Re: NanoVNA-Web-Client, problem with Chromebook
On 1/9/20 9:32 PM, hwalker wrote: Does NanoVNA-saver run O.K. under Gallium? ???? NanoVNA-saver is written in Python.? Gallium is based on/compatible with Xubuntu, and Python is available in the Ubuntu repositories.? So, I would assume that NanoVNA-saver would run just fine under Gallium, with one caveat:? Gallium only runs on Chrome devices based on Intel or AMD processors, but does not run on ARM processors.? If you don't know what sort of processor is in your Chromebook, check here:
|
We started selling nanoVNA-H4 using STM32F303CCT6 and 4-inch LCD
|
Re: nanovna that continues to indicate 50 ohms when S11 is open
Loads are good. When I calibrate my nanovna-f with it everything’s works perfect. Just to be sure I have measured them and they are correct.
|
Re: New version of NanoVNA-Saver: 0.2.1
Hi Rune,
Thank you very much for the wonderful nanovna-saver software. Python isn't my forte but I managed to install it on my Debian laptops without much of a hassle (Python3.7 was already installed in Debian 10/Buster).
I am fairly new to VNAs in general and the NanoVNA environment specifically, so please forgive my ignorance if what I'm asking is already present in nanovna-saver.
I'm helping a friend to determine the effectiveness of common-mode chokes. I created a test-jig (as shown on ) to perform 2-port measurements. For chokes to be effective we want to get an idea of the Resistive component at a given frequency. Currently I don't see an S21 graph in nanovna-saver that will show this. I know I can make use of S21 Phase (deg) and S21 LogMag / Gain graphs to compute S21 R, X and Z but I wonder if the latter values (R X and Z) can be added to the list of graphs? Alternatively, would it be possible to create a 'custom' graph so that the user can post-process data and draw their own graph based on their own formulas?
Keep up the good work and happy 2020.
Regards,
marcel VK2CEL
|
Re: NanoVNA-Web-Client, problem with Chromebook
Does NanoVNA-saver run O.K. under Gallium?
- Herb[
|
Re: Measuring resonance from coax far end.
On 1/9/20 3:55 PM, WB2UAQ wrote: I bet SimSmith will make it even easier but right now I don't have the patience to sit still and figure out how to run it:) ???? You won't need any patience, it's amazingly simple.? Like drop in an LC element between two impedances, and it automatically calculates appropriate values to match.? Tell it you want a high pass instead of a low pass, and it automatically recalculates.
|
Re: NanoVNA-Web-Client, problem with Chromebook
Have not found anything on the net that indicates Android apps will run under Gallium. Anbox, which "puts the Android operating system in a container" runs under various Linux distros, but the scuttlebutt is that it has problems running inside Gallium.
|
Re: Measuring resonance from coax far end.
Thanks Hans for taking the time to explain your methods. I have been doing a lot of testing with my Nano since I rec'd it at the end of August. The s1p formatted data has been most useful. I mainly measure impedance with the Nano. Then have done some impedance matching with good results giving me confidence that the measurements are pretty good. If you measure the Z to be matched, calculate a matching circuit, build it and the SWR is 1.0:1. I have not used SimSmith but have down loaded it. Years ago (some time in the early 90's possibly) I learned how to calculate the matching elements using an HP32S calculator that can store and run simple conversion formulas. I programmed in the series to parallel and parallel to series converters and with them it is possible to determine the L's and C's required. I bet SimSmith will make it even easier but right now I don't have the patience to sit still and figure out how to run it:)
In regard to the EFHW, the latest antenna craze, I wondered about the feed point Z of 67 feet of wire running from the ground up to a tree a steep angle (>45 degs for sure). I used an ancient General Radio GR-821A and did a direct measurement against a ground stake. The GR-821A can measure high impedances directly and it came up with 3700 to 3900 ohms shunted by about 8.5 pF at 7 MHz. I ran some tests at three locations that had I, am hoping, three different ground conductivities. The results were very close to each other. Using a transformer (2 turn primary and 18 turn secondary) I have great results on 40 and 20 meters.
