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Hi Dave,

S21 is the gray, I think (the not yellow one -- I'm color blind) print at the top right of the screen in the last two images I posted. It's line is flat at 0 dB across the frequency range with the test rig shorted and gives the unusual curve I showed when the filter is used. Connecting the Ports 0 & 1 of the VNA together (without the test rig) also show 0 dB flat across the frequency range. Is that what you meant?

Many thanks.

Mitch NK3H

These plots compare reference impedance renormalization using S11, S21, S12, and S22 (yellow) with using just S11 and S21 (cyan). Shown are results for two different 10.7 MHz Murata ceramic filters renormalized from 50 to 330 ohms. The signal passband is 10.6 to 10.8 MHz. The plots demonstrate that when using a NanoVNA that can measure only S11 and S21, you can benefit by reversing the filter and measuring S22 and S12 as well.

Download the S-parameter plotter with renormalization and Y21 method:



Brian

Please measure S21 instead of S11 using the NANOVNA! All S11 tells us is
the match (which is pretty bad!).

Dave - W?LEV

On Thu, Mar 13, 2025 at 12:14?AM Mitch NK3H via groups.io <mitch=
[email protected]> wrote:

Thank you Alan. I've attached an image of the whole setup including the
filter, the test rig and the VNA. Please note that I'm just using hookup
wire to connect the filter to the testing rig--no SMA or BNC connectors. It
made no visible difference when testing on the scope using the wires or
direct to a leg of the input and output capacitors. The other image is with
a wire connecting the input to the output of the test right. The result is
0db flat across the range for S21. The signal generator has 50 ohm output
impedance, and the scope has a very high impedance input. Not sure about
the VNA. I tried the setup with a 50 ohm resistor to ground on the filter
output and found no difference in the VNA behavior. Thanks for your help.
73, Mitch NK3H

--

*Dave - W?LEV*


--
Dave - W?LEV

Thank you Alan. I've attached an image of the whole setup including the filter, the test rig and the VNA. Please note that I'm just using hookup wire to connect the filter to the testing rig--no SMA or BNC connectors. It made no visible difference when testing on the scope using the wires or direct to a leg of the input and output capacitors. The other image is with a wire connecting the input to the output of the test right. The result is 0db flat across the range for S21. The signal generator has 50 ohm output impedance, and the scope has a very high impedance input. Not sure about the VNA. I tried the setup with a 50 ohm resistor to ground on the filter output and found no difference in the VNA behavior. Thanks for your help. 73, Mitch NK3H

1) Please post a schematic (already requested).

2) Did you measure the individual components before constructing the
filter with them?

3) We assume the filter is designed for 50-ohms in and out? (already
assumed)

4) Is the dielectric of the capacitors appropriate for the frequency range?

5) Instead of using the o'scope and FFT, please give us a plot of S21
using the NANOVNA. Please use SAVER (or equivalent) to accomplish your
sweep with more points than are available on the native instrument.

6) If your signal generator can sweep, you can also measure the filter
response with that. A flat output noise generator can also be used instead
of the swept sig. gen.

Dave - W?LEV

On Wed, Mar 12, 2025 at 11:11?PM Mitch NK3H via groups.io <mitch=
[email protected]> wrote:

I've searched through the message list looking for symptoms similar to
mine and didn't find anything. I'm somewhat new to this and would
appreciate any help you can offer.

I've been trying to get my NanoVNA-F (firmware 1.0.5) to show the results
of a 40-meter low pass filter I've built. I know I'm doing something wrong
here but can't figure it out. The VNA image is calibrated (including
pass-thru), set for the range 6.5 to 29 MHz and logmag S21. Shouldn't this
give a flat area leading up to the design frequency followed by a
significant roll off through the remainder of the frequency range? My setup
is very similar to W2AEW's YouTube demonstration of the NanoVNA with a LPF
but gives entirely different results. The image is entirely different, with
very large insertion loss and a steep area of suppression peaking at 11 MHz
followed by a steep recovery.

I worried that my filter wasn't what I thought it was so I tested it with
a 7 MHz square wave, looking at input and output with the FFT function of
my 'scope. The before and after images show several things: (1) the square
wave (yellow trace) is hardly a square wave. It wasn't much of one before
attaching to the input of the filter but it's definitely loaded and
distorted by the filter. (I can live with the distortion in the test, since
the filter is supposed to reduce the high freq distortion anyway, right?)
(2) The purple trace is the filter output--pretty nice sine wave. (3) The
FFT shows a good 40+ db suppression of the harmonics, especially the odd
numbers. So the filter seems to be doing its job.

There may be some things not right about my testing of the filter using
signal generator and oscilloscope -- I'm new at this. For example, the
shoulder on the filter output at about 10 MHz is troublesome, but still the
logmag S21 output shouldn't be affected, should it?

Any help in understanding why my results look as they do would be greatly
appreciated.

