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Re: Some basic load measurements
There appears to be TWO different loads provided with the NanoVNA instrument. I reported this in an earlier message. The 50 ohm termination with the white gecko unit was pretty poor and demonstrated a 18 dB return loss at 900 MHz. That has since been degraded to 16 dB after about 3 weeks of using it. When I first measured it NEW it showed a series inductance of approximately 500 pH.
The termination kit 50 ohm with the black VNA unit is considerable better. I measured about 44 dB RTL across the 50 kHz to 900 MHz range. I would consider that quite good. Again as a point of reference, the APC -7 precision connectors provided by Keysight are 53 dB return loss DC-to- 5 GHz. These are the so called sexless connector. Very nice. I think you should be pleased with a 40 dB + RTL. Far more important, after you find such a wonderful and precise load, take care of it. As soon as you use it and if you allow the center pin to rotate just ONCE, your return loss will be shot! A bit of gold will be scraped off the center pin to rest upon the dielectric. Do that a few times and watch the trail of parasitic L/C begin to build. The return loss is out the window. Regards, Alan ________________________________ From: [email protected] <[email protected]> on behalf of Peter Gottlieb <hpnpilot@...> Sent: Thursday, August 8, 2019 1:52 AM To: [email protected] <[email protected]> Subject: Re: [nanovna-users] Some basic load measurements I made some further measurements using the 8753 setup. I did the OSL cal on one port and looked at both the Smith chart as well as S11. I didn't bother with the cheap BNC load. I used averaging (16) to get more stable measurements. The Smith chart was of little use as each load showed up as a tiny one pixel dot almost exactly in the middle. However, it does display reactance values. All the values here are from the 8753. Load R Z contrib ohms value S11 @ 900 MHz OSL 50.000 0.0000 0.0000 H -76 dB (noisy) Nano 49.184 0.4255 76.942 pH -40.673 dB Narda 50.438 -33.203 m 5.3205 nF -47.356 dB Tiny 49.389 0.5977 105.58 pH -40.678 dB Note the resistance values on the 8753 differ from the DC resistance somewhat, even normalizing to the OSL value. You can clearly see the OSL becomes the definition of 50 ohms and the S11 is at the analyzer noise floor. tuckvk3cca pointed out how the 1.02 SWR corresponded to a 40 dB return loss and he is spot on. The Narda shows the best return loss at 900 MHz of better than 47 dB. What would be considered a high quality load? The one that comes with the NanoVNA is not terrible considering the other tiny one I have, which has a NSN number on it, is very similar. Not that having a NSN number infers anything spec particular, but at least it will have a minimum set of specs so somebody thought about it. I note that the very small SMA terminations are slightly capacitive while the 1.5" long Narda termination (it probably has some power rating) is slightly inductive. These variations are too small to see on the Smith chart at regular scale. Peter On 8/6/2019 10:43 PM, Peter Gottlieb via Groups.Io wrote: Resending from website as it didn't seem to go through as a message. Also my pasted table from Excel lost formatting so I tried to fix it to be more readable. |
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Re: Measurement challenge
Wow, I have not seen those since I was a child, say age 13!
Yes, I suppose they would work fine! What I had in mind and what I am currently having pretty good success with is a Pomoma grabber cable to a BNC connector. I am calibrating in a BNC environment. I adapt from SMA to BNC. Built a BNC short, open and have a commercial hp 50 ohm termination. Not pretty, but 50 kHz to 30 MHz so far reasonably effective. I will try to photo the test set and results. [cid:42067b24-ec64-4b89-9b13-5fef48015439] ________________________________ From: [email protected] <[email protected]> on behalf of Larry Rothman <ac293@...> Sent: Thursday, August 8, 2019 1:27 AM To: [email protected] <[email protected]> Subject: Re: [nanovna-users] Measurement challenge Alan, Alligator clips are so yesterday... I've got some great Fahnestock clips for you! ;-) |
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Test drivers wanted.
Anybody wish to volunteer to perform the task of loading and comparing firmware¡¯s and/or versions/release levels?
It would be nice to avoid the judgmental pitting of one against any all others; so I think what is needed and most welcomed by most of us at this stage of our collective level of knowledge and understanding; is a general, but informed, overview with useful comments of how each behaves... not a detailed blow by blow walk through of every operation. The intent is to establish a sense of stability (bugginess), ergonomic improvements, feature adds/changes, and general user observations to guide users with meaningful and relevant information when assessing if and when a change or upgrade might better serve their own needs. Not doing so relegates the task to all of us flailing through the exercise on our own. The redundancy of this approach is likely to escalate into multiple divergent and opinionated threads causing the task of making an informed decision unachievable. That said... If you feel you can take this on before we become overwhelmed with firmwares coming at us from every direction, you will certainly be of high value to the group; both by those that are new to VNA¡¯s, and those who are seasoned, experienced, and most able to contribute in a focused manner to educate and advance our understanding and utility of the NanoVNA in particular, and VNA¡¯s in general. -- 73 Gary, N3GO |
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Re: Some basic load measurements
I made some further measurements using the 8753 setup.
