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Re: Help Testing a Low Pass Filter

M Garza
 

Have you tested the parts to make sure you have the correct values?

Marco

On Thu, Jun 4, 2020, 2:24 PM GM7 <geeemmseven@...> wrote:

Thanks Dave,

Your simulation is the response I expected. Unfortunately i's not the
response I'm measuring. I re-calibrated and then used the Smith Chart as a
sanity check. I got the expected results for open, short and 50 ohm load.

When I built the fixture I connected the ground permanently so that the
ground is connected between CH0 and CH1 even when the LPF is not in place.
I've re-tested without this link and got the same results. In general
terms I'm not sure if this link is a good idea or if I should remove the
link.
Re: NanoVNASaver Runtime Fault on Manjaro / Arch Linux #nanovna-saver #linux

 

Thanks for your response. I had seen that and other related questions on Stack Overflow. I tried some of the suggestions given, as mentioned in the original post.
Re: Help Testing a Low Pass Filter

 

Thanks Dave,

Your simulation is the response I expected. Unfortunately i's not the response I'm measuring. I re-calibrated and then used the Smith Chart as a sanity check. I got the expected results for open, short and 50 ohm load.

When I built the fixture I connected the ground permanently so that the ground is connected between CH0 and CH1 even when the LPF is not in place. I've re-tested without this link and got the same results. In general terms I'm not sure if this link is a good idea or if I should remove the link.

40m Response.png

white screen and flashing

 

After a full charge (usb connector led steady) , power it on, get white screen, with the led next to the power switch flashing. Ring a bell? Haven't found where in the users the flashing is mentioned yet. Sometimes it will start normally then go white at what seems like random timing.

Looks like lots of different flavors ....nanovna-XXX. Suggestion as to how can tell them all apart? and which one this is if can tell by peek, attached
rich

20200604_125417.jpg

Re: Help Testing a Low Pass Filter

 

I modeled your 40-Meter LPF using your values on ELSIE. Please see
attachment for the results of what you should measure for pass
characteristics (S21).

Dave - W?LEV

On Thu, Jun 4, 2020 at 12:05 PM GM7 <geeemmseven@...> wrote:

Hi, thanks for the replies.

It's a QRP Labs filter which uses the 7 element design shown in the
attached schematic.

I attached the wrong image in the first post. That's the response of the
40m filter, not the 30m (which was very similar). The values of the 40 m
filter are:

------ 1.3uH ------- 1.7uH ------- 1.3uH ------
| | | |
270pF 680pF 680pF 270pF
| | | |

I'll re-test the 40m filter following David's suggestions and post the
results.






--
*Dave - W?LEV*
*Just Let Darwin Work*

40-METER LPF for EMAIL - 04 JUNE 2020.jpg

Re: NanoVNASaver Runtime Fault on Manjaro / Arch Linux #nanovna-saver #linux

 

Has anyone had a similar issue
yes:

Re: Help Testing a Low Pass Filter

 

Hi, thanks for the replies.

It's a QRP Labs filter which uses the 7 element design shown in the attached schematic.

I attached the wrong image in the first post. That's the response of the 40m filter, not the 30m (which was very similar). The values of the 40 m filter are:

------ 1.3uH ------- 1.7uH ------- 1.3uH ------
| | | |
270pF 680pF 680pF 270pF
| | | |

I'll re-test the 40m filter following David's suggestions and post the results.

schematic.png

Re: Help Testing a Low Pass Filter

 

Which schematic and values did you use? That amplitude curve is weird.

Also, VSWR is very high on marker 3 (30 m)

Jos¨¦, CO2JA

On 6/4/20, GM7 <geeemmseven@...> wrote:
Hi All,

I'm trying to test a set of Low Pass Filters for 40m, 30m, 20m & 10m. I'm
getting consistent results for each of them but not the results I expected.
I'm struggling to establish whether the problem is with the filters or with
my test setup / calibration or even with the NanoVNA.

I've repeated this with and without a test fixture and got essentially the
same results. I attach the test fixture (see photo) and then calibrate
(reset, followed by open, short, isolation, thru). I then check the smith
chart with short, open and 50ohm loads to sanity check the calibration.

The attached image shows the 30m LPF. It doesn't have the passband I would
expect or the roll-off I would expect. Instead it's almost a linear
roll-off over the range under test.

Can anyone help? For example by either correcting my test methodology or
offering any advice. Thanks in advance.
Re: Help Testing a Low Pass Filter

 

True. Something does not look right. Rather than running 3 through 50
MHz, try setting, calibrating, and measuring 5 through 20 MHz. Also,
before you measure, to check your cal., do a Smith chart of short, open,
load, AND through just for sanity of the cal.

Your S11 looks, 'maybe', OK, the rest doesn't look as you or I would
expect. Also, once the filter is in place for measurement, flex the cables
and all SMA connections to be sure they are tight. When on my last job in
Albuquerque before moving to N. Colorado, everything was SMA or Type N
connectors. I carried a 11/16 open end wrench on my key ring. Don't over
torque, but be sure they are all tight.

