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It's not just the Jog Switch it's also the way it is polled by the software.

Replacing the jog switch with push buttons improves the operation, mainly because at least you can feel the positive click as a confirmation, but it doesn't entirely fix it.

/g/nanovna-users/topic/34384144#3863

Regards,

Martin - G8JNJ

I am no longer in front of the device, but I am pretty sure there was CH0 preceding all 3 of the active trace readouts (RL, SWR and Smith).
Is there anything else that could have prevented the SWR trace to be non active?

Thanks for the input.

Some jog switches are of poor quality but you can determine if it's the firmware by flashing a different developer's version other than edy555 FW.Flash QRP's firmware - he does not have the marker freq change feature using the jog switch.
If the same thing happens, it's the jog switch - if not, it's the firmware.
Did you read edy555's release notes for the 0.5.0 release that I posted?

I think now, after reading posts about this same problem, that it is not the switch which causes problems, it is the jog wheel itself working illogically (in my opinion, that is)

If you have some spare fibreglass (FR4 PCB material or even an old PC board (strip the parts)) just create a small bracket to hold the SMA connectors in place.Cut, drill and slide the bracket over the square body of the SMA connectors.No dimensions given due to variations in spacing but it's a really simple build.Nothing more than a drill and small file is needed and you can separate the grounds easilyJust leave some copper around the openings to solder to...
...Larry

I've measured an 9.8k Ohm small THD resistor, using direct measurement on
CH0, and also the S21 method proposed by G3TXQ for measuring chokes:


[image: image.png]

It's obvious that the S21 method is giving much better results. This method
assumes both CH0 and CH1 impedances are 50+j0 Ohm, which is not quite true.
In order to improve that, I used two pcs 6dB attenuators before and after
the 9.8kOhm resistor which was inserted between CH0 and CH1 in series.
Of course, I've performed first a through calibration with the two
attenuators.

Ady YO2NAA

On Tue, Feb 18, 2020 at 10:27 AM Ady, YO2NAA via Groups.Io <yo2naa=
[email protected]> wrote:

Regarding the external bridge, I've asked Rune, the author of
NanoVNA-saver to add external bridge support.


NanoVNA-saver is already an amazing tool, I really appreciate the great
work of all developers of FW and SW related to NanoVNA.

Ady YO2NAA

On Sun, Feb 16, 2020 at 11:39 PM hwalker <herbwalker2476@...> wrote:

I agree with Kurt that the NanoVNA's inaccuracies above 300 ohms are
not that bad. I had the same frustrations with an HP Agilent 8753C

Network

Analyzer with 85046A S-Parameter Test Set. Once you get very far from 50
ohms its accuracy also suffers. An HP applications engineer I contacted
explained that's pretty much the nature of the beast for any low

impedance

50 ohm VNA, and there's no reason to expect any more of the NanoVNA. As
Kurt said, the test fixture also plays an important part in measurement
accuracy, especially above 1 MHz. Flying leads test fixtures basically
only work for quick checks in the kHz region.

Erik wrote a Matlab script,
/g/nanovna-users/message/7685, to use an external

bridge

to calibrate the NanoVNA at other than 50 ohms, but I never saw any
feedback from users who tried using it at 300, 1000, or higher

impedances.

There were actually about 34 messages in the "Using an external RF bridge
with NanoVNA " topic and I don't remember a definitive test procedure
write-up coming out of it.

- Herb

he SWR was always shown completely flat at the bottom of the screen and the
readout for that trace was in fact showing 1:1 as well along the whole trace.

1) be sure that the TRACE selected for SWR is using CHANNEL CH0
2) in SCALE, select whatever REFERENCE POSITION that you like
eg 1 x1
3) select an appropriate SCALE->SCALE/DIV
e.g. .2 x1 for 100 Ohm termination if calibrated for 50 Ohms

Regarding the external bridge, I've asked Rune, the author of
NanoVNA-saver to add external bridge support.


NanoVNA-saver is already an amazing tool, I really appreciate the great
work of all developers of FW and SW related to NanoVNA.

Ady YO2NAA

Hi,

I Ham friend of mine ordered a NavoVNA and he asked me to come over and help him understand how to check the SWR of his antennas. I am not yet very familiar with all the operational procedures of the NanoVNA except for what I could gathered here by reading other posts. But can't seem to remember a similar issue being brought up and a quick search did not help either. Plus I still need to order mine, but have not made up my mind between the v3.4 and the 4H, etc, so didn't have any experience at all playing with this device until now.

What I did first was set the start and stop frequencies (in this case 2-35MHz), then proceeded to make a calibration which included a reset and then seemed to go well on all three steps, as the markers for open, short and 50ohm where all showing in the correct position on the smith chart after the calibration was completed and saved. Afterwards I tried with a narrower frequency range (2-10MHz) then calibrated again, but the results where still the same as described bellow.

After connecting the antenna to CH-0 both the Smith chart and return loss traces seemed to be showing useful indications, but the trace corresponding to the SWR was always shown completely flat at the bottom of the screen and the readout for that trace was in fact showing 1:1 as well along the whole trace. This happened even when the Smith chart clearly was showing a reading of an impedance that was quite different than 50 ohms, plus capacitance or inductance. Besides it would be impossible for a single antenna to have 1:1 on the whole frequency range. Just as a test I connected a dummy load instead of the antenna and then the return loss trace would also be flat, and the smith chart would show the marker very close to where 50ohms would be expected to be.

So my question would be if I am missing to set up something else in order to be able to make the SWR trace work. I tried disabling all other traces but that did not solve anything either. Also not being yet very familiar with practical use of the device, I found that the Scale setting was a bit confusing as it only has the numbers and then a +1 field. Would this be used to define the per division dB value of the vertical scale markings?