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I did the OSL cal on one port and looked at both the Smith chart as well as S11. I didn't bother with the cheap BNC load.? I used averaging (16) to get more stable measurements. The Smith chart was of little use as each load showed up as a tiny one pixel dot almost exactly in the middle.? However, it does display reactance values. All the values here are from the 8753. Load??????? R??????????????? Z contrib ohms???? value S11 @ 900 MHz OSL???????? 50.000????????? 0.0000???????????????? 0.0000 H -76 dB (noisy) Nano????? 49.184????????? 0.4255???????????????? 76.942 pH -40.673 dB Narda???? 50.438 ? ? ?? -33.203 m? ?????????? 5.3205 nF -47.356 dB Tiny??????? 49.389 ???????? 0.5977 ???????????????? 105.58 pH -40.678 dB Note the resistance values on the 8753 differ from the DC resistance somewhat, even normalizing to the OSL value.? You can clearly see the OSL becomes the definition of 50 ohms and the S11 is at the analyzer noise floor. tuckvk3cca pointed out how the 1.02 SWR corresponded to a 40 dB return loss and he is spot on.? The Narda shows the best return loss at 900 MHz of better than 47 dB. What would be considered a high quality load?? The one that comes with the NanoVNA is not terrible considering the other tiny one I have, which has a NSN number on it, is very similar.? Not that having a NSN number infers anything spec particular, but at least it will have a minimum set of specs so somebody thought about it. I note that the very small SMA terminations are slightly capacitive while the 1.5" long Narda termination (it probably has some power rating) is slightly inductive.? These variations are too small to see on the Smith chart at regular scale. Peter On 8/6/2019 10:43 PM, Peter Gottlieb via Groups.Io wrote:
Resending from website as it didn't seem to go through as a message. Also my pasted table from Excel lost formatting so I tried to fix it to be more readable. |
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Re: Problem with shorts and load in cal kits
Dr. David Kirkby from Kirkby Microwave Ltd
On Thu, 8 Aug 2019 at 02:08, Gary O'Neil <n3go@...> wrote:
Good observation Dave; Yes, I had thought about a video on that. I have a video camera, but since I am a Unix person I had problems getting the data off of the card reader. I tried a virtual machine, but that didn¡¯t work. I only have the one video on YouTube, which I took with my mobile whilst doing the task and fighting hayfever. Connector savers will not impact the calibration quality, whereas any attempt to improve the mechanical properties of the short will cause problems Dave -- Dr. David Kirkby, |
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Re: Problem with shorts and load in cal kits
Good observation Dave;
Alan¡¯s suggestion to use SMA Male-Female adapters to protect the connectors on the NanoVNA would be prudent also. Both also give us something to scrounge for and haggle a bargain at our next hamfest. :-) The care and feeding of RF connectors in general might be a useful topic for your next YouTube video. As you know improper use of RF connectors can be equally destructive as using connectors of marginal quality. -- 73 Gary, N3GO |
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Re: Annotated nanoVNA menu diagram
Looks real good. I think it needs a button to get you back to the main page. I guess the browser back is the only way to do that
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Thanks Frank On 8/7/2019 8:09 PM, Stuart Landau via Groups.Io wrote:
Terrific addition to our knowledge of the NanoVNA. |
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Re: Measurement challenge
Or turn that around: how sloppy can you be with HF construction techniques and still have reasonable results?
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Peter On Aug 7, 2019, at 8:29 PM, alan victor <avictor73@...> wrote: |
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Re: Measurement challenge
Yes, that is an excellent test. If you make use of a somewhat narrow sweep so with 101 data points you can obtain the required resolution, you can find the +/- 45 degree phase shift points for S21. This will pull out the -3 dB bandwidth. I'll have to see if I can conduct such a test.
