开云体育

if your Android device doesn't support OTG,
or Google Play Store in the case of Chromebooks,
then neither serial terminal app will work.

It finally occurred to me that careful shopping e.g. on eBay
yields a fairly recent Android device with bad ESN cheaply
with less trouble than trying to update Android an older device

Hi Herb
Just for the fun of it I measured a blue junkbox core as in my closed chamber as seen on the picture. It can be calibrated on the inside with a SMA male ideal kit and therefore suited for the VNWA. I did measure with my VNWA and did use the custom trace as described where Mem1 is the empty test chamber and Mem2 with blue core. You can see how fine the shorting rod in the test chamber run along the circumference of the smith chart. The cross over where the ImagZ turns capacitive is also seen. The RealZ is of Mem2 is following the Custom trace (the difference) as real Z of the rod is so to speak 0 ohm. I same the Custom trace to a s1p files and imported it the the NanoVNA-saver and also imported the Mem2 s1p files (core + rod) and you can see how big the impact is canceling the rod impedance
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af hwalker
Sendt: 16. november 2019 19:12
Til: [email protected]
Emne: Re: [nanovna-users] NanoVNA-Saver 0.2.0 #Ferrite_Impedance

Kurt,
After a good nights sleep I and a second mulling over your post it became even clearer that I had deceived myself into thinking I could calibrate out the test fixture by treating it as an extension to the coaxial line and calibrating at the outside side. The reference sweep using a 50 ohm load looked convincing, but one of the gotcha's with a VNA is that if you perform a bad calibration it will look great compared against itself.

I re-cal'd this morning at the end of the connecting cable and used Rune's software to take a reference sweep of the fixture terminated with a short. I took another sweep with the ferrite under test installed. I visually subtracted the reference trace impedance values at 10 MHz, 25 MHz, 100 MHz and 250 MHz from the live trace values and compared them to the corresponding manufacturer's table (see attachment).

The comparison data was much better than the previous run. The data points at 100 MHz and 250 MHz were especially close to the manufacturer's table.

Thanks for lending your keen eye to this. As they say, "There is no substitute for experience". Now I wonder if I could get Rune to add some trace math to his program …

- Herb

Kurt Poulsen wrote:

"Actually if you make a.sweep of the test fixture without the clamp, and in the NanoVNA-saver display r+jx then you have a graph for the real impedance to print"

---------------------------------------------------------------------------------------------------------------------------------------

I discovered the same thing empirically when I tried to cross check my results from Run'e program using the NanoVNA-Sharp V3 app. NanoVNA-Sharp only has a r+jx display that I could use to cross check Rune's program. In that display format 25 MH, 100 MHz, and 250 MHz were in the ballpark with the manufacture's 4 point tabular data. 10 MHz was a bit low at 40 ohms instead of 90 ohms.

Glad your recommendation regarding r+jx display aligns with my empirical (read playing around with things) finding. I need to test about 10 samples each of different types of snap-on ferrites before I feel confident with the test set-up and procedure.

Again, many thanks for your input.

- Herb

Hi Herb
Great, I am pleased to hear the progress. Actually if you male as sweep of the test fixture without the clamp and in the NanoVNA-saver display r+jx then you have a graph for the rod impedance to print. Doing the same with the clamp fitted you can subtract the two readings directly and plot it manually.
If the NanoVNA-saver had a feature for saving data files (r + jx) then a spreadsheet quickly could draw the graph by subtracting. Else it is not difficult to do the S to Z in a spreadsheet
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af hwalker
Sendt: 16. november 2019 19:12
Til: [email protected]
Emne: Re: [nanovna-users] NanoVNA-Saver 0.2.0 #Ferrite_Impedance

Kurt,
After a good nights sleep I and a second mulling over your post it became even clearer that I had deceived myself into thinking I could calibrate out the test fixture by treating it as an extension to the coaxial line and calibrating at the outside side. The reference sweep using a 50 ohm load looked convincing, but one of the gotcha's with a VNA is that if you perform a bad calibration it will look great compared against itself.

I re-cal'd this morning at the end of the connecting cable and used Rune's software to take a reference sweep of the fixture terminated with a short. I took another sweep with the ferrite under test installed. I visually subtracted the reference trace impedance values at 10 MHz, 25 MHz, 100 MHz and 250 MHz from the live trace values and compared them to the corresponding manufacturer's table (see attachment).

