator into the bridge is probably using the 5'th harmonic when operating at 301mhz: /g/nanovna-users/topic/33122998#1743 Gary said: Once again though, the drive current leves also alters the source impedance of the si5351ports Has this been measured? I don't think that's necessarily so. SiLabs says the Si5351 has a 50 ohm source impedance on the output. They limit the current, which I assume means this could be modeled as reducing the voltage source that drives the 50 ohm source impedance, all internal to the Si5351. As I stated previously, with programmable Si5351 output current limits at 2,4,6,8 ma, we get a range of 20*log10(8/2) = 12 dB, which could be quite useful. Though this from post 16863 might also be useful: could calibrate with a 3dB pad in the cable for the S11 measurement. The round trip attenuation for the reflection would then be 6dB. However, the local oscillator from the second Si5351 channel into the bridge is still at the same power. I doubt this matters much. Gary wrote: The 900 MHz release version of eddy555¡¯s firmware yields ~ -14 dBm up through maybe 250 MHz or so, then drops off to around -20 dBm at 800 MHz. Hmm, -20 dBm from 250 to 800 mhz? Or drops suddenly to -20 dBm at 800 mhz when moving to the 5'th harmonic? Perhaps edy555 is adjusting the Si5351 output current to be stronger when using harmonics? With -14dBm for the fundamental, edy555 is 7dB weaker than Hugen's firmware. Perhaps he is reducing the current by half and getting (nominally) 6dB weaker?, Without hardware changes, there is not much else he could be doing. Jerry, KE7ER On Sat, Aug 22, 2020 at 07:39 PM, Gary O'Neil wrote:
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1: Try made calibration first
Use leveler select Config->Touch cal Touch top+left screen side Touch bottom+right screen side After check work, use Config->Touch Test If all good - Save config (Confog->Save) In not work (hardware problem): Touch screen use +/- X and Y I/O pins for measure position - check it For get position used ADC For work ADC need correct voltage on on CPU VDDA (pin 9, need ~3.3V) and ground on VSSA (pin 8) |
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Hello - I have some advanced troubleshooting questions in regards to touch screen operations - The touch screen operation hasn't worked since day one on one of my NanoVNA's, likely a clone (no shields installed) was a big hassle in getting a replacement ... and when the vendor said " you can still use it without a touch screen.." well. that did it for me.. I long ago got a refund so its just a troubleshooting challenge on my bench type of thing...spare parts if nothing else...
Here's the problem: When I touch the screen, I can bring up the main start menu on the right side, but that is as far as I get. When I use touchtest, I just get a vertical straight line off on the right side and touchcal outcome never brings up the four sets of numbers. I have loaded it with a few different versions of firmware - no change I have replaced the screen with a new one - no change. I have re-flowed solder around the +/- X and Y I/O pins of the micro - no change There must be some clocks signals and other items needed for touch screen interpolation I should be checking? I'm wondering if a PC trace is missing, damaged, or a via pad not right somewhere, as I'm not finding anymore questionable solder issues under the microscope... just wondering if anyone here has been down similar roads... Other than the touch screen issue, the unit works OK for everything else.. just be nice to get the touch screen working, otherwise it'll be a test bed device on my bench... Thanks! Brian - KI8KY |
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Re: Measuring low resistance with a NanoVNA
Measured on my HP spectrum analyzed. No attempt at precision, and so not calibrated instrumentation results. Relative (between firmware revisions) levels are fine and adequate for the intended purpose. i.e. to determine if a power level change occurred.
