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Re: How does VNA get the phase angle of S11
Bob Albert
All this technology for fifty bucks?
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On Wednesday, October 2, 2019, 11:36:26 PM PDT, <erik@...> wrote:
You have the test signal from the SI5351 send to the bridge but also to the "reference" mixer, in the reference mixer it is mixed with the output of the Local Oscillator (LO) which also comes from the SI5351. The unbalance of the bridge goes to the "reflection" mixer where it is mixed with the same LO. The LO is at 5kHz offset from the test signal so the output of both mixers is a IF signal at 5kHz. Both IF's are then read into the controller using the ADC and in a DSP algorithm in the controller the IF's? are going to DSP mixers where they are mixed with two 5kHz signals 90 degrees apart (I/Q mixer) to create a DC signal. The DC signals (I and Q) are the real and imaginary part of the complex downconverted reference and reflection input to the HW mixers. As you do not know the actual angle of amplitude of the test signal the complex test signal is divided by the complex reference signal to eliminate the phase and amplitude uncertainty. The outcome of this division is the unbalance of the bridge scaled relative to the reference signal, both in magnitude and angle. Attached a small pdf that contains the block diagram of a VNA using the same mechanism |
Using the VNWA Testboard Kit
I just got my NanoVNA, and I've never used one before. I spent about two weeks reading whatever I can find to learn more.
To get myself familiar, I purchased the VNWA Testboard kit from SDR-Kits. (www.sdr-kits.net) This is a smal pcb with sockets and parts that allow you to create little circuits a VNA can test. The kit was designed for the VNWA, a instrument in principle not much different from the NanoVNA. () I was hoping to use the same kit with the NanoVNA, unfortunately, I ran into a few issues I can't explain and would like to bring to your attention to see if this can hopefully be resolved, or as a minimum, explained. The kit was connected to the NanaVNA using the supplied cables and calibrated before making any measurements, of course. Measuring resistors works fine with the kit, the values do not have a great accuracy, but are close enough if you stay below 1 KOhms, and even show plausible inductance's of a few nH due to the lead length. Just what I was looking for. Unfortunately, capacitors and inductors do not give plausible (to me) results at all. A 47.28 Ohm resistor is reported to be 46.6 with 7.53uH. (see chart) A 98.85 Ohm resistor is reported as 98.3 with 8.58uH. That's all very good! However, a 68 pF capacitor (with short leads) shows far too much of an inductance on the chart, and is reported to have a resistance of 37 mOhm and 1.59nF. (see chart) A 180 pF capacitor is shown as -89.5u (no unit given, Q?) and 840 pH, no capacitance offered. An inductor of 1uH is reported to have 3.8 KOhm and 370 fF, no inductance offered. (see chart) I've included the screenshots of the PC program, unfortunately, they do not show the reported values. (room for improvement?) Can anybody offer an explanation or better yet, a fix? Thanks, Paul After sending my post off, I noticed that the file names didn't make it. The first file shows the 1uH inductor, the second the 47R resistor and the third file the 68pF capacitor. |
Re: NanoVNA-Saver 0.1.0
Rune,
I am taking a deeper look at your TDR plot. Thanks for implementing this. I think you are plotting all of the samples of the IFFT of the S11 data. If so, I would recommend that you chop off the last half of the plot. With 5 segments (505 total samples) from 50kHz to 900 MHz I am seeing the right side of the plot indicating 55.4 m as the longest distance one could measure. I set the the cable type to RG58/U with a velocity factor of 0.66. I think 55.4 m is too large by a factor of 2. The last half of the bins in the IFFT are time delays that we won't measure in this way with real cables. As it is, you give the impression to someone that they could measure a 55.4 m cable for the settings indicated above which is not correct. Are you applying a frequency domain window function to the data prior to doing the IFFT? If so, it would be useful to let folks know what window you are applying when it comes time for documentation. If not, there are an infinite number of possible windows. I would suggest something fairly easy to implement such as a Hanning window or a Hamming window. For cable length measurement, what you have is great. I am interested in using the TDR to look for impedance deviations along the transmission line which can get easily obscured by time-domain sidelobes if no window is applied. I am using the TDR capability to look for coax damage or breaks in the protective jacket caused by gardening. My coax cables run through a garden area to my antennas which are above the garden. Outright breaks in the coax are fairly easy to find; however, some types of damage are a bit more difficult to observe. The TDR is especially helpful for this application. I do like the separate plotting capability you have implemented for the TDR data which is in the same window as the coax definition. I have noticed that once you put it into the main window as one of the graphs, you cannot ever see the TDR data again as a separate plot unless you restart the program. It seems like it would be a good idea to restore the plot to the TDR window if it is removed from the plots in the main window or just permanently leave it in the separate window that the user can bring up as desired? Another alternative is to only plot the TDR data in the main window. When the TDR plot is a graph in the main window you should show at least the velocity factor you have assumed on the TDR plot and perhaps the cable type the user selected. This makes the plot self-contained when it is saved as an image. I prefer a separate window where I can make the TDR plot as big as my screen; however, that is not in any way essential and probably makes more work for you. Thanks, again, for your great work on this software. I greatly appreciate it. 73, Bryan, WA5VAH |
Re: Another ebay deal?