Dave - W?LEV

On Thu, Jun 4, 2020 at 11:18 AM GM7 <geeemmseven@...> wrote:

Hi All,

I'm trying to test a set of Low Pass Filters for 40m, 30m, 20m & 10m. I'm
getting consistent results for each of them but not the results I
expected. I'm struggling to establish whether the problem is with the
filters or with my test setup / calibration or even with the NanoVNA.

I've repeated this with and without a test fixture and got essentially the
same results. I attach the test fixture (see photo) and then calibrate
(reset, followed by open, short, isolation, thru). I then check the smith
chart with short, open and 50ohm loads to sanity check the calibration.

The attached image shows the 30m LPF. It doesn't have the passband I
would expect or the roll-off I would expect. Instead it's almost a linear
roll-off over the range under test.

Can anyone help? For example by either correcting my test methodology or
offering any advice. Thanks in advance.




--
*Dave - W?LEV*
*Just Let Darwin Work*
Help Testing a Low Pass Filter

 

Hi All,

I'm trying to test a set of Low Pass Filters for 40m, 30m, 20m & 10m. I'm getting consistent results for each of them but not the results I expected. I'm struggling to establish whether the problem is with the filters or with my test setup / calibration or even with the NanoVNA.

I've repeated this with and without a test fixture and got essentially the same results. I attach the test fixture (see photo) and then calibrate (reset, followed by open, short, isolation, thru). I then check the smith chart with short, open and 50ohm loads to sanity check the calibration.

The attached image shows the 30m LPF. It doesn't have the passband I would expect or the roll-off I would expect. Instead it's almost a linear roll-off over the range under test.

Can anyone help? For example by either correcting my test methodology or offering any advice. Thanks in advance.

2020-06-04 18_14_21-Window.png
2020-06-04 17_53_40-Window.png

Re: Review of S-A-A-2 #nanovna-v2

 

Dear Cliff,

Thank you, my biggest problem that i am new in linux enviroment, so far I developed under windows. I can try to understand your advice...

If I have results or new question then I will come back...
Best 73
Re: Review of S-A-A-2 #nanovna-v2

 

Kedves Gyula,

K?szi, megn¨¦zem...

Nagy 73, Zoli
NanoVNASaver Runtime Fault on Manjaro / Arch Linux #nanovna-saver #linux

 

Hi, all-

First off, I have seen the many threads related to PyQT5, and I do not believe that this is the problem. Additionally, since Arch / Manjaro Linux is a distribution with rolling updates, the default Python version is 3.8, so the problems created by Ubuntu using Python 3.6 doesn't seem to be relevant, either. I had been happily using the excellent NanoVNASaver on Manjaro Linux last year, and recently returned to the Nanovna after a period without use. Now, every time I initiate the connection between the program and the device, the program will instantly crash, giving the following trace:

Traceback (most recent call last):
File "/usr/lib/python3.8/site-packages/NanoVNASaver/NanoVNASaver.py", line 637, in serialButtonClick self.startSerial()
File "/usr/lib/python3.8/site-packages/NanoVNASaver/NanoVNASaver.py", line 656, in startSerial self.vna = VNA.getVNA(self, self.serial)
File "/usr/lib/python3.8/site-packages/NanoVNASaver/Hardware.py", line 46, in getVNA firmware = tmp_vna.readFirmware()
File "/usr/lib/python3.8/site-packages/NanoVNASaver/Hardware.py", line 111, in readFirmware data = self.serial.readline().decode('ascii')
UnicodeDecodeError: 'ascii' codec can't decode byte 0x97 in position 0: ordinal not in range(128)
Aborted (core dumped)

I thought about posting this on the GitHub repository, but it appears that there are a number of issues that are weeks old that the author has not responded to. I figured this would have a greater audience and a more timely response. Anyway, while I dabble in some basic Python scripting, decoding serial streams is beyond my knowledge unless we're talking C/C++. As a simple attempt at a workaround, I tried to replace every instance of 'ascii' in the *.py files to 'utf-8', which is the default in *nix OS's. No luck. My locale is properly set, and I've added the PYTHONIOENCODING="UTF-8" environment variable to my .bash_profile, exported it, sourced the file, etc. Nothing seems to help.

Has anyone had a similar issue, or is anyone successfully running the latest NanoVNASaver on Arch or Manjaro?

Cheers
Re: Installed an ST32F303 in my Ver 1 nanoVNA #hardware #firmware #bootloader #hack #mods

 

Thank you for the info, hugen.
If there is no 8MHz xtal - I assume I will see the "Unknown USB device on port xx" error?
Since I can push S/W to the unit using my ST-Link,? do you know the location of any of Ken's development binaries where he was able to get the F303 working with the 2.8" LCD? At least I can check that the Nano starts-up OK with that.
Thanks!

