I received the RF Demo kit for NanoVNA. The cables are indeed fiddly to attach on the pcb board, but I am getting used to it. Just hope that it will last for some long time rather than get mangled, and ruin my investment for the learning.

Anyhow I got it to calibrate OK for Open, Short and Load with the Demo Kit board and supplied cables.

But when I tried to read for the 30Mhz Band Pass Filter, the readings on the screen didn't come out what is indicated on the board. It was more squiggly curve type graphs on the display. I tried to change the settings with the SPAN and SCALE in the menu, but it made it actually worse or was just showing straight horizontal line.

Could someone please explain, what settings the VNA must have to display nice sharp dip of the graph as on the board? What am I doing wrong. I understand the RF board is showing how the band pass filter on the board is blocking the all other frequencies and only letting in 30Mhz in the filter? What should be the settings in the menu of the VNA? Thanks

Greetings, The open, Short, Load calibration is fine for single port measurement. However, there are two additional calibrations to be completed when you intend to perform two port measurements. There is the isolation which is sometimes done just leaving both ports open.I have also seen where it is suggested to put 50 ohm calibration loads on both s11 and s21(if you have them). Last is Thru (you probably have that on your test board) If not, you can just use a jumper from S11 to S21 for the calibration. This is my two cents worth, others may wish to comment further.Good Luck73

On 2/5/23 12:36 PM, PDXer wrote:

I received the RF Demo kit for NanoVNA. The cables are indeed fiddly to attach on the pcb board, but I am getting used to it. Just hope that it will last for some long time rather than get mangled, and ruin my investment for the learning.
Anyhow I got it to calibrate OK for Open, Short and Load with the Demo Kit board and supplied cables.
But when I tried to read for the 30Mhz Band Pass Filter, the readings on the screen didn't come out what is indicated on the board. It was more squiggly curve type graphs on the display. I tried to change the settings with the SPAN and SCALE in the menu, but it made it actually worse or was just showing straight horizontal line.
Could someone please explain, what settings the VNA must have to display nice sharp dip of the graph as on the board?

That would likely be the S11 magnitude - in the passband, the filter lets the RF through, so it sees the 50 ohms on the other side, so reflected power is small (i.e. good match). Outside the passband, the filter probably reflects the power back, so S11 is close to 1.

S21 should show the bandpass characteristic (i.e. small magnitude (large negative dB) outside the passband and big magnitude (small negative dB)) inside the passband.

That would likely be the S11 magnitude - in the passband, the filter
lets the RF through, so it sees the 50 ohms on the other side, so
reflected power is small (i.e. good match). Outside the passband, the
filter probably reflects the power back, so S11 is close to 1.

S21 should show the bandpass characteristic (i.e. small magnitude (large
negative dB) outside the passband and big magnitude (small negative dB))
inside the passband.

Do you set the frequency range say from 20 Mhz to 50 Mhz, and set the centre frequency to 30 Mhz, and then sweep the frequency to get the graph?
What about SPAN and RBW (band width) - what do you set it to?
And it is set to read LOGMAG of S21?
What is supposed to happen on S11?

On 2/6/23 9:26 AM, PDXer wrote:

That would likely be the S11 magnitude - in the passband, the filter
lets the RF through, so it sees the 50 ohms on the other side, so
reflected power is small (i.e. good match). Outside the passband, the
filter probably reflects the power back, so S11 is close to 1.

S21 should show the bandpass characteristic (i.e. small magnitude (large
negative dB) outside the passband and big magnitude (small negative dB))
inside the passband.

Do you set the frequency range say from 20 Mhz to 50 Mhz, and set the centre frequency to 30 Mhz, and then sweep the frequency to get the graph?
What about SPAN and RBW (band width) - what do you set it to?
And it is set to read LOGMAG of S21?
What is supposed to happen on S11?

I couldn't find a schematic for the test board, so I don't know what the BPF looks like.

Span is just the size of the sweep - either you set start and stop, or set center and span.

RBW leave at the default - it doesn't make any difference.

What I'd expect on logmag S21 is that you see the bandpass characteristic of the filter.
What I'd expect on logmag S11 is that you see the input return loss, typically sort of the inverse of the bandpass, but often, you can see the individual sections of the filter.

If I can find a schematic, I can simulate it.

If you're using Windows, you might try getting a copy of Elsie from Tonne Software. The student version is free, and it lets you build filters of various kinds, either from specs, or by knowing the component values, and it can give you plots of S21 and S11 (and lots of others)).

Elsie and a VNA is a great pair. You can design in Elsie, build the filter on a board, then sweep it with the VNA.

If you want real fun (?) you can build a 3 section LC filter with variable L or C, and use the VNA to tune it. (which is more art than science, btw) It's a LOT easier than, say, tuning the cans on a diplexer, because your run of the mill LC will have lower Q.

On 2/6/23 9:26 AM, PDXer wrote:

That would likely be the S11 magnitude - in the passband, the filter
lets the RF through, so it sees the 50 ohms on the other side, so
reflected power is small (i.e. good match). Outside the passband, the
filter probably reflects the power back, so S11 is close to 1.

S21 should show the bandpass characteristic (i.e. small magnitude (large
negative dB) outside the passband and big magnitude (small negative dB))
inside the passband.