Best & 73,

Mitch NK3H

--

*Dave - W?LEV*


--
Dave - W?LEV

One last item, on your scope pulse gen measurement. Dial your pulse gen
back to 100 kHz, you should see the fidelity of the square wave as measured
at the output load termination R. As you increase frequency, the fidelity of the
square wave will suffer, of course, and for the most part you should see a sine wave
attenuated at the pulse input frequency.

Also, I would do your setup and cal over a frequency range of 100 kHz to 30 MHz.
This way you should see the FLAT DC response of the filter, well below its cutoff and then
see its roll off and ultimate attenuation.

Confirmed and looks ok... Mitch.

Assume that your layout is such that the inductors are ideally non coupled to each other, ideal each at right angles.
The connectors are panel mount? Soldered their body to ground and center conductor to the input pads. A photo
of you filter card would be useful. In any case, re calibrate and then check your calibration is ok by checking your
through cable fiving a S21 of nearly 0 dB and a S11 of at least 20 dB or better.

Great. Give a few moments to run a check on what we should be seeing.

Here's the filter I built. Laid out on copper plated board. Capacitors are all grounded on the copper ground plane. Thanks. Mitch NK3H

Please post a schematic of your filter. Assume it is designed to operate in a 50 ohm system.

I've searched through the message list looking for symptoms similar to mine and didn't find anything. I'm somewhat new to this and would appreciate any help you can offer.

I've been trying to get my NanoVNA-F (firmware 1.0.5) to show the results of a 40-meter low pass filter I've built. I know I'm doing something wrong here but can't figure it out. The VNA image is calibrated (including pass-thru), set for the range 6.5 to 29 MHz and logmag S21. Shouldn't this give a flat area leading up to the design frequency followed by a significant roll off through the remainder of the frequency range? My setup is very similar to W2AEW's YouTube demonstration of the NanoVNA with a LPF but gives entirely different results. The image is entirely different, with very large insertion loss and a steep area of suppression peaking at 11 MHz followed by a steep recovery.

I worried that my filter wasn't what I thought it was so I tested it with a 7 MHz square wave, looking at input and output with the FFT function of my 'scope. The before and after images show several things: (1) the square wave (yellow trace) is hardly a square wave. It wasn't much of one before attaching to the input of the filter but it's definitely loaded and distorted by the filter. (I can live with the distortion in the test, since the filter is supposed to reduce the high freq distortion anyway, right?) (2) The purple trace is the filter output--pretty nice sine wave. (3) The FFT shows a good 40+ db suppression of the harmonics, especially the odd numbers. So the filter seems to be doing its job.

There may be some things not right about my testing of the filter using signal generator and oscilloscope -- I'm new at this. For example, the shoulder on the filter output at about 10 MHz is troublesome, but still the logmag S21 output shouldn't be affected, should it?

Any help in understanding why my results look as they do would be greatly appreciated.

Best & 73,

Mitch NK3H

1 Hour... Good info... Excellent Intro.... Time well spent.... From R&S.

I would return it. Alternatively check with the manufacturer if your unit
is genuine and that their warranty policy is.

On Tue, 11 Mar 2025 at 23:23, alsodanev2 via groups.io <alsodanev2=
[email protected]> wrote:

I got it from an auction site called nellis auctions. They sell surplus
amazon merch.
I have called them and they are will to return my $$ upon return of
defective unit. But cannot exchange it for a different one.

I got it from an auction site called nellis auctions. They sell surplus amazon merch.
I have called them and they are will to return my $$ upon return of defective unit. But cannot exchange it for a different one.

Thanks, looks like this is the only answer I got.
Where could I get a more definite answer? This should be mentioned somewhere, in a documentation or in gitlab. :/

I managed to get it work with v1.2.40 firmware from DiSlord and the DfuSe Demo software.
Initially I was using the wrong path to update the firmware, essentially uploading instead of updating, like in the photo. Rookie mistake.

Hello everyone!

I managed to brick my nanoVNA H (clone, as I've found later on this forum) and now it is showing a white screen.
First of all, I should have read this forum before the purchase and buy the real thing, but the product looked legit at the first glance.
Second, I should've made a copy of the initial firmware before I install the new one. But what is done is done and I'm looking forward for a posible solution.
Do you know what firmware came with this thing in the first place, to help me roll back? Since it is a sofware problem I imagine it can be done, but the seller didn't provided his support. Thank you!
There are some pictures with the front, back and inside the nanaVNA.

Yes, use ZeeTK, the new version firmware will perform an LCD clear during the boot process and the color stripes will disappear after boot.

You might start with stating where you got it from?

On Tue, 11 Mar 2025 at 02:19, alsodanev2 via groups.io <alsodanev2=
[email protected]> wrote:

So i have in front of me a brand new in package/container: a brand new -f
v2
All metal housing, protective plastic on screen.
Upon start. Turn on. Screen flashes white then goes dark.
Very faint lines and bars visible.
This is a brand new unit.
I am disinclined to take apart and mess with internals.

Should i return? Warranty?
How good is the company/manufacturer customer service?