开云体育

The band that the primary problem is 40 meters; my xmtr is running on a
conventional power supply, not battery powered.

Yes, see message #401 from RF And Microwave Mag on this topic.

Alan

On Sat, Nov 16, 2019 at 05:04 PM, Larry Rothman wrote:

Herb,If you know a plumber** and can get a short length of 2 or 3 in Dia
copper pipe, stick some copper end-caps on it and you're good to go after
mounting the hardware. It's not as flimsy as an Altoids container and it's
easy to solder to.?

**Home Despot only has pipe in fixed lengths so a plumber is your best bet.?

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Thanks for the suggestion Larry,
The enclosure can be constructed in several ways and to me is the easy part. Disengaging the enclosure top from the inner conductor using readily available coaxial connectors is what I'm trying to wrap head around. I'm thinking of going with some type of friction contact connection like Kurt used. I'm sure my junk pile will turn up something.

- Herb

Oristo,
I ordered a NanoVNA-H which arrived today. In addition to now having a case, it has the battery display diode already installed and also has firmware 0.2.3.2 installed for upgrading without using a jumper to get into the DFU mode.

As for the Android NanoVNA WebApp (APK off-line version), it now works with USB-C Android 7.0+ devices that wouldn't work with my other NanoVNA. NanoVNA-H has the USB-C 1500 ohm resistors installed so I guess if I want to have my other NanoVNA recognized I'll have to install the resistors manually.

NanVNA-H didn't help my Chromebook, it still only recognizes the NanoVNA through the Webapp but not off-line using the APK app.

My wife's ZTE phone has android 7.0 and USB-C but from my research doesn't support OTG, so it doesn't recognize either NanoVNA. So before purchasing any bad ESN device do a web search and ensure it supports OTG. You would think all android 7.0+ smartphones do, but some don't.

- Herb

Has any thought been given to adding some marker math to both the NanoVNA firmware and also to VNA Saver? For example on a log mag plot it would really be handy to display the frequency and the level difference between two markers.

Sam
W3OHM

Herb,If you know a plumber** and can get a short length of 2 or 3 in Dia copper pipe, stick some copper end-caps on it and you're good to go after mounting the hardware. It's not as flimsy as an Altoids container and it's easy to solder to.?

**Home Despot only has pipe in fixed lengths so a plumber is your best bet.?
... Larry

Kurt Poulsen wrote:

"Just for the fun of it I measured a blue junkbox core as in my closed chamber as seen on the picture. "

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

Kurt,
The cylindrical test chamber is impressive. I'm sure the test data it yields is more realistic than the one loop procedure used by the OEM's. Is its construction from a test standard or is it per your own design?

So far I am happy with the numbers I am getting from my fixture. They have been repeatable for identically marked split ferrites.

I was thinking about building something similar to your cylindrical test chamber using a round altoids mint tin or a Tenny Tea tin. Still working on a convenient way to disengage the top cover from the inner conductor to change out solid ferrites.

- Herb

Hi Andy,

if you are able to do a little Math, you can use an S21 through measurement to measure an impedance.
Only issue: there is in the moment no software available for the nanovna to do the calculation. With the DG8SAQ VNWA the software supports this measurement as well as much other analysis modes. For the nanovna we will have to wait, if somebody implements it into the firmware (e.g. the Smith diagram for S21 could do the math) or software.

Some calculations: with 70dB noise flour and usable 60dB dynamic range of S21 (up to 300MHz) using a divider X to 50Ohm you could roughly calculated measure up to 50kOhm (60dB is a 1/1000 voltage divider, 50K Ohm and 50Ohm roughly give 1:1000)

shows that for high impedance S21 serious through and for low impedance S21 shunt through should be used. In between the S11 reflection method delivers good values.

vy73 de Karsten, DD1KT

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