Do you set the frequency range say from 20 Mhz to 50 Mhz, and set the centre frequency to 30 Mhz, and then sweep the frequency to get the graph?
What about SPAN and RBW (band width) - what do you set it to?
And it is set to read LOGMAG of S21?
What is supposed to happen on S11?

It occurs to me (after looking at some pictures of the test board)) that they might have just put something like a 10.7 MHz IF filter on the board.

Here's an example of such a filter, from Minicircuits.com

https://www.minicircuits.com/pdfs/BBP-10.7+.pdf

https://www.minicircuits.com/pages/s-params/BBP-10.7+_GRAPHS.pdf
the first plot is S21, the second is S11

here's another one:
https://www.minicircuits.com/WebStore/dashboard.html?model=BBP-35B%2B

https://www.minicircuits.com/pages/s-params/BBP-35B+_GRAPHS.pdf

The boards use three terminal ceramic filters for Bandpass. (Really only two terminal, but can be installed without regard to “polarity”.

They are actually ceramic resonators and sell for about 10-15 cents apiece from China.

Since the evaluation boards have been sold for as low as $8.00, the manufacturers will use low cost components.

Larry
AC9OX

On 2/6/23 10:14 AM, Larry McElhiney via groups.io wrote:

The boards use three terminal ceramic filters for Bandpass. (Really only two terminal, but can be installed without regard to “polarity”.
They are actually ceramic resonators and sell for about 10-15 cents apiece from China.
Since the evaluation boards have been sold for as low as $8.00, the manufacturers will use low cost components.

Anyone have a part number? Usually, the data sheet will show S21 and S11.

This is what I got.

I can tell it was wrong setting. It is showing resistance?
I should have set it for LOGMAG?
Will try again later.

Set it to LOGMAG.
Freq. range was 1 - 100 Mhz.

On Mon, Feb 6, 2023 at 12:37 PM, Jim Lux wrote:

Elsie from Tonne Software

Is there a 64 bit version?

Thanks, larry

On 2/7/23 1:37 AM, PDXer wrote:

This is what I got.

Well, it sure looks like a low pass filter - the cutoff looks a bit high for a filter described as a 30 MHz Low Pass. I'd set the span to something like 0.1 to 100.1 (that makes the divisions on the screen an even 10 MHz), so you can see well below the cutoff.

What's the vertical scale set to? 10dB/div?

I'd take a look with the reference level (top line of display) set to 0 dB, and something like 2 dB/div 5 dB/div, so you can see the "top of the passband". Depending on the filter, there may be some ripples, or, alternately it will be the passband loss, and then gradually rolling ddown.

On 2/7/23 1:41 AM, PDXer wrote:

I can tell it was wrong setting. It is showing resistance?
I should have set it for LOGMAG?
Will try again later.

Definitely Log mag is what you want.

On 2/7/23 3:40 AM, PDXer wrote:

Set it to LOGMAG.
Freq. range was 1 - 100 Mhz.

That's more like it, although it sure doesn't look like a *30 MHz* LPF. More like 10 MHz. You might zoom in on 1-21 MHz.

OTOH those ceramic filters are not necessarily 50 ohms in and out,

Try the BPF.

On 2/7/23 5:20 AM, Lawrance A. Schneider wrote:

On Mon, Feb 6, 2023 at 12:37 PM, Jim Lux wrote:

Elsie from Tonne Software

Is there a 64 bit version?
Thanks, larry

i don't think so, but it runs fine on my Win 10 64 bit machine.
It also runs in parallels on Mac OSX, Win 10 64 bit R85

I managed to get the hang with it, and carried on with the next few demo practices.
The key thing to make it look similar to what the board is showing was, to manipulate with the frequency settings, by tracing the line with the marker reading what it is saying. And then resetting the frequency either to extend or shorten the line made the displaying graph similar to the ones on the board.

Many thanks for your info and advice on this.

On Tue, Feb 7, 2023 at 08:58 AM, Jim Lux wrote:

It also runs in parallels on Mac OSX, Win 10 64 bit R85

What is "R85"? And thank you for your reply!! larry

On 2/8/23 5:30 AM, Lawrance A. Schneider wrote:

On Tue, Feb 7, 2023 at 08:58 AM, Jim Lux wrote:

It also runs in parallels on Mac OSX, Win 10 64 bit R85

What is "R85"? And thank you for your reply!! larry

I think it's "release 85"
it's on the splash screen when it starts up.

It might be something in the Windows image that Parallels uses

I had a hard time determining if the Demo RF Kit was the same as offered by Amazon and other vendors. I think the person who initiated the Post should have first taken a picture of the RF Demo Kit to show the uninitiated first what is being discussed, then go into the how, why ETC. now that I understand what is being talked about I am very interested.
I just received my nanoVNA -F v2 and I expect delivery of the RF Demo Kit on Monday Dec 30
To me this is an obvious place to start. I am not interest in going out side at -20 C to attach my antenna just to begin learning how to use the nanoVNA device.
Thanks to PDXer for posting the picture of the "Frequency Test Board RF Demo Kit VNA RF Test Module Vector Network Analyzer Breadboard Test Protoboard Board"