Thank you in advance for any pointers.

On Mon, Feb 17, 2020 at 05:41 PM, <nanovnauser@...> wrote:

well looking at the link to owen duffys solution it looks like the ground is common to both connectors then?,cheers all 73
======================================================================

Owen only uses his NanoVNA up to 200 MHz. hugen intentionally separates CH0 and CH1 to improve isolation between those ports at high frequencies. Probably not anything you'll notice if all your testing is below 300 MHz. How much connecting the ports actually degrades the noise floor above 300 MHz is open to question, but hugen in past posts has recommended not doing so.



- Herb

Folks,
Always read the release notes for the version and development release of firmware you've flashed your device with.

In this case, edy555 documented the jog switch changes at this link:



"add lever operations that support shifting center freq, zoom span and marker search"

And they most likely survived to the current release.
This has been documented in my version of the User Guide since last November!

well looking at the link to owen duffys solution it looks like the ground is common to both connectors then?,cheers all 73

i think you missunderstand me,on nano the pcb it looks like the body of the sma connectors ie the ground are not electricaly conected to each other,thats what im' trying to find out.ie is is important to keep them seperate electricaly.?

On Mon, Feb 17, 2020 at 03:41 PM, Oristo wrote:

My understanding was the the jog switch affects whatever was most recently selected in menus.
For example, if marker 2 is selected, then jog switch would move marker 2. Then, if stimulus->start is selected, jog switch would affect start frequency....
=========================================================

Oristo,
Thai's my understanding also, but I don't have edy555's firmware version installed so I didn't want to guess. edy555's release notes never mentioned how to change between different jog switch behaviors. My preference would have been to use the jog switch to cycle selection, but he was probably constrained by the fact that depressing the jog switch brings up the on-screen menu and couldn't use that action to cycle selection.

- Herb

Changing the frequency using the jog switch is a feature using certain
firmware, but is disconcerting if you are used to the jog switch changing
marker movement.

My understanding was the the jog switch affects whatever was most recently selected in menus.
For example, if marker 2 is selected, then jog switch would move marker 2.
Then, if stimulus->start is selected, jog switch would affect start frequency....

Here is another similar set of data:

I think it supports Dave's general conclusion for resistors like 470 Ohms. This was done with a HP8714B VNA that is functionally very similar to the 8753.

However, it also shows more data points. This gives a look that again shows that the fine little nanoVNA is quite fine up to 300 MHz, good but noisy up to 900 MHz and (not shown here) challenging up to 1500 MHz. Nothing really new, but worth keeping in mind.

The spike at 225 MHz for the nano-VNA is repeatable and is an error. Others have seen this.

I did a quick look at a 5100 Ohm resistor, and neither the 8714 nor the nanoVNA was doing well with this. The 8714 was better in the 5 to 100 MHz range.

I have a N2PK VNA that makes very high quality measurements up to 60 MHz. It has an RF I-V adaptor

and

If you want to measure high or low impedance values, this box adds to the accuracy. But, to use this with the nanoVNA would require firmware changes and also the connection to a digital control line, that might be challenging.

73, Bob W7PUA

Shields must be connected as should the center conductors of any cable
extenders. Highly flexible cables are a good method to embody a connector
saver. Be fure to use good quality cables and connectors. With the cables
connected, the measurement plane (where the cal standards are placed and
measurements are made) becomes the end of the cables.

Dave - W?LEV

--

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

You may want to look at the elegant solution that Owen Duffy built at:


Dale W4OP

Note, with clearer screen captures:

50-ohm cal: S11 reads 304.88 ohms real as a folded dipole shoud (on the
right of the chart right where it sould be for 300-
ohms real)

300-ohm cal: S11 reads 53.5 ohms (in the center of the chart since you
have reset the cal position with a 300 ohm cal)
Also note that 53.5 ohms X 6 = 321-ohms, very close
to what you measured with the 50-ohm cal.

This is how a normalized chart works when calibrated to something other
than 50-ohms. You could just as well have taken the chart center as 1, or
unity. With a 50-ohm cal, the center becomes 50-ohms. With a 300-ohm cal,
the center becomes 300-ohms. The values in a normalized chart must be
multiplied by the system impedance of the cal. This is a good method to
make more meaningful measurements when dealing with extremely low and
extremely high impedances. However, the ultimate limitation will always be
the bridge or the directional coupler within the measurement instrument.

The HP 8753 uses a very carefully designed and meticulously machined
directional coupler to accomplish its published specifications (the HP
85047 S-Parameter Test Set mated with the 8753). I am continuously amazed
at how well the little NANOVNA (and all its variants - minus some clones)
compare to this very expensive piece of HP test gear! Credit to the
engineers who made it happen!!!!!!

As far as the additional dips in SWR, the antenna must be in free space to
show only resonances (the horizontal axis on the Smith Chart). Resonance
is defined as +jX = -jX, leaving nothing but real resistance which, for an
antenna, is the sum of ohmic losses in the conductors which make up the
antenna and the radiation resistance which is a 'magic' result of all
things electromagnetic ?? (you don't really want to know- *lots* of
calculus). The higher in frequency you go, the smaller geometries become,
and the easier it is to test in something resembling 'free space'. At FM
broadcast frequencies, its rather difficult without a semi-anechoic chamber
in which to test (read, lots of $$$$$$).

Dave - W?LEV

--

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

I use a generic unbranded one that came with a chinese tablet and it works fine with my Galaxy S7.

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

Same with me. I used the charging cable that came with my Xiaomi Mi9, with the USB C connector connected to the NanoVNA, and the USB A connector connected to this adapter bought on Amazon (sorry, I do not have anymore the URL...). Worked at the first try. Android version is 9.





Alberto





--
/*73 Alberto I2PHD*
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