开云体育

Still, the calibration is based on the value of the load used for calibrating.? If it's 51 Ohms you will have SWR of 1.02 with a 50 Ohm load.
However, this is usually a trivial error.
Bob

Wow, Dave! You got in the bus very late, didn’t you?

NONE of us are interested in this new QEX article for VNA theory! It’s about the empirical comparison of the NanoVNA versus other higher grade VNAs. Do you get that difference? I’ve got about a GB of books and articles (including the ones you’ve put links to instead of actually reading this thread) on VNA theory, tutorials, user & service manuals, etc.

Way back on Saturday Night Live, Emily Litella used to get in the bus late, too. But when she caught on, she exclaimed, Never mind!

What’s in your wallet? Lol

Yes, for that narrow range, you will have a set of cal values.The Nanovna natively scans 101 points and if you narrow the freq range, it will still scann 101 points in the narrow range so the interpolation between the points should be better than if the unit needed to interpolate using the 50k to 900M range over 101 points.?
Clear as mud?



On Sun, 22 Dec 2019 at 7:50 PM, Dave H<xwebsubs@...> wrote: Hello,

I'm new to VNA's and have just received my nanoVNA

All the YouTubes show calibrating from 50Khz to 900MHz

If you set the range to say 45MHz to 55Mhz, and then calibrate.

will it provide more accuracy over that range, than using the 50khz to 900MHz calibration.

Thanks.. :)

Yes, you need to place the choke in its position ON THE INTENDED AMPLIFIER chassis. In this manner the exact distributive affects of shunt C are properly noted.

And with all do respects to the VNA, I would much rather do this measurement with a GDO.

Or... convert your vna into the equivalent of a GDO by exciting the ch 0 port into a small link coil which would utilize the measurement system as a coupled transformer. Not unlike the GDO, coupling must be kept to a minimum so that reduction in Q affect of the choke under test is minimized.

Note, you will need to measure both the anti resonate as well series resonate points as you described. In the series mode, the choke is shorted. Again, a direct connect of this arrangement to ch 0 would seem problematic. Consider the vna system is placing 50 ohms in series with the choke under test!

I would encourage you to correlate the measurements with the vna and with the GDO technique before applying 4000 volts to that nice tube!

I would also consider if you have one... the classic chokes like the old National Radio R175 which had strong series resonate problems in the 15 meter band. They would burst into flames! See if the vna points out the alarm. You should be able to pick up both the series resonate and parallel resonate signature on the vna-Smith plot. I know the GDO does pick up these signatures and I have modified those chokes based on the GDO results to fix their problems.

Alan

Hello,

I'm new to VNA's and have just received my nanoVNA

All the YouTubes show calibrating from 50Khz to 900MHz

If you set the range to say 45MHz to 55Mhz, and then calibrate.

will it provide more accuracy over that range, than using the 50khz to 900MHz calibration.

Thanks.. :)

Actually a rather informative (and occasionally entertaining) thread.
No complaints here.
Good to know QEX may (will?) soon be electronically accessible to ARRL members,
one of the more compelling reasons to keep my membership going.

Jerry, KE7ER

I figured out how the Marker Span button works.?

You need to have TWO or more markers (M1-M4) enabled for the Span button to work.?

Essentially, when you press the Marker Span button, the last two ACTIVE markers will be used to set the frequency span to the current upper and lower marker freq values.??

It doesn't matter if you have 3 markers displayed. If the last two you moved were M2 and M3 and even if M2 is at a higher frequency than M3, the span will be set using the lowest and highest values of the 2 markers.?

I hope this helps with using the markers on the NanoVNA.?

Cheers and Holiday Wishes to All !
Larry. VE3LRI


On Sun, 22 Dec 2019 at 12:37 PM, Larry Rothman<nlroth@...> wrote: Hi Larry,
I can explain stop, start and centre but not span:

Essentially, these commands allow you to set the frequency range or span using the position of the active marker. Make sure the current onscreen frequency span is greater than what you actually require so you can use the marker settings to 'zoom-in'.

For simplicity, enable only one marker.

Now place (drag) the marker to the starting frequency of the range you want to investigate.? You can read the marker freq onscreen at the upper right area of the display as you move it.

Open the Marker menu and click the Start button and you will see the start freq at the lower left of the display change to the current marker freq.
Now move the marker to the maximum frequency of the range you're interested in and again, open the Marker menu and press the Stop button.

The upper frequency shown at the lower right of the display will now change to that value.? You now know how to set the start and stop frequencies using the marker menu.

To set the span, you will use the Center menu button.? You set the start freq as before but the second entry will be to move the marker to centre frequency you're interested in and press the Center menu button.? This will automatically adjust the start and stop frequencies to be equal, either side of of the center.

As for the Span button, it just turns green when pressed and does not seem to do anything. I will have to look at the source code to see what that's about.

I hope this helps. I will update the user guide with this information soon.

Regards
Larry

Here's a thought.? If you and others are so convinced that you have the moral high ground here, why don't you ask the