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On Fri, 20 Sep 2019 at 00:12, hwalker <herbwalker2476@...> wrote:

All my low noise RF preamps have a maximum input of 0 dbm and can handle
the maximum output power of the nanoVNA without an attenuator.

Whilst an LNA can probably take 0 dBm without damage, it would be driven
well beyond its linear region.

I just took as quick example, one of the Minicircuit amplifiers I have here



1 dB compression point +5 dBm
Gain > 24 dB

That means a signal of 5-24 = -19 dBm would drive that into compression. A
typical amateur radio LNA would almost certainly have a 1 dB compression
point of < 0 dBm.

I reckon something around a 10 dB attenuator on the output of port 0 would
be desirable before an LNA, and another 20 dB or so after the amplifier.

A typical amateur LNA would use a FET. The largest 1 dB compression point
would be achieved with a high drain current and lowest noise at a smaller
drain current.


Dave

Dave.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

Kurt,
After your comment about not being impressed with the HP 50 ohm loads, I checked their return loss from 50k-900MHz and you are correct that their high frequency return loss is not impressive. At 50 kHz the return loss is a respectable 37 dB but it gradually rises to an unimpressive 24 dB at 900 MHz. I got suckered in by the HP name and did not verify performance. The HP terminators have been kicked out of my OSL kit and replaced with JFW loads that have a minimum return loss of 35 dB at 900 MHz. Thanks for the tip.

All my low noise RF preamps have a maximum input of 0 dbm and can handle the maximum output power of the nanoVNA without an attenuator. You have to know what your system budget is and choose your attenuators accordingly. I always look up the specs for the maximum gain and maximum input power of the amplifier under test prior to testing. As an example, today I tested an HP8447D RF preamp. It has a specified 25 dB gain from 100k-1.3GHz and a maximum input of 0 dBm. Knowing those facts, I chose to use at least 25 dB of attenuation in-line during testing to offset the gain of the HP8447D, and stay within the 40 db S21 dynamic range of the nanoVNA at 900 MHz. If you are testing below 300 MHz you can get away with a lot more attention in-line (S21 dynamic range is spec'd at 70 dB). I ended up using a 10 dB and 20 dB attenuator in-line. The 10 dB attenuator was connected to the CH0 output of the nanoVNA and the input of the HP447D. The HP8447D can handle the output of the nanoVNA without an attenuator, but it is good practice to use an attenuator to lower the mismatch and provide isolation. The 20 dB attenuator was connected to the output of the preamplifier and the CH1 input of the nanoVNA . As with the other RF preamps I've tested using the same procedure, the system operated linearly over the 50k-900 MHz test range and the measured gain of the HP8447D was 26 dB =/- 1 dB. This result was verified using a calibrated HP8753C VNA.

The above is my typical S21 measurement procedure for verifying the gain of a low noise RF preamp, such as one that might be used to improve the noise floor of a receiver or spectrum analyzer. When testing a block LNA more attenuation, as suggested by qrp.ddc, may be in order.

On Thu, 19 Sep 2019 at 17:19, Said via Groups.Io <cn8li@...>
wrote:

Hi hwalker.Very thanks for answering my post & i read before your
procedure. So the S11 isn't interesting in the LNA Performance.
Regards.

From all four S-parameters it is possible to work out the Rollett
Stability Factor K



which will allow you to determine if the amplifier is unconditionally
stable. So to say S11 is no use is incorrect.

On a professional VNA you can add an attenuator up to about 20 dB on a port
and perform a 1-port calibration. 20 dB is about the limit. I don’t know
what you might get away with using the NanoVNA.

Dave.

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

Yeah, sorry about the window link, I was half asleep at the time.
DMR has mentioned a Linux how-to in this thread.

/g/nanovna-users/topic/33072199#1507
I think it's about the 4th post in.

It mentions using cygwin on windows but you'll get the gist of it.
Search for posts by forum member Lapo as he also is building in a Linux environment.