However, for now I have been conducting a much simpler measurement challenge. That is after CAL, obtaining a reasonable accurate measurement of inductors and capacitors thru the HF region, say 30 MHz max. I tend to be a bit lazy and like alligator clips, clip in the unknown and take a measurement. If you are not too sloppy you can get away with this! But I offer this up as a query... How simple you can put together a test set for measurement of components after doing a careful cal and get reasonable results? ________________________________ From: [email protected] <[email protected]> on behalf of tuckvk3cca <tuckvk3cca@...> Sent: Wednesday, August 7, 2019 10:49 PM To: [email protected] <[email protected]> Subject: Re: [nanovna-users] Measurement challenge A good exercise is to use your VNA to measure the very high unloaded Q of Toroid coils. I have good success with J. Oppenheimer's KN5L method for toroids with Q up to 230 using a single turn sense coil throigh the toroid connected to the VNA. Above all the measurement's agreement with theoretical values for Q and phase shifts is a good check of your calibration.Accurate measurement of unloaded high Q is by no means trivial. See the link to his webpage below: from my Samsung Galaxy smartphone. -------- Original message --------From: alan victor <avictor73@...> Date: 07/08/2019 21:45 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Measurement challenge I am not talking about calibration. THE CALIBRATION BY WHATEVER METHOD YOU DESIRE IS NOW DONE. Complete. Now we desire to measure some components. We are now in a position to use the NanoVNA as a component analyzer. Go measure... Alan |
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Re: Annotated nanoVNA menu diagram
Terrific addition to our knowledge of the NanoVNA.
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Thank you very much, Stuart K6YAZLos Angeles, USA -----Original Message-----
From: Oristo <ormpoa@...> To: nanovna-users <[email protected]> Sent: Wed, Aug 7, 2019 4:52 pm Subject: [nanovna-users] Annotated nanoVNA menu diagram That URL involves neither JavaScript nor cookies. It is my first CSS learning exercise and certainly buggy. For example, branches wrap badly on narrow displays. It displays OK on an iPad, but hovering requires a mouse.. Hovering a mouse pointer over some text boxes should pop up tooltip hints. Underlined TEXT have hyperlinks to longer descriptions in a plain HTML text file on the same website. TRACE and FORMAT entry annotations are yet to do. I will also investigate iPad support.. |
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Annotated nanoVNA menu diagram
That URL involves neither JavaScript nor cookies. It is my first CSS learning exercise and certainly buggy. For example, branches wrap badly on narrow displays. It displays OK on an iPad, but hovering requires a mouse.. Hovering a mouse pointer over some text boxes should pop up tooltip hints. Underlined TEXT have hyperlinks to longer descriptions in a plain HTML text file on the same website. TRACE and FORMAT entry annotations are yet to do. I will also investigate iPad support.. |
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Re: Measurement challenge
A good exercise is to use your VNA to measure the very high unloaded Q of Toroid? coils.?I have good success with J. Oppenheimer's KN5L method for toroids with Q up to 230 using a single turn sense coil throigh the toroid connected to the VNA.? Above all the measurement's agreement with theoretical values for Q and phase shifts is a good check of your calibration.Accurate measurement of unloaded high Q is by no means trivial.?See? the link to his webpage below: from my Samsung Galaxy smartphone.
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-------- Original message --------From: alan victor <avictor73@...> Date: 07/08/2019 21:45 (GMT+01:00)?To: [email protected] Subject: Re: [nanovna-users] Measurement challenge I am not talking about calibration. THE CALIBRATION BY WHATEVER METHOD YOU DESIRE IS NOW DONE. Complete. Now we desire to measure some components. We are now in a position to use the NanoVNA as a component analyzer. Go measure... Alan
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Problem with shorts and load in cal kits
Dr. David Kirkby from Kirkby Microwave Ltd
I expect that the short and load in all cal kits included in the NanoVNA
suffer this problem. When you mate two RF connectors you should *always* rotate the nut, and *not* the whole body of the connector. It is particularly important with precision connectors, but it is not a good idea to rotate the body of any connector. See this link click on ¡°making connections¡± then go to #4. 1. CRITICAL: Rotate only the connector nut - NOT THE DEVICE OR CONNECTOR BODY - until finger-tight, being careful not to cross the threads. Damage to both connectors will occur if the male center pin is allowed to rotate in the female contact fingers. Unfortunately it is impossible to do this on the shorts or loads in the male cal kit I have. (As I wrote earlier, the opens are best left of)f, but the problem would not exist with the opens as nothing touches the centre pin. Although it¡¯s possible to eliminate the problem with better quality loads, I see no way to eliminate the problem with the short unless the firmware was updated to consider the delay of the shorts. My own companies shorts, opens or loads don't suffer this problem. Whilst our loads could be used with a NanoVNA, the shorts would produce less ccurate calibrations due to the firmware limitations of the NanoVNA. I am unsure if this will make much practical difference on the NanoVNA, but CrossRF sell similar shorts as in the cal kit I received, *so having a spare short and a better quality load might be worth owning * i Dave. -- Dr. David Kirkby, |
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Re: A subtle omission... but with a work around.
Needed 3 hands. Had the Nano hanging from the cable and trying to hold it to move the markers. Good Idea though
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On 8/7/2019 4:42 PM, Peter Gottlieb wrote:
Take photos with your phone? |
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Re: A subtle omission... but with a work around.