On Thursday, June 4, 2020, 10:08:25 a.m. EDT, Hugen <hugen@...> wrote:

Hello Larry, STM32F303 comes with a bootloader, but you must connect an external 8M crystal to use DFU mode. This is why the independent 8M crystal is used on the nanoVNA-H4 instead of the 8MHz clock from the si5351. Therefore, if there is no external 8M crystal, you must use the SWD interface or UART interface to install the firmware.

hugen
Re: Installed an ST32F303 in my Ver 1 nanoVNA #hardware #firmware #bootloader #hack #mods

 

Hello Larry, STM32F303 comes with a bootloader, but you must connect an external 8M crystal to use DFU mode. This is why the independent 8M crystal is used on the nanoVNA-H4 instead of the 8MHz clock from the si5351. Therefore, if there is no external 8M crystal, you must use the SWD interface or UART interface to install the firmware.

hugen
Installed an ST32F303 in my Ver 1 nanoVNA #hardware #firmware #bootloader #hack #mods

 

Ken/Hugen -

I just installed a new ST32F303 on to my original NanoVNA and it is not recognized by USB (Yes, I installed 1.5K pull-up on pin33) so I assume I need to install the DFU bootloader.

Where do I find the bootloader binary for the F303? I've looked all over.

I can install firmware successfully using my ST-link, so that is not an issue.

Did anyone create instructions for replacing the bootloader on the 'nano? I think that would be good trouble shooting info to have.

Finally, Ken - can you send me a working binary you had developed for using the F303 with the 2.8 inch display so I can verify everything works?

I ultimately want to write up a document on how to enhance the original 2.8" Nanovna with an F303 processor and maybe add an SD slot in the process.

Thanks
Larry
Re: NanoVNA V2

 

Link for case
Re: out of "Presentation on the NanoVNA for the raileigh Radio Society", Now: "False Return Loss Calculations"

 

Yep, this is exactly what I do in courses.
If you know what loss is, and know what is meant by return loss, reading a text with a plus or a minus is no real bother.

But if they have to write up something, they'd better use the right sign in the context. :-)

Arie PA3A

Op 3-6-2020 om 23:18 schreef Dana Whitlow:

But if you teach, please, please, teach that a passive load's return loss is a positive
number of dB, as it is the only one of the two practices that is logically consistent
with the meaning of the word "loss". Of course you should probably bring this whole
controversy to the attention of your students and warn them to take a close look at
numbers presented in papers etc to be sure what the author really means.
Re: out of "Presentation on the NanoVNA for the raileigh Radio Society", Now: "False Return Loss Calculations"

 

On your other aspect of return loss:

Hi Dana and all,

Yes, indeed at low frequencies lossy transmission lines can have a complex characteristic line impedance.
In that case even some 2.141 > Gamma1 > 1 is possible, as the Gamma1 formula, correct for lines, for lines will yield.

This was described already in the late sixties by Robert A. Chipman in
"Theroy and problems of Transmission Lines" as well as by others.
At a close look one will see, that anyway that is not the invention of a "perpetuum mobile".

For describing lumped element mismatch caused Gamma2, application of the Gamma1 formula, however, leads to false results.

On transmission lines (Title and contents of Chipman's book is limited to these) we have actual reflections and
thus the Gamma1 formula is correct.

In lumped element mismatch caused cases "reflections" do not occur and
accordingly the Gamma1 formula does'nt apply - though looking similar.

So:

Let's distinguish these two cases rather than use the ATIS (former ANSI)
type of false assumption, that these were all the same.

By distinguishing the two Gamma cases, we avoid just one (less known) reason of a number of different possible
pitfalls, all leading to false negative Return Loss on passive lumped element mismatch circuits.

73, Hans
DJ7BA


--Urspr¨¹ngliche Nachricht-----
Von: [email protected] <[email protected]> Im Auftrag von Dana Whitlow
Gesendet: Mittwoch, 3. Juni 2020 23:18
An: [email protected]
Betreff: Re: [nanovna-users] out of "Presentation on the NanoVNA for the raileigh Radio Society", Now: "False Return Loss Calculations"

Hello all,

What you do in your own shop (or ham shack) is of course your own business.

But if you teach, please, please, teach that a passive load's return loss is a positive number of dB, as it is the only one of the two practices that is logically consistent with the meaning of the word "loss". Of course you should probably bring this whole controversy to the attention of your students and warn them to take a close look at numbers presented in papers etc to be sure what the author really means.

Now on to another aspect of return loss. I tend to define the system impedance Zo as the impedance of transmission lines commonly used in the environment, and I
tend to assume that the line impedance is a pure real number. This assumption (or
"approximation" if you prefer) is excellent in normal RF applications, but falls apart rather badly at very low frequencies.

Now here's my quandary: Only a pure real load impedance can absorb all the power incident on it. So if one is dealing with a system Zo that is complex, it seems to me that there is no load impedance that results in zero reflected power back into the line.
Is this reasoning too simplistic? When I took the transmission lines course at UMich
in the late 1960's, this issue was not addressed and I was not yet sharp enough to think to ask.

Dana




--
Diese E-Mail wurde von Avast Antivirus-Software auf Viren gepr¨¹ft.
Re: Review of S-A-A-2 #nanovna-v2

 

The Makefile is trying to get the current head revision identifier from git - but you have the source code without a git checkout. You should find the git repository you want to work from and clone that. Or better yet, fork it to your own account and clone your fork, so you can send a pull request.

Either way, your clone will have a .git directory which will have the HEAD file.
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