The comparison data was much better than the previous run. The data points at 100 MHz and 250 MHz were especially close to the manufacturer's table.

Thanks for lending your keen eye to this. As they say, "There is no substitute for experience". Now I wonder if I could get Rune to add some trace math to his program …

- Herb

Howdy Ron,
Properly calibrated, the nano should give you much better accuracy than even a very good SWR meter, because a VNA calibrates at many points (101 for the nano) across a frequency span, versus an SWR meter that is calibrated at one point only. And the VNA uses a resistance bridge that is much flatter than the directional coupler used in typical SWR meters. Some things to consider.

1a. You can perform a calibration on the nano thru your existing cables and connectors, e.g., the input cable, the bypassed tuner/meter; and on its output side, PL259 short, open, and load. For the load, use a 100-watt+ dummy load, so you can apply radio TX power and calibrate your cross-needle meter. Then replace the radio with the nano, and calibrate it with the exact same setup. This will give you a calibration through the tuner box and let the nano see what the radio sees.
OR 1b: Cal your cross-needle with a 50-ohm dummy load; Cal your nano at a SMA-SO239 adapter+same dummy load (and PL259 short and open); then move the antenna cable between them; i.e., in both cases the ant coax replaces the dummy load. This will measure antenna without the tuner being in the system.

But also consider:
2. SWR meter indication may rise with increased power, due to all the those bare wires in the tuner (several inches long even in bypass) having some inductive and capacitive coupling within the tuner. On tuner/meter+dummy load, crank the radio's power & frequency up & down. There will be some non-linearity caused both by the directional coupler (probably a Bruene), and some caused by unshielded wires in the tuner. My 3 tuner/meters will vary from about 1.3:1 on 80, 1:1 on 20 (where I calibrate), to 1.7:1 on 10 meters, on a dummy load, and rise a little more with increasing power.

3. Similarly, on antenna, SWR may rise a little with increased power, due to antenna coupling with ground and other conductors in its near-field environment. Set the radio's freq at the antenna's resonance then crank the power up; if increasing power raises the SWR (more than it did with the dummy load), then you know you have some antenna coupling effect (RF induced in nearby conductors causing re-radiation back to antenna, changing its feed-point impedance -- this effect shouldn't increase with power level, but alas, in practice, it sometimes does).

Anyway, my points are that you need to calibrate the nano with the same (as close as possible) setup as the SWR meter uses, and also consider that the power output of the nano is something like 0.1 milliwatt, causing very little coupling effects; versus the 10-1500 watts the radio/amp puts out, causing considerable coupling effects. In addition to all the other possible errors! Like Bruene coupler vs. resistance bridge, grounded meter vs. floating, etc etc.

73, --kv5r

Roger!

What band are you doing your testing on? Also, is your xmtr running on AC power or battery?

Tom AE5I

you can use impedance transformer. Transformer impedance ratio is a square of turns ratio (or voltage ratio).

For example, RF transformer with 1:2 turns ratio will works as 1:4 impedance ratio.

If you are intending on tuning a 6-cavity BPBR set of 'cans' for 6, 2, or
70-cm using the NANOVNA and intending to obtain what is typical isolation
with a 6-can duplexer, the NANOVNA does not have enough dynamic range to
measure 100+ dB of isolation between TR/RX frequencies. Look at the
published specifications and you will understand. It's a great instrument,
certainly for the price, but it not an HP 8753C which is capable of 100+ dB
of dynamic range to tune these sort of cavities (I've tuned many using that
instrument).

Dave - W?LEV

On Sat, Nov 16, 2019 at 1:17 PM Corneliu via Groups.Io <coralenka=
[email protected]> wrote:

Thanks very much!

Trimis din Yahoo Mail pe Android

Pe s?m., nov. 16, 2019 la 14:45, neb40gsm via Groups.Io<neb40gsm=
[email protected]> a scris: Hi Corneliu,

The software is under development, but if you are interested you can
get it from here:

neb

--

*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*

Kurt,
After a good nights sleep I and a second mulling over your post it became even clearer that I had deceived myself into thinking I could calibrate out the test fixture by treating it as an extension to the coaxial line and calibrating at the outside side. The reference sweep using a 50 ohm load looked convincing, but one of the gotcha's with a VNA is that if you perform a bad calibration it will look great compared against itself.