Dr. David Kirkby from Kirkby Microwave Ltd
On Thu, 3 Oct 2019 at 15:15, Dom Baines M1KTA via Groups.Io <dombaines=
[email protected]> wrote: On Thu, Oct 3, 2019 at 02:44 PM, Dr. David Kirkby from Kirkby Microwave Yes. Note that there¡¯s a basic board and are more advanced one. Both are under ?20. I think that they are designed to be *educational*. I am not saying that the Chinese board is totally useless, but for a PCB with connectors that have quite a limited lifetime, and a small number of cheap components, it seems quite expensive to me. Dave --Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom |
Re: NEW - Two-Trace Antenna Analyser (AA) Oct-3-19 firmware versions now available
Really just a larger font with only 2 traces available - do not install yet - they are buggy.
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On Thursday, October 3, 2019, 9:59:27 a.m. GMT-4, mike watts via Groups.Io <wy6k@...> wrote:
Larry,? Does the AA version do anything that the other version does not?? Or is it just the readability? Mike WY6K "... somewhere in the distance, there's a tower and a light, broadcastin' the resistance, through the rain and through the night..." ? ? On Thursday, October 3, 2019, 8:16:46 AM CDT, Larry Rothman <nlroth@...> wrote: Folks, Hugen has built several up-to-date (as of Oct 3, 2019) versions of his Antenna Analyser (AA) firmware for the NanoVNA. These have the thicker fonts that ware easier to read. The entire drive download is 20MB and contains a lot of older files, so you may want to only D/L what you need. On the Google drive here: ? ? ? ? ? bin, hex & dfu files: NanoVNA-H__900_ch_20191003 NanoVNA-H__900_aa_20191003 NanoVNA-H__800_ch_20191003 NanoVNA-H__800_aa_20191003 |
Re: NEW - Two-Trace Antenna Analyser (AA) Oct-3-19 firmware versions now available
DO NOT INSTALL the AA versions of hugen's Oct-3-2019 firmware
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- they are buggy and will lock-up your device right after calibrating the touchscreen! Please wait until hugen fixes them. The CH versions work as far as I have tested. On Thursday, October 3, 2019, 9:17:55 a.m. GMT-4, Larry Rothman <nlroth@...> wrote:
[Edited Message Follows] [Reason: fixed typo] Folks, Hugen has built several up-to-date (as of Oct 3, 2019) versions of his Antenna Analyser (AA) firmware for the NanoVNA. These have the thicker fonts that are easier to read. The entire drive download is 20MB and contains a lot of older files, so you may want to only D/L what you need. On the Google drive here: ? ? ? ? ? bin, hex & dfu files: NanoVNA-H__900_ch_20191003 NanoVNA-H__900_aa_20191003 NanoVNA-H__800_ch_20191003 NanoVNA-H__800_aa_20191003 |
Re: Another ebay deal?