Wish I could help out Chris with his questions. I have been where he is now. Takes some study and it will all fall into place. I am very cautious about making a solid conclusion due to common mode current on the outside of the coax line from measured impedances. One small change to how the transmssion line is routed and how long it is and what the mismatch at the antenna is will have an impact. What I have come to learn is that when the feed point impedance is low there is less common mode current and therefore less impact to the impedance measured. When the Z is high, then there is more of a tendency for current to flow on the coax braid and the impedance measured will be impacted. I have see the Z move by simply moving how the coax is placed or coiled up, etc..
73, Pete
|
Re: NanoVNA-Web-Client, problem with Chromebook
Yup!
I have an old Acer C710 with Gallium Linux installed. Opened the Chrome browser under Gallium Linux, enabled the experimental web thingy in chrome://flags, loaded the NanoVNA Web Client...then I had to root around a bit to figure out the device path for the Nano (for me, it is ttyACM0), selected that (from the 20 or so options) in the connect box, and Voila!
|
166 ?H is a pretty large inductor and likely has a pretty low self resonant
frequency. Try 'de-Qing" the inductor by parallelling it with a 4.7 k to
10 k carbon resistor. If those work, increase the resistance a bit.
Dave - W?LEV
toggle quoted message
Show quoted text
On Thu, Jan 9, 2020 at 7:26 PM Leif M <sala.nimi@...> wrote: I post this if anyone is interested. 80MHz seems to be quite a lot for
this kind of construction and transistor.
I put some aluminium tape on input side parts. Perhaps it made the S11
plot a little cleaner. Below 200-300Mhz the S11 is still not very smooth.
(ragged I think is a good word for it.)
I attached schematic and new results from VnaSaver. I took a photo of the
amplifier, but the whole thing is so untidy I leave it off.
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
|
Re: NanoVNA-Web-Client, problem with Chromebook
entilleser via Groups.Io wrote: Ah... Got it. I have not heard good things about the Chromebook implementation of Android apps - slow, buggy, &c... GalliumOS for the Chromebook isn't trying to run Android apps under ChromeOS. It's a full and fairly robust distribution of Linux which is either available as a boot option, or completely replaces the entire ChromeOS nightmare. It makes an "obsolete" and "unsupportable, just throw it in the recycle bin and buy a new one" Chromebook into a very usable and handy Linux notebook; decent screen, light in weight, blazingly fast to boot up, and very compatible with about any Linux software available. -- wes will n9kdy
|
Here is an alternative. It may not be precise but can give you an idea of
the loss. First you need to have access to the antenna end of the
transmission line.
1. Fully calibrate the NANOVNA using your best OS for the desired frequency
range.
2. Connect the short to the VNA and note the return loss using LOGMAG.
3. install the short at the antenna end.
4.Connect the VNA to the station end of the transmission line
5. Use the LOGMAG and perform a sweep
6. Note the return loss.
7. divide the return loss by 2.
This will get you close.
*Clyde K. Spencer*
toggle quoted message
Show quoted text
On Thu, Jan 9, 2020 at 2:31 PM Leif M <sala.nimi@...> wrote: I am in no way an expert, but if you connect your cable between CH0 and
CH1, you will see the loss (or gain) at every frequency. You have to
calibrate your VNA fully first .
|
I am in no way an expert, but if you connect your cable between CH0 and CH1, you will see the loss (or gain) at every frequency. You have to calibrate your VNA fully first .
|
Re: RF Demo Kit Testing tutorial released
On Thu, Jan 9, 2020 at 11:18 AM, <reuterr@...> wrote: Comparing with your screen shot of *Test field 8* I assume,
that you did not made a *Calibration* with the RF Demo Kit *Test fields
13-15*. Hello Rudi, I have made it. I can redo the measurement with the FA5, but as I told you, we tested it with the Rohode&Schwarz with calibrating and the results are comarable.
|
I post this if anyone is interested. 80MHz seems to be quite a lot for this kind of construction and transistor.
I put some aluminium tape on input side parts. Perhaps it made the S11 plot a little cleaner. Below 200-300Mhz the S11 is still not very smooth. (ragged I think is a good word for it.)
