Re: Adapting the LiteVNA for SAR?
All of this begs a simple question.
Use the NanoVNA as a Field Strength Meter.
Why - Just built a new antenna using the NanoVNA to adjust it to the operational Frequency and adjusted the impedance for a match now it would be nice to be able to have some form of active display of the radiated signal, without blowing up the front end the NanoVNA
While I cause a simple diode detector and a meter using the NanoVNA is another possible use.
Any suggestions on how or how not to do it.
Thanks
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Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
I forgot to mention that initially NanoVNA-App would not load the renormalized .s2p file. I had to manually change R 330 to R 50 in the # line to get it to load. Before I discovered this, I used to create the plot I posted. I'm going to leave the renormalized impedance in the file since it's correct. Maybe someone will modify NanoVNA-App to be more tolerant.
It would be neat if NanoVNA-App would do the renormalization itself from forward and reversed .s2p files or live measurements.
Brian
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Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
The plot compares S21 of the forward 50 ohm file with S21 after forward and reverse were renormalized to 330 ohms. Stopband details of the renormalized curve differ from your earlier curve using a transformer, but the passbands look similar. Thanks for all your help, Don. Also thanks to John Gord for explaining why renormalization works even with improper device loading, which I didn't expect.
Brian
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Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
Hi Brian,
Your wish is my command. See attached .s2p files for my ceramic filter with 10 pf load connected direct to NanoVNA-F ports tested forward and reverse connected.
Note: I set my NanoVNA Saver to 5 sweep segments to provide decent resolution and hope it's adequate for your needs.
Don
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Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
Don, how about measuring the filter with a 10 pF load using no impedance matching (50 ohm source and load). Reverse the filter, measure again, and post the two .s2p files. I'm curious what my program will show dozens of dB down where the resistive pads limit the dynamic range.
Brian
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Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
Hi Brian,
I repeated the tests but this time using resistive matching pads to provide 330 ohm impedance to both the input and output of the ceramic filter versus using my very broadband transformers that provided a lower impedance (approximately 280 ohms). I also repeated using 270 ohm series resistors for matching. Since we now are only looking at the upper part of the response curve the loss in measurement dynamic range using the two different resistor methods should not be a problem.
Much different looking response using the resistive matching versus the transformers.
I again tested with a 10 pf, 33 pf, and 68 pf cap output loads and my reference curve used no capacitor on the load side.
Just FYI,
Don
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An update, was able to update to Version 1.2 still not able to direct connect to any of the PC apps
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Re: Starting trouble for NanoVNA!
I will try that next time! 73 Jon, VU2JO On Mon, Feb 17, 2025 at 10:54?PM Barry Leonard KN4JRF via groups.io <w9jbl= [email protected]> wrote: I have the same problem. Nanovna-H, Firmware V. 1.2.40. Had it for
several years.
Also the menu seems to start by itself, and go into whatever setting it
feels like. Maybe case is interfering with the touch screen. sometimes I
can press lightly on case and the menu acts randomly.
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Re: Adapting the LiteVNA for SAR?
? Use S21 mode with an amplifier.
People have been using VNAs as radars for years.
The NanoVNA just makes it easier.
Dealing with the big first reflection is tricky. One way is to use a separate cancellation path that is adjusted to null the first reflection. ?That’s what we did for the FINDER victim detection radar.
FINDER: Radar for Locating Disaster Victims ( )
jpl.nasa.gov ( )
( )
toggle quoted message
Show quoted text
On Feb 17, 2025, at 08:51, KENT BRITAIN <WA5VJB@...> wrote:
? Hi Larry
I have worked on several GPR projects.? One is currently looking for land
mines in SE Asia.
A LOT of loss going though dirt.??? And a big impedance bump at the
air/dirt interface.
They really need much more power than the Nano puts out.?? And since the
same port is Tx and Rec, an amp will not be simple.????? But lots of neat
stuff down there.?? Kent
On Monday, February 17, 2025 at 10:17:28 AM CST, Larry Rothman via
groups.io <nlroth@...> wrote:
Folks,
Using the NanoVNA as a signal source for Ground Penetrating Radar (GPR)
was discussed a couple of years ago. Today on Hacker News, there is an
article about a home-built Synthetic Aperture Radar (SAR) unit using a
freq around 6GHz.
The article discusses theory and the problem of finding a suitable Rcv
A/D. The LiteVNA has the freq range, is capable of resolving nS time (to a
certain amount), can measure phase and is programmable.
The big issue is probably the switching time of the generator/reflection
ICs in the front-end of the LiteVNA. As for the A/D spec, would the
heterodyne method and DSP used be a limiting factor?
So - might it be feasible to make use of the LiteVNA in a simplified radar
setup using an external controller and appropriate antennas?
Could the TDR routines be adapted?
Could the LiteVNA be used with a TinSA-Ultra and a controller for
something?
Just thinking out of the box here. In my 60+ years of Tech, I have always
looked at repurposing stuff. So, instead of "not possible" answers, I
would rather hear what might need to be changed (electronics /software) to
achieve a minimal proof of concept. Thinking caps on....
... Larry
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Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
Thanks, Don. Your filter shows much more response variation with a capacitive load than the 230 kHz filter in the Murata curves. I don't think anyone adds capacitance on purpose. In the past I have used pots instead of fixed 330 ohm resistors and adjusted them for minimum detected audio distortion. Since I now have quite a few spare filters, these days I just swap in another one, trying both orientations for minimum distortion.
