开云体育

Just to guide you to the length that you need, check

Mike Willis
Register your consent or check if you are a registered Organ Donor at:

*beadonor.ca <>*

On 4/27/21 10:55 AM, gnarlodious@... wrote:

I searched the internet but found zero information on 2-Meter antenna cutting. Can I use the NanoVNA to cut a rod to the resonant length I want?
I have this new Larsen ? wave NMO mobile antenna, base loaded, on the center of a large (VW van) steel ground plane. From the screenshot below it is resonant at 142.8, do I have this right? I want trim the rod up spectrum to 145MHz, to get it into the lower amateur band. Am I right in assuming I can cut off pieces of the rod, using the NanoVNA to determine its resonant frequency? Any information is appreciated. Thought I had better ask before pulling out the Dremel.

You bet this works. One thing to think about is "how far do I cut" - typically, there's a bit of variation possible by sliding it up and down in the base, before you tighten the screws that hold it in. But as others say - "it's hard to make it longer once you've cut it". (If you do, a metal covered ball on the top of the antenna saves you <grin>)


Stand well back when you make the measurement (or sit inside the car where the feedline terminates).

To a first order, the resonant frequency is a linear function of the length. So measure the length now, measure the resonance. Cut a bit off, measure it, measure the resonance. Now you know how many 100kHz cutting a given length is worth. That should get you close.

(and if you foul up, going for broke on the first cut, there's always the "metal ball on the top of the antenna" - helps reduce P-static too

Your body can detune to antenna

Interesting. I am working some 20 feet (6 meters) from a large aluminum building. Can that also detune the antenna, considering the low power the nanoVNA emits?

One more thing. Do not stand close to the antenna when making the
measurement. You body can detune to antenna.
*Clyde K. Spencer*

You are right but cust very small pieces at a time. After each cut look at
the vswr or return loss curves to see where the current resonance is.

If you cut it too short there is no way to stretch it back.

Yes, I have done this.

73, Zack W9SZ

On Tue, Apr 27, 2021 at 12:55 PM <gnarlodious@...> wrote:

I searched the internet but found zero information on 2-Meter antenna
cutting. Can I use the NanoVNA to cut a rod to the resonant length I want?
I have this new Larsen ? wave NMO mobile antenna, base loaded, on the
center of a large (VW van) steel ground plane. From the screenshot below it
is resonant at 142.8, do I have this right? I want trim the rod up spectrum
to 145MHz, to get it into the lower amateur band. Am I right in assuming I
can cut off pieces of the rod, using the NanoVNA to determine its resonant
frequency? Any information is appreciated. Thought I had better ask before
pulling out the Dremel.

-- K5ZN

<>
Virus-free.
www.avg.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

I searched the internet but found zero information on 2-Meter antenna cutting. Can I use the NanoVNA to cut a rod to the resonant length I want?
I have this new Larsen ? wave NMO mobile antenna, base loaded, on the center of a large (VW van) steel ground plane. From the screenshot below it is resonant at 142.8, do I have this right? I want trim the rod up spectrum to 145MHz, to get it into the lower amateur band. Am I right in assuming I can cut off pieces of the rod, using the NanoVNA to determine its resonant frequency? Any information is appreciated. Thought I had better ask before pulling out the Dremel.

-- K5ZN

Download Absolute_Beginner_Guide_NanoVNA_v1_6.pdf
from the files section.

Martin 9A2JK

Thanks Roger...

yes, I meant F


what did I do wrong or not set to get the Smith chart as S11?

thanks and 73,, Tim

On Sun, Apr 25, 2021 at 07:21 PM, Tim Reimers KA4LFP wrote:

Hi everyone,

So I have a nano VNA-H and normally I use it with VNAsaver so I am less
familiar with the touch screen field use of the unit.

BTW - From your photos you do not have a NanoVNA-H. That is a NanoVNA-F which has different labelling on the connectors and on the traces.

Roger

On Sun, Apr 25, 2021 at 07:21 PM, Tim Reimers KA4LFP wrote:

What I don't understand is why the VNA was not changing impedance even
slightly....no "ring" being displayed on the Smith chart, etc.

If you look at your screen you will see your blue trace is set to S21. It needs to be S11 to measure the impedance on the Port 1 connector.

Roger

Hi everyone,

So I have a nano VNA-H and normally I use it with VNAsaver so I am less
familiar with the touch screen field use of the unit.

Today however I wanted to measure a couple of antennas out in the yard and
on my vehicles.