Take photos with your phone?
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Peter On Aug 7, 2019, at 4:40 PM, Frank S <ka2fwc@...> wrote: |
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Re: A subtle omission... but with a work around.
While we are on this subject [BTW good rant Gary :-) ], do we really need that many save and recalls in cal and setup?
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Cal some of that memory be freed up to save a "display state? I was making a measurement outside on a G5RV I am putting back, and had to revert to a pen and paper to mark the resonances. And since we have given up on the SD card (because it was removed),? I could have save what was on the screen (to local memory), and gone to the computer to "download" it.? I could gave made better measurements on? my computer. Any thoughts? Frank On 8/7/2019 4:23 PM, Gary O'Neil wrote:
Now stay grounded gang... especially if you feel your NanoVNA is nothing short of junk because it falls short of meeting your routine anddemanding avocational requirements. |
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A subtle omission... but with a work around.
Now stay grounded gang... especially if you feel your NanoVNA is nothing short of junk because it falls short of meeting your routine anddemanding avocational requirements.
i know... I know... I forked over nearly $50 myself, so I feel your pain. I too am working hard at scrutinizing both the hardware and software of these devices, with the intent of contributing to the burdensome task of convincing the world that they are fools to invest such an outrageous price for something that improves their RF measurement capabilities by just a minimally few orders of magnitude, while for just a mere 30 dB more we all could own a piece of quality test equipment far more worthy of complaining about. EUREEKA! I believe I¡¯ve found it! There¡¯s no provision for saving data collected in the field other than being tethered to a laptop or a similar collection platform. OMG! Did we get ripped off or what??? I knew I should have sprang for the $45 K <Sheesh!> Oh well? As a wise person once told me many times over... Hind sight is 20/20. Live and learn I guess! That¡¯s the way the cookie crumbles... It¡¯s water over the dam. Another fine mess mess I¡¯ve gotten us into Ollie! I¡¯ve discovered however... that there¡¯s more than one way to skin a cat... even if it risks running out of clich¨¦s... or other perfectly unreasonable reasons to gripe. There actually is a means to gather data, disconnect from the DUT, relocate to your workstation area, connect the device to your computer, and finally download the data for use in the analysis software of your choosing. It¡¯s a bit of an inconvenience... BUT GIVE ME A BREAK!!! SHOULDN¡¯T I AT LEAST GET SOMETHING USEFUL FOR MY FIFTY BUCKS? On a humorous note however... here¡¯s the procedure. The NanoVNA must remain powered on at all times for this to work successfully. 1) With the data you wish to ¡°save¡± and port to your remotely located workstation, navigate to STIMULUS > PAUSE SWEEP. The data at the top of the screen will freeze to confirm you have paused the sweep. 2) Take care to not inadvertently alter the current state... either by the toggle switch or touchscreen, remove the NanoVNA from the DUT, observe that the desired data remains on the display, transport it to your workstation, hotplug the device into a USB port, then tap on the display a couple of times. This appears to initiate handshaking and establishes its connection with the workstation. 3) Launch NanoVNA Sharp on your workstation and click on connect. The result will (should) be the a displayed copy of the same data displayed on the NanoVNA. You can then use the facilities of NanoVNA Sharp to save a copy of the data to your workstation. To be clear, the data is not saved within the NanoVNA, and once the pause is lifted, or the device is power cycled, the data will be purged and replaced. A note to those who may exercise influence over the firmware developer, I have a suggestion that I think might add some value to the NanoVNA... ALTHOUGH IT WONT LIKELY EVEN COME CLOSE TO MAKING IT WORTH IT¡¯S OUTRAGEOUS 50 DOLLAR PRICETAG FOR CRYING OUT LOUD. GEESH! WHAT SHYSTERS!!! ... but to get back on my soapbox... It might be a relatively easy task to enable the firmware to allow the user to optionally store either CAL or measurement DATA in the 5 memory locations, in any mix or order of their choosing, by simply assigning C0, M1, C2,... etc. as an identifier in the vertical column, and providing the choice in the RECALL/SAVE menu. i.e. RECALL DATA, RECALL CAL, SAVE DATA, SAVE CAL. I¡¯m going to figure out how to get my $50 worth out of this extraordinarily sturdy, stable, accurate, capable and and incredibly useful piece of junk if it kills me... before I finally toss it where it belongs... in my shirt pocket... so I at least have it where I can get access to it without having to walk all the way across the room to make a measurement. Gads! What a rip off! How did I ever fall for this? Oh well... It¡¯s only money... Easy come, easy go! .... jus sayin¡¯ 72/73 Gary, N3GO |
Oristo
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