On Thu, Oct 3, 2019 at 02:44 PM, Dr. David Kirkby from Kirkby Microwave Ltd wrote:
You mean this one? The suggestion of the ebay board stimulated discussion which is a good thing as I suspect some will have a need to see could this test 'whatever' and if it does what does the output look like? I would have thought either might be a step up from a veroboard or a bit of FR4 (or better) with an SMA on either end and some test circuit or mount in between. I am sure many of us have created such PCB with bnc/sma etc at either end you put/mount/wire some test rig or item in between. Might be a guess but expect lpf/bpf, xta filters, RC/LC networks and a number of devices have been tested in this manner before (not with the nanovna of course) If you have alternative suggestions for ready made cheap test boards I am sure many would love to hear about them? 72 Dom M1KTA |
Re: NanoVNA-Saver 0.1.0
Hi Mike,
way to up the ante! I'm getting nervous now! ;-) I'll see how much of it I can figure out for the next release. -- Rune / 5Q5R On Thu, 3 Oct 2019 at 15:45, mike watts via Groups.Io <wy6k= [email protected]> wrote: Yes, all of those filter measurements would be useful for things I do. |
Re: NEW - Two-Trace Antenna Analyser (AA) Oct-3-19 firmware versions now available
Larry,?
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Does the AA version do anything that the other version does not?? Or is it just the readability? Mike WY6K "... somewhere in the distance, there's a tower and a light, broadcastin' the resistance, through the rain and through the night..." On Thursday, October 3, 2019, 8:16:46 AM CDT, Larry Rothman <nlroth@...> wrote:
Folks, Hugen has built several up-to-date (as of Oct 3, 2019) versions of his Antenna Analyser (AA) firmware for the NanoVNA. These have the thicker fonts that ware easier to read. The entire drive download is 20MB and contains a lot of older files, so you may want to only D/L what you need. On the Google drive here: ? ? ? ? ? bin, hex & dfu files: NanoVNA-H__900_ch_20191003 NanoVNA-H__900_aa_20191003 NanoVNA-H__800_ch_20191003 NanoVNA-H__800_aa_20191003 |
Re: NanoVNA-Saver 0.1.0
Yes, all of those filter measurements would be useful for things I do.? Those functions would elevate you from "hero" to "demi-god" in my world.? :-)
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Mike WY6K "... somewhere in the distance, there's a tower and a light, broadcastin' the resistance, through the rain and through the night..." On Thursday, October 3, 2019, 4:20:50 AM CDT, Rune Broberg <mihtjel@...> wrote:
Hi Norbert, the application can run calibrations at far more than 401 points - I have certainly done 5050 points at one point. ;-) But it does this in the application, and not on the device, due to the hardware limitations. I agree that a function to find cut-off frequencies for filters etc. would be interesting, and I've put it on the list of features I would like to implement for the next version, ie. for next week. I don't make any promises though :-) What measurements would be relevant to provide? Cut-off frequency, span for band-pass, dB/octave and dB/decade fall-off, pass-band ripple? -- Rune / 5Q5R On Thu, 3 Oct 2019 at 11:12, <norbert.kohns@...> wrote: Hi Rune, |
Re: Another ebay deal?
Dr. David Kirkby from Kirkby Microwave Ltd
On Thu, 3 Oct 2019 at 09:53, Gerry Kavanagh via Groups.Io <gerrykav=
[email protected]> wrote: Nice idea. I wonder how long those little u.fl connectors will last though. Hirose, the designer of the U.FL connector, says *20 matings. * IMHO, it would be cheaper and better to just get some chassis mount SMA connectors and assemble something oneself. eBay item 183574973423 has 5 SMA connectors at $2.80 delivered to the UK. * Opens can be made free. * Shorts can be made for the cost of a bit of solder.??? * Other devices can be made very cheaply. Working out the S-parameters If you look at the cost of that board, it is *much* more expensive than far more sophisticated PCBs available from China. To me at least, it seems a relatively large amount of money for something that has very little substance to it. SDR-KITS sell a test board that seems to offer much more room for experimentation at a better price. Dave -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom |
NEW - Two-Trace Antenna Analyser (AA) Oct-3-19 firmware versions now available
Folks,
Hugen has built several up-to-date (as of Oct 3, 2019) versions of his Antenna Analyser (AA) firmware for the NanoVNA. These have the thicker fonts that are easier to read. The entire drive download is 20MB and contains a lot of older files, so you may want to only D/L what you need. On the Google drive here: bin, hex & dfu files: NanoVNA-H__900_ch_20191003 NanoVNA-H__900_aa_20191003 NanoVNA-H__800_ch_20191003 NanoVNA-H__800_aa_20191003 |
Re: Firmware file size now smaller?
Great answer thanks. I think though this time I'll just get the 800 file because I do not need to analyze at 900 MHz (not even 800 really).
As everyone already knows, this little unit is amazing for the price. I've already convinced several friends in the area to buy one. |
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