N2PK and I are old buds, work colleagues, and IBM retirees. We chat often, and corroborate on projects regularly. He¡¯s a QRO digi DX chaser, and I¡¯m a QRP CW ragchewer, so our QSO¡¯s are a roughly equal mix of email and line. -- 73 Gary, N3GO |
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Re: Measuring low resistance with a NanoVNA
Gary,
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So, exactly how did you measure those power levels? Did you somehow only measure that component of the incident signal that was at the frequency of interest? I totally agree with all sentiments in your post. Any nanovna under $150 that's good enough to evaluate an antenna at 144mhz and less is a very good deal. And they are all cheaper and far more capable that that. Amazing! I've been kibitzing here occasionally, but mostly sit on my hands. The few times I try to actually do anything, my results fall far short of what is already being done. But I am slowly learning. I first took note of the N2PK VNA about 15 years ago, now archived here: There's still an active group for the N2PK, note that Paul is present in the discussion: /g/N2PK-VNA/messages?expanded=1 Here's an HTML version of some of Paul's old notes that are relevant to playing with the nanovna: And, after 15 years, there's still a bunch of things in that introductory document I have yet to fully understand. Jerry, KE7ER On Sun, Aug 23, 2020 at 10:11 AM, Gary O'Neil wrote:
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Re: Measuring low resistance with a NanoVNA
Hi Jerry;
The power levels I posted are measured at the CH0 port. I haven¡¯t been ambitious enough to try digging into the source code to see where the levels were set. Measuring takes less effort. :-) I have been contemplating doing that though; such that I can tweak the device to my own liking. However the developers appear to be coordinating their efforts and doing a fine job without my having to add my two cents. My being patient will present itself as a lesser distraction to them, and allow them to maintain their focus. I¡¯m sure they are critically evaluating their own work, and evidence suggests they will detect and correct the important shortcomings in due course, leaving the user community to follow the story line and appreciate the fruits of their labor. My out of box experience with my original NanoVNA was overwhelmingly satisfactory, and my satisfaction would remain unwavering if I backed off to eddy555¡¯s original 300 MHz firmware today. Since then however; I¡¯ve run it up to 2.7 GHz, added a TDR feature, tapped into Rune¡¯s exceptionally well done NanoVNA-Saver GUI, and during a ¡°What the hell!¡± moment, I even tacked in a 1N4148 diode... just to give that cute little battery icon a tad of personality. I dare say, that all of the technological upgrades that continue to evolve... almost entirely in software, have added value far beyond what any one of us has paid. Even the very worst of known ¡°questionable ¡° clones can hardly be considered anything but an extraordinary value for dollars spent. If/when the ambitious passion of the developers should come to a halt, I will assess the fallout and decide then if ¡°damn good¡± isn¡¯t quite satisfactory enough fo me. After pondering that decision over a cup of coffee or two, I¡¯ll likely express out loud, the revelation I¡¯ve had since spotting the first NanoVNA posted on eBay... ¡°Really!!!¡± I¡¯ll exclaim... ¡°Do I really think I can do that better?¡± From my current vantage point, I suspect my answer will come quickly... ¡°Nah... Not really!¡± -- 73 Gary, N3GO |
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Re: Measuring low resistance with a NanoVNA
Minor correction to my last post:
< 1.5 volts into 50+50=100 ohms, so 1.5/100 = 0.015 ma. 1.5 volts into 50+50=100 ohms, so 1.5/100 = 15 ma.Jerry, KE7ER On Sat, Aug 22, 2020 at 08:55 PM, Jerry Gaffke wrote: Assuming it has a voltage source of 3.0v pk-pk and that we put a 50 ohm |
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Re: NanoVNA-H4 firmware update using Windows virtual machine with macOS
#firmware
#macos
#nanovna-h4
No, it's not the latest firmware. I'd recommend going to the io.group's
files, go to DiLlard's NanoVNA-H Firmware, go to NanoVNA v0.8.2_96kHzIF_3.2kHz_sweep_points.rar, and extract NanoVNA-H4 v0.8.2_96kHzIF_3.2kHz_sweep_point201.dfu. There are files in the files section describing how to use STMicro's software to upgrade. Zack W9SZ <> Virus-free. www.avast.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Sun, Aug 23, 2020 at 12:17 AM Bill Cody via groups.io <wscody= [email protected]> wrote: Newbie NanoVNA-H4 user here with some questions: |
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Re: V2 and V3 roadmap
On 8/23/20 1:21 AM, necessaryevil86@... wrote:
Ahh I see! Makes sense now! But what if you want to analyze the performance of let's say a complex receiver? Don't you need a high bandwith resolution to see the spurs and intermodulation products and stuff?That's done with a spectrum analyzer, not a VNA. |
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NanoVNA-H4 firmware update using Windows virtual machine with macOS
#firmware
#macos
#nanovna-h4
Newbie NanoVNA-H4 user here with some questions:
1) My unit arrived a couple days ago with firmware version 0.5.0. Is this the latest for the H4 model? 2) Has anyone using macOS with Parallels running Windows 10 been able to flash the firmware? I get the unit in DFU mode successfully, the DfuSe Demo windows app successfully sees the VNA, and I successfully load a DFU file into the app, however when I click "Upgrade" the app just sits there with 0% progress. The Device Manager shows all the correct entries in both DFU and normal mode, and NanoVNA-Saver works fine in Windows. Thanks! |
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Re: Measuring low resistance with a NanoVNA
Gary,
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I'm guessing you might have gotten the -7 and -17 dBm figures from the nanovna firmware, and that this jump at 301mhz is due to a switch from the fundamental to using harmonics. So there is still a roughly -7dBm square wave going out when exceeding 300mhz. The Si5351 documention is rather confusing. But to summarize, it claims to have 50 ohm source impedances on the outputs, those 3.3v CMOS outputs have drive levels choices of of 2,4,6,8 ma. Assuming it has a voltage source of 3.0v pk-pk and that we put a 50 ohm capacitively coupled load on the output pin, it's effectively driving 1.5 volts into 50+50=100 ohms, so 1.5/100 = 0.015 ma. The max of 8ma is not sufficient to drive a 50 ohm load, however that 50 ohm source impedance would terminate any reflections coming back from the destination of the clock. Since the Si5351 was meant as a digital clock source, terminating reflections is the primary objective. Here's an old post of mine from exactly a year ago, my simplistic attempt at analyzing the bridge circuit of the nanovna. In the final paragraph I concluded that it would be asking for 8.5 ma from the Si5351. /g/nanovna-users/message/1257 I later had a correction and a few more comments: /g/nanovna-users/message/1265 The rest of that thread might be worth reading if interested in resistive bridge circuits as used in the nanovna. Programming the Si5351 gives us a range from 2ma to 8ma of drive, a factor of 4. Power is proportional to the square of current, so a factor of 16 in power, or 12dB. That's not insignificant, and probably worth having adjustable by the user. Jerry, KE7ER On Sat, Aug 22, 2020 at 07:39 PM, Gary O'Neil wrote:
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Re: Measuring low resistance with a NanoVNA
Roger;
With Hugen¡¯s NanoVNA-H-AA installed, the output power of port 0 measures ~ -7 dBm up through 300 MHz. At 301 MHz it drops to -17 dBm and holds pretty tight to that up through 900 MHz. The 900 MHz release version of eddy555¡¯s firmware yields ~ -14 dBm up through maybe 250 MHz or so, then drops off to around -20 dBm at 800 MHz. I¡¯m certain that the only variability over power is that which results from the the available choices of drive current... I think there are 4, so there¡¯s not much wiggle room to warrant making that a feature on the earlier boards. I haven¡¯t attempted to follow the board upgrades to comment on those with any credibility. Once again though, the drive current leves also alters the source impedance of the si5351ports, and I don¡¯t recall seeing anything that might buffer or isolate impedance changes on any of the ports. BTW... I use the console commands to pull raw data from the device. I didn¡¯t make the observation that the si5351 drive current can be modified within that utility. It doesn¡¯t seem it would be a useful adaptive parameter, but it would merit being a stored system configuration parameter. -- 73 Gary, N3GO |
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Re: Question about measuring an antenna with the nanovna-h
Thanks all for your great answers! There was indeed no ground, so stupid me
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:) One of the antennas was a groundplane antenna, and I would have expected somewhat better behaviour there. It was for 2m and I was still fairly close by. I will try again with the antenna on a small mast about 3m off ground. Am Sa., 22. Aug. 2020 um 07:00 Uhr schrieb alan victor < avictor73@...>: I should add, if the physical size of the vna is comparable to the |
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Re: Measuring low resistance with a NanoVNA
If you don't want to mess with console commands
could calibrate with a 3dB pad in the cable for the S11 measurement. The round trip attenuation for the reflection would then be 6dB. The bridge is still seeing the full incident power. And perhaps bump that pad up to 6dB for the S21 measurement? Paul (N2PK) and I discovered the issue you describe a couple years backVery cool! Creator of the grand-daddy of amateur VNA's. Just google for N2PK. while playing with VIAs that used a strikingly similar archetecture.Also cool, the AQRP VIA. Which I have. Jerry, KE7ER On Sat, Aug 22, 2020 at 04:51 PM, Roger Need wrote: On Sat, Aug 22, 2020 at 03:18 PM, Gary O'Neil wrote:What frequency did you use to measure the power output? The power is increased |
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Re: 7` display module on RA8875 driver + FT5426 capacitive touch in NanoVNA-H4 (now H7) platform
#lcd
Attach screenshot example from SD card
Also for test i use nanoVNA Saver, and it also can grab 401 point and 800x480 image As i see H4 platform allow connect big display, only one slowdown - Smitch chart, render it little slow, better use bitmaps on external flash. |
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