I re-cal'd this morning at the end of the connecting cable and used Rune's software to take a reference sweep of the fixture terminated with a short. I took another sweep with the ferrite under test installed. I visually subtracted the reference trace impedance values at 10 MHz, 25 MHz, 100 MHz and 250 MHz from the live trace values and compared them to the corresponding manufacturer's table (see attachment).

The comparison data was much better than the previous run. The data points at 100 MHz and 250 MHz were especially close to the manufacturer's table.

Thanks for lending your keen eye to this. As they say, "There is no substitute for experience". Now I wonder if I could get Rune to add some trace math to his program …

- Herb

Just wondering about how to increase the highest value of impedance
measurements. Since it tops out at about 600 ohms in HF
I was thinking along the lines of resistive shunt and back calculating.

Without fully working thru the math, I >>guess<< that back-calculating shunt
would lack better accuracy (S/N) than straight measurement.

I wonder how others tackle the problem?

A green (not blue) ~US$10 reflection bridge
e.g. from eBay
with matched SMA references (want a matched pair to calibrate nanoVNA CH1)

Thanks for the reminder and suggestions. Yes, I have calibrated using my
cables to connect with my antenna. This users group is great!

Dick,
I forgot to add that currently all firmware releases for the NanoVNA-F are single sourced by BH5HNU. One of the advantages of the smaller NanoVNA is it has a number of creative firmware developers who continually push the limits of its measurement capabilities. Features that these developers have added to the NanoVNA, such as TDR measurement, extending the frequency range to 10 kHz and 1 Hz frequency resolution, will mostly likely only be added to the NanoVNA-F through direct request to BH5HNU.

- Herb

Dick,
The Nano-F has different firmware that is not compatible with the smaller NanoVNA. You can still perform TDR measurements from the PC side using NanoVNA-Saver or NanoVNA-Sharp. You can also make a request to BH5HNU on the NanoVNA-F group forum ( /g/nanovna-f) to add TDR to a future firmware release.

- Herb

Accidental issues are not the end of the world - just turn it in again.

I have a NanoVNA-F (Firmware Ver. 0.0.3). I also have
a Users Guide that talks about the TDR function.

I cannot find that function on this NanoVNA. Was the
TDR function a Firmware Update ?

Thanks for the help on this.

Dick, W1KSZ

An electronic switch that has to be pressed for a second or two to turn the device on or off would be even better in order to prevent accidental issues.?



On Sat, 16 Nov 2019 at 10:13 AM, Harold Farrenkopf via Groups.Io<hfarrenkopf@...> wrote: I knew they were crappy switches and replaced mine with a good quality toggle switch while I installed it in the printed case i bought. I replaced the jog switch as well and mounted a small slide switch where the jog switch was to use for the firmware writing (recessed so it needs a small rod/tool to move it)

Please be aware you may be able to calibrate till 1500MHz but the measurement of anything different from SOL can still be completely wrong due to non linearity errors

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

Ron,

Have you calibrated he nano with a calibration standard of the same style that your antenna connector is? I.E if your cable connected to the radio has a male UHF connector, your nano needs to be calibrated with a male uhf set. If you calibrating with the SMA set and then attaching an adaptor or adaptor cable to connect to the antenna cable the readings will be off. A VNA no matter if it cost $50 or $100k always needs to be calibrated at the plane of measurement. Here, the plane of measurement is the point you attaching your antenna cable. Since the VNA looks not only at forward and reflected power but also at phase not calibrating it right will cause errors in either direction...i.e. either read too good or too bad. You can make male calibration sets yourself that are adequate and only have minute errors vs commercial sets. U-tube has quite a few instruction videos how to do it.

John,
Try Dennis Real's firmware release for an even better antenna analyser experience. Search for forum member reald here or on GitHub.?



On Sat, 16 Nov 2019 at 11:00 AM, John Ackermann N8UR<jra@...> wrote: Thanks!? That seems like a really useful combination then -- simple,
easy to read display on the go, with full power when you're connected to
a host.

Thanks! That seems like a really useful combination then -- simple,
easy to read display on the go, with full power when you're connected to
a host.