I attached schematic and new results from VnaSaver. I took a photo of the amplifier, but the whole thing is so untidy I leave it off.
|
Hi all,how do i measure the loss on a long run of coax using the nanovna,ive about a 60ft run i want to check at hf,cheers .
|
Re: nanovna that continues to indicate 50 ohms when S11 is open
Check all your cal loads to make sure they have the correct impedance.
|
Re: nanovna that continues to indicate 50 ohms when S11 is open
Yes, I have also done a reset before calibration
|
Re: NanoVNA-Web-Client, problem with Chromebook
From hwalker: "The issue with Chromebooks has been that with the latest Chrome update you can connect the NanoVNA with the web based application, but not off-line using the Google Play Store android application."
Ah... Got it. I have not heard good things about the Chromebook implementation of Android apps - slow, buggy, &c...
|
Re: First PCB pictures of the V2
“Crosstalk between microstrips” — one trick used by at least one up-market spectrum analysers is to put small “bridges” of ferrite, across the microstrip. These are equivalent to the ferrite beads put onto thin coax and will attenuate signals flowing on the outside of the microstrip. The exact ferrite is not critical providing it has loss at GHz. I have also experienced the problem where a “well-designed” amplifier stage becomes unstable when put into a metal box. The eigenvalues of a box with a few holes and one side made from the PCB are difficult to calculate. The overall stability is even more difficult to calculate. (Was said to be impossible by the lecturer in my undergraduate course.) The simple solution - take an old medium wave radio and extract the ferrite rod from the aerial coil. Glue it, or a part of it, to the inside of the box, well clear of the microwave components. These ferrites are very lossy at even VHF, never mind GHz. If I use a metal box for RF screening I always ask myself the question “where does RF energy, radiated by the components and microstrips, ends up?”
Brian 5B4AHW
toggle quoted message
Show quoted text
On 9 Jan 2020, at 11:13, Gabriel Tenma White <OwOwOwOwO123@...> wrote:
Tried a TCM1-63AX (had these in stock), it gave really strange S11 graphs and not good directivity. Might investigate it further.
Crosstalk between microstrips or grounded CPW is low in theory, but my experience is it turns to crap as soon as you have nearby metal objects to reflect the radiated signals, or put the board in a metal enclosure. The LCD is mounted right above the PCB so the whole thing forms a nice waveguide for leakage to travel. The remaining bits of leakage seen in the pictures is still due to radiation (maybe not the SMA connectors but shield can leakage) because I can affect it by putting my hand near the board. Past designs didn't achieve good system dynamic range even with shield cans because of the remaining leakage from the SMA connector center pin, so switching to this style of connector (and having the connector footprint in the shield can) was the only way to fix it.
The receiver linearity is important because nonlinearity causes errors that can't be removed by calibration. For example the IAM-81008 mixer has P1dB(in) of -15dBm and IP3(in) of -6dBm, but if you operate at -25dBm (which is 10dB below compression) your third order error power is -6 - (-6 - -25)*3 = -63dBm, which is 38dB below the signal. That's a EVM (error vector magnitude) of 1.25% which is just on the edge of being acceptable. Nonlinearity doesn't just generate harmonics, it also causes amplitude/phase error in the fundamental signal. The rule of thumb is at least 20dB below IP3, and also at least 10dB below P1dB. The way to check for linearity error is to measure a short length of low loss coax (after calibration) and check that it circles the smith chart as expected. I think there was a thread here that showed errors in the current Nano in this setup because of the low IP3 mixer (SA612) used. I'll try the BGA616 for the gain block which has good enough IP3 and P1dB.
I've done FPGA based VNAs before at a different company and I find it much easier to deal with than a microcontroller. All timings are deterministic, and you can coordinate things to happen at cycle accurate times with respect to the reference clock. Spartan 6 starts at $4, so as soon as the required MCU gets close to that price I'd just switch to the FPGA :) Optimal IF frequency is somewhere between 1 to 5 MHz (based on ADF435x noise skirt).
I'd like to see your coupler design; can you post the title of your paper?
|
Jim Allyn - N7JA
Roger Need