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Many thanks to Eric for clarifying how the spectrum of the processed signal can be obtained.

So, NanoVNA outputs signal, and mixes it with a signal with an offset of XXX Hz (IF freq), all this goes to the SA612 mixer. From where the intermediate frequency goes to the ADC.

There the signal is digitized, and at the output we get I/Q samples
Further, there is the mathematics how to extract the amplitude and phase of the IF signal, compare it with the reference.
Well, according to this information, take everything further ... (apply calibration, made calculation)
I needed to understand how the ADC works qualitatively, which intermediate frequencies are better or worse. What is the noise level.
Now, thanks to Eric's help, you can see it visually. And make changes to the settings on the fly and see the result.

So, in the end:

Attached screenshots for ADC 384k (full screen data)
1 screenshot offset 50k
2 screensot offset 98k
3 screenshot offset 196k

You can see clean data, some offset harmonics, in futuire i try made more screenhots for show how it work on higher frequency, noise level and so

Sorry to appear dim (retired doctor with electronics interest), but I could not find any reference to Eric’s clarification, so I am at a loss to understand what is going on, with the interesting screenshots at the end of the message.

I would be very interested if the nano could be used as an occasional spectrum analyser, especially with small resolution bandwidths, so I will try to “keep up” if there are any more posts to this subject.

Steve L. G7PSZ

nanoVNA use IF for measure data (CH0 reference, reflection, and CH1)

Default not allow see how it work.

I add some code from Eric SA-FFT sources, and can better see ADC work quality (screenshots)

This feature not added in NanoVNA (and i think not need)

The only reason to add the FFT code/mode would be to allow the use of a nanoVNA as a narrow band spectrum analyzer using the CH1 input with the disclaimer there is NO mirror suppression so interpreting what you see can be VERY difficult.

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

Isn't someone in the group working on a SA/TG project for the Nano?

On Fri, Aug 7, 2020 at 01:07 PM, <lobos305@...> wrote:

Isn't someone in the group working on a SA/TG project for the Nano?
========================================
A SA/TG provides pretty much the same functionality as an s21 measurement on the NanoVNA - without the additional phase information. As Erik pointed out in an earlier post, and loosely quoted by me :

"Adding a FFT code/mode would allow the use of a nanoVNA as a narrow band spectrum analyzer using the CH1 input with the disclaimer there is NO mirror suppression so interpreting what you see can be VERY difficult"

I try to keep up with new NanoVNA developments and as far I know there are no combined NanoVNA/spectrum analyzer projects in the works. Owning a NanoVNA and tinySA comes very close to what you want, albeit in separate packages, at total cost of around $100 for both.

- Herb

It would require an external mixer, and external 2nd LO, and some amps.l
I suggest the

The dim doctor again, here. I think I understand a bit better now.

Might I suggest that the fft code added could produce a very useful narrow band spectrum analyser feature to the Nano, with a narrower minimum resolution bandwidth than the Tinysa.

Yes there might be odd spurs which would have to be sorted out by the operator, perhaps by a tiny frequency change of the signal being examined, or a nudge to the centre frequency of the Nano. But that is half the fun for us hobbyists, especially if one has access to resolution bandwiths otherwise only available on very expensive kit, or cobbling up a sdr dongle into a compurer somehow ( I have managed to display “apparent” resolution bandwidths of 10hz using a rsp1 sdr box - I do not know if it was real, but it looked impressive on the computer screen).

At ?50, special firmware on a dedicated extra Nano (I already have two) just for very narrow rbw would be worth having. I presume the minimum useful rbw would be limited by the device’s phase noise of the various oscillators.

Steve L. G7PSZ

Simple SA in ADC range 192k (-96k to +96k) around Center frequency
(Offset frequency disabled for measure input)
Connect generator to CH1 input and set 30.050MHz output

On nanoVNA set:
Center freq 30MHz
Span 192k (it just for markers)
Disable all traces except 1
Format Logmag
Ref level 0
Scale 15

No mirror suppresion!! No level calibration!!
Just for Proof of Concept

For persinal use (no any sources):

Also work command promt gain command for apply ADC internal amplifier gain from 0 to 95
For example set 50dB gain
'gain 50'

DiSlord-А прошивку для Н можно попросить?

Попросить можно, но не сдесь!:)

If you're looking for an inexpensive wideband spectrum analyzer, the
tinySA project may have what you are looking for.

For narrowband spectrum analysis, it's hard to beat a good SDR receiver.
The spectrum display will show you what you're looking for, with excellent
resolution.

On 8/8/20 11:16 AM, Shirley Dulcey KE1L wrote:

If you're looking for an inexpensive wideband spectrum analyzer, the
tinySA project may have what you are looking for.
For narrowband spectrum analysis, it's hard to beat a good SDR receiver.
The spectrum display will show you what you're looking for, with excellent
resolution.

generally true - I find my RTL-SDR a pretty handy little widget. And, I've done a LOT of work in the last few years with 4GHz SignalHound. However, there are times when the $20k Keysight FieldFox is the thing to have.


what inexpensive(<$100) analyzers don't give you:
1) front end tracking filter and good image rejection
2) front end attenuator with a fair number of steps (helpful to know if you're seeing IMD in the analyzers front end, among other things)
3) stability over time

What medium priced USB analyzers ($1000-2000) give you:
filters, attenuators, wide bandwidth (DC-12 GHz)


Most of those mid priced Spectrum Analyzers are basically a specialized SDR - a tunable down converter/digitizer with attenuators and filters, and some software on the back end to do all the features. Generally better stability and aging, too.

One other thing that "real lab gear" gives you is a lack of radiated emissions. The USRP, for instance, is a very popular device, but also radiates a significant amount of the Local Oscillator from the input cards. So that requires some care to "do it right" rather just slapping together some gnuradio blocks.

On Sat, Aug 8, 2020 at 04:29 PM, Jim Lux wrote:

1) front end tracking filter and good image rejection
2) front end attenuator with a fair number of steps (helpful to know if you're
seeing IMD in the analyzers front end, among other things)
3) stability over time

How does the tinySA compare to these requirements?
--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

Dear Shirley,

Thankyou, I have been very busy and displaced from my electronics den for a year, but it is nice to know that what I saw using rtlsdr recievers was actually genuine narrowband signals. My search for such a facility can therefore end. Its only disadvantage is the pc attached to the sdr dongle and the lack of reliable amplitude calibration.

I am still waiting for Tinysa to arrive and looking forward to using it, especially for tracing hf interference which I suspect is caused by the data ( internet, tv channels etc) down the telephone wires.

The days of my HP and other boatanchor equipment are now diminishing.

Steve L. G7PSZ