Cheers
Larry

If you are modifying the FW *please* maintain a file in the Firmware folder with release notes and version information along with the location of the source repository.

If you make comments such as "TDR is now in the FW" *please* state which version. This has turned into an Abbott and Costello skit.

I had asked about a post about instructions for building the FW on *Linux*, not Windows. The search feature doesn't produce anything useful. The maddening part is I'm pretty sure I thanked the person who did that, but I cannot even find a list of my own posts.

I've downloaded both the ST development tools and the Gnu tools onto a Debian 9.3 system, but I'm now so confused about who has done what that I'm reluctant to actually do *anything*. I don't want to reinvent the wheel. and unsure about whether the version that came on my unit is buggy and needs fixing to use the command line console.

I'd like to see if I can improve the dynamic range at higher frequencies with some DSP. Depending upon the nature of the situation, I think it might be possible to pick up 20-30 dB improvement.

But at the moment I'm completely befuddled by "Who's on First".

Also, if you're quoting and commenting inline *please* delimit the quotes from your own comments. There have been a number of posts I gave up trying to figure out. They looked as if there were 3 or more authors.

Reg

Aha. That's what are for. It works now, Thank you.

Today I received my third Nanovna. This one, I believe, is one of the "better" quality, completing the triad of better, worse, worst. The construction is noticeably higher quality with full, soldered shields on both ports. It came packaged neatly in a plastic box but with no battery. The front and back covers are painted fiber board, the same as the "worst" white salamander and not like the aluminum covers on the "worse" black model.

After calibration at 50, 450, and 720 MHz one significant performance difference was noted. The noise floor in the S11 Logmag display was noticeably quieter at -64 dBc. It was perhaps 5 dB p-p as compared with about 15 dB p-p for the "Worse" and "Worst" models.

However, when testing it at normal measurement levels there was no significant difference in the measurements at any of the three frequencies among all three. A summary of test results for the three Nanovnas, an AAI VIA, and my Rigol SA/RFbridge combo is attached.

For my purposes the three different versions are substantially identical and I would not hesitate to use and recommend any of the three.

Warren Allgyer
WA8TOD

Hi,
check for the "Smith.png" and "Admittance.png" file.
They should be in the same direcory as the "NanoVNA.exe" File.
73 Harald
OE3HBS

The NanoVna seems to work but when I look at results on the PC screen I can't see the Smith chart. I see results plotted on the screen, probably on the Smith chart but Smith chart itself is not visible.
This is a Windoews 7 32 machine with a ordinary 27" inch screen. PC software gives this info(probably about the device): Kernel 4.00 Build time 2. Aug 2019.

Ok Larry, its a starting point that I never knew about.

I've not investigated anything to
do with the terminal stuff yet.

73 de Andy

Greetings Mr. QRP,

Thanks for the analysis! Gosh it is amazing how close my DIY 50 Ohm BNC load with adapter combination match the SMA 50 Ohm reference load that came with my nanoVNA! I don't know how good the supplied reference is in terms of return loss but at least it is comforting to find that the two loads match closely. Part of the reason for the good match may be because the SMA F-F adapter used to connect the supplied SMA load is roughly the same length as the BNC-SMA F-F adapter. Your VSWR plot shows that the VSWR buckets out around 200 MHz. Maybe by pure coincidence my SMA-BNC F-F adapter happens to add a tiny amount of series inductance that cancels some of the 0.5pF shunt capacitance exhibited by my DIY BNC load.
--
Enjoy!
Tom
VA7TA

Interesting!!

On Thu, Sep 19, 2019 at 03:17 PM, hwalker wrote:

and a 6 dB attenuator to CH0

6 dB is too small, the output level may be very high for LNA and may overload it, so you may get incorrect measurement. I'm using 30-60 dB attenuator on the LNA input for measurement.

Thanks. Just what I wanted.