So I worked out how to set trace 0 to SWR in yellow and trace 1 to Smith
chart in blue.

I reset the calibration and ran a calibration at start and stop of 144-148
Mhz before taking it outside.

It then showed the lettering on the far left of the screen with a 0 beside
it showing that calibration number 0 was saved

As I screwed on and unscrewed the load you could watch the SWR change;
since sweep was not paused, the unit was sweeping constantly.

But the impedance never flickered even once from a blue triangle dead
centre in the Smith chart.

As I screwed into the various antennas (all 2 meter types) the SWR would
change slightly from one to the next, showing that 1 antenna had a low
point of just over 1.2:1 down at the bottom of the band and another antenna
had 1.2:1 at the top...

.... the point here being that it was actually measuring good but varying
SWR as I moved from one antenna to the next.


What I don't understand is why the VNA was not changing impedance even
slightly....no "ring" being displayed on the Smith chart, etc.

It was as if SWR on S11 was sweeping and reporting but impedance on S21 was
not sweeping and was stuck for some reason

I have never seen an antenna with an exactly 50 Ω impedance from one into
the band to the other much less multiple antennas and I don't think I was
seeing any now.




Never saw this happen when using VNAsaver but I wonder if I was doing
something wrong on the touch screen differently than the VNAsaver would
have done it?

Does anyone have any ideas?


Attached is a picture of that helps anyone diagnosed from the display what
was going on...

Sorry about the rotation on one image... blame my cell phone!

73, Tim KA4LFP



Prejudices are what fools use for reason. ~Voltaire

This problem is solved. I had to delete the file at
~/.config/NanoVNASaver/NanoVNASaver.ini
(MacOS Big Sur 11.2.3)
Apparently the file had been saved corrupted. Might help if someone put an error trap in there somewhere.

I've figured from trial and error that pressing the "Connect" button causes the crash on both ends. Until then, even though the NanoVNA is connected, it still responds to display touches.

It turns out that when this crash happens the nanoVNA device is also crashed and the display is unresponsive.

Now suddenly today whenever I click "Connect to Device" the application quits and I get a crash report. I don't know why after it was working well suddenly it would start quitting. I tried about 10 times just now. The final error I get is:

File "/usr/local/lib/python3.9/site-packages/NanoVNASaver/Version.py", line 48, in __gt__
l, r = self.data, other.data
AttributeError: 'NoneType' object has no attribute 'data'
Abort trap: 6

Hello Group,
I had a problem getting the latest Dislord firmware to run on my H4, which I solved, but now I have another strange issue. When the battery is fully charged and I first turn the VNA on it does not scan. If I hold one finger on the left side of the screen it will scan. Taking the unit out of the case helps some also. After it has been on for a few minutes it will scan more reliably and in the case. Today I found the problem and a complete solution.

The solution is to change the Power Setting from Auto, which I think defaults to 8 ma., to a smaller number. I tried 4 ma. and now the scanning problem completely goes away, even at full charge and in the case. I think that one of the chips in my VNA cannot handle the 8 ma setting (not sure what that does internally). I don't know how many other units may have a similar problem, but maybe the default setting should be something other than Auto. Now I really enjoy all the features of the new firmware. FYI

73, John, K9KA

How do I get the VSWR graph to show the 2 meter band? Nothing can be adjusted on it and no data shows up. I had several crashes so far and I don't know if it is working right on Big Sur.

On 4/23/21 4:03 PM, Jim Lux wrote:

On 4/23/21 2:28 PM, gnarlodious@... wrote:

/g/nanovna-users/message/5421

THANK YOU, I don't know why that was so hard to find!

Only differences were:
I didn't have to "Change PyQt restriction"
补苍诲…
I had to specify my exact Python version:
python3.9 -m pip install .

But it is running on Big Sur.

Now if I could only figure out how to use it! So far no data shows up on the graphics.

Did you "connect to device" (and does your device show up in the pulldown? (I'm not connected, so mine isn't showing).
Until you do that, nothing will happen.

Then click "Sweep" in the upper left subwindow, and new data should appear in the plots.

With the picture this time

Ahh yes, I routinely unlink pip and connect it to pip3, since python2 is EOL'ed anyway. I also routinely disable the MacOS system protection, I don't know if it matters in this case.

Yes it is working! I don't know what it all means but it is running on my vhf/uhf mobile! I guess I need to study the configuration files to make the output more readable.

-- K5ZN