Before I wrote this program, I used to worry a lot more about audio distortion:
Brian
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Re: testing non-50 ohm filters was Re: [nanovna-users] NanoVNA port renormalization
Hi Brian,
I went ahead and tested the filter response using a 10 pF, 33 pF, and 68 pF load capacitor. Attached are 3 plots and the reference plot on each of the attached plots is when I'm not using a load capacitor.
It should be noted that the curves shown in the datasheets you attached have the left vertical axis identified as attenuation in dB. In reality it appears that axis has been normalized based on the peak of the response curve. In my attached plots I have not normalized the vertical axis so you can see what the true attenuation is through the filter.
Just FYI,
Don
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OS is Win 11 Pro
I've changed USB-A/usb-c cables that was the first issue. I connected my phone to this cable and saw data, I believe the cable I'm using can communicate with the NanoVNA. I'm not seeing the Port COM device connection from the NanoVNA.
I went through the STM32 Bootloader installation and the STM Device in DFU Mode is showing up under the USBC grayed out. Attempting to connect out of DFU Mode, returns an unknown USB Device message. So in either mode can not connect to the NanoVNA. Attempted to change the configuration connection, both Serial (Serial speed 3800) and USB.
Thank you for your feedback, Stan and Bernie!
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Re: The scroll button change the Start frequency
Hi DiSlord
Thank you very much , long press by touchscreen on M1 marker and all become OK , I discover the long press functions Now Hi Hi
Thanks again.
73's Nizar .
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Re: The scroll button change the Start frequency
You select Start frequency change from leveler (click on start frequency at bottom) START at bottom Click on M: xxxxx Hz at top for select marker move mode
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The scroll button change the Start frequency
Hi All
I have H4 + 1.2.40 , after some use without problems , i have a serious bug with the scroll button , it does no more change marker frequency but start frequency , is it normal ? may be i am missing some setting ??
73's Nizar
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Re: Adapting the LiteVNA for SAR?
Thanks, Kent. I'm more interested in using signals through air. The front-end of the LiteVNA was described here: /g/liteVNA/topic/99749985#msg1054I see I made a mistake in my 1st post. The liteVNA doesn't use a similar DSP to the nanoVNA but uses the uP's internal DSP and several switches. However, all the switches can be statically set: reflect=open, Rx/tx synth set to ADF4350, rcv & ecal connected to ports. Then control Tx & Rx from external controller.
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Re: Starting trouble for NanoVNA!
I have the same problem. Nanovna-H, Firmware V. 1.2.40. Had it for several years.
Also the menu seems to start by itself, and go into whatever setting it feels like. Maybe case is interfering with the touch screen. sometimes I can press lightly on case and the menu acts randomly.
|
Re: Adapting the LiteVNA for SAR?
Hi Larry
I have worked on several GPR projects.? One is currently looking for land mines in SE Asia.
A LOT of loss going though dirt.??? And a big impedance bump at the air/dirt interface.?
They really need much more power than the Nano puts out.?? And since the same port is Tx and Rec, an amp will not be simple.????? But lots of neat stuff down there.?? Kent
toggle quoted message
Show quoted text
On Monday, February 17, 2025 at 10:17:28 AM CST, Larry Rothman via groups.io <nlroth@...> wrote:
Folks,
Using the NanoVNA as a signal source for Ground Penetrating Radar (GPR) was discussed a couple of years ago. Today on Hacker News, there is an article about a home-built Synthetic Aperture Radar (SAR) unit using a freq around 6GHz.
The article discusses theory and the problem of finding a suitable Rcv A/D. The LiteVNA has the freq range, is capable of resolving nS time (to a certain amount), can measure phase and is programmable.
The big issue is probably the switching time of the generator/reflection ICs in the front-end of the LiteVNA. As for the A/D spec, would the heterodyne method and DSP used be a limiting factor?
So - might it be feasible to make use of the LiteVNA in a simplified radar setup using an external controller and appropriate antennas?
Could the TDR routines be adapted?
Could the LiteVNA be used with a TinSA-Ultra and a controller for something?
Just thinking out of the box here. In my 60+ years of Tech, I have always looked at repurposing stuff. So, instead of "not possible" answers, I would rather hear what might need to be changed (electronics /software) to achieve a minimal proof of concept. Thinking caps on....
... Larry
|
Adapting the LiteVNA for SAR?
Folks,
Using the NanoVNA as a signal source for Ground Penetrating Radar (GPR) was discussed a couple of years ago. Today on Hacker News, there is an article about a home-built Synthetic Aperture Radar (SAR) unit using a freq around 6GHz.
The article discusses theory and the problem of finding a suitable Rcv A/D. The LiteVNA has the freq range, is capable of resolving nS time (to a certain amount), can measure phase and is programmable.
The big issue is probably the switching time of the generator/reflection ICs in the front-end of the LiteVNA. As for the A/D spec, would the heterodyne method and DSP used be a limiting factor?
So - might it be feasible to make use of the LiteVNA in a simplified radar setup using an external controller and appropriate antennas?
Could the TDR routines be adapted?
Could the LiteVNA be used with a TinSA-Ultra and a controller for something?
Just thinking out of the box here. In my 60+ years of Tech, I have always looked at repurposing stuff. So, instead of "not possible" answers, I would rather hear what might need to be changed (electronics /software) to achieve a minimal proof of concept. Thinking caps on....
... Larry
|
Upgraded GOOZEEZOO 7in NanoVNA SV4401A
Has anyone used the SV4401A nanoVNA ?
Thinking of getting one off Amazon, but most of the reviews are for other
models of nanoVNA.
Orrin WN1Z
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VE6LX
Roger C
Barry Leonard KN4JRF