Hi Nick,
please try putting the full path to the file in the field, not just the
file name. It may be a matter of which folder the software sees as its
working folder (generally controlled by your OS).

I liked the firmware message as well, but I haven't found a nice place to
put it, and several people were having problems running out of screen real
estate - so for now, it's no longer shown. I'd love to have it back, though.

--
Rune / 5Q5R

I agree and was going to put forth the same request as Rudi just did:

On Thu, Sep 19, 2019 at 02:39 PM, <reuterr@...> wrote:

Hello Erik,
Thank you for adding your extension to the Hugen nanoVNA version 0.1.1.

It would be nice to fill out in the "version window" the version number,
e.g.: 0.1.1 + scan, 1500MHz

Then you could look up what version is actual flashed.

Due to an ever-increasing number of NanoVNA firmware developers providing binaries on this forum (I think it's up to 5 now) and building different variations and/or experimental versions, I (and others) have a request to make of those same developers:

Please use the NanoVNA's boot-up central message field to provide at least the developer's forum name along with their version number (or date) and possibly included options.

All Nano F/W versions I download are archived and labeled with the developer name, date, F range and any other options along with any sub-version numbers if updates come out.
It could be automated through the make file for convenience.

How do the developers (you know who you are) feel about this?

73
Larry

Hi Rune

thank you so much for this application which I have been using to good effect this past week with the nanoVNA.

I think there may be a problem with saving and loading calibrations.

Yesterday I did a calibration which I called full_sweep. The full_sweep file was saved to the nanovna-saver directory, and I could shutdown nanovna-saver, restart it, and load the calibration.

Today it will not load. I get this

2019-09-19 19:49:53,703 - NanoVNASaver.Calibration - ERROR - Failed loading calibration data: [Errno 2] No such file or directory: 'full_sweep'
Traceback (most recent call last):
File "/home/nick/nanovna-saver/NanoVNASaver/Calibration.py", line 430, in loadCalibration
file = open(filename, "r")
FileNotFoundError: [Errno 2] No such file or directory: 'full_sweep'

The file is still present. Is this a problem with directory paths?

73
Nick
G3VNC

PS: I used to like the build date message from the firmware when you first connected to the device!

Hello Erik,
Thank you for adding your extension to the Hugen nanoVNA version 0.1.1.

It would be nice to fill out in the "version window" the version number,
e.g.: 0.1.1 + scan, 1500MHz

Then you could look up what version is actual flashed.

I am working mainly with MacOS.
In case you use the program "dfu-util" on Linux or MacOS for flashing, the USB vendor ID is 0000 in your .dfu file, and you cannot flash.
Error message: dfu-util: Error: File ID 0483:0000 does not match device (0483:df11 or 0483:df11)

In this case I have to transfer your .dfu file to Windows, use DfuFileMgr.exe to convert your file to .hex,
and convert it back to format .dfu with entering the USB vendor ID: DF11.
Then copy it back to MacOS and use dfu-util for flashing.

Therefore it would be also nice to add the USB vendor ID : DF11 to your .dfu file.

73, Rudi DL5FA

Some clarification from my earlier measurement.

The Measurement output from CH0 ranges from -13 dBm at 55 kHz to -36 dBm at 900 MHz..... a more than 23 dB variance.

Beginning at the first increment above 300 MHz the Measurement output switches from fundamental to 3rd harmonic. So, for example, when measuring at 330 MHz the 330 MHz Measurement output being used will be at -19 dBm the there will also be a much higher power fundamental signal output at 110 MHz at -9 dBm. The Nanovna ignores this fundamental frequency by virtue of its heterodyne mixing but users should be aware of its presence when performing S21 measurements of preamps and the like. These relatively high power fundamental frequencies can easily overload amplifiers and distort measurement results.

Another example: The Measurement output at 900 MHz is way down at -36 dBm but the 300 MHz fundamental that is generating that measurement frequency is also present at a whopping -9 dBm, nearly 30 dB higher! User beware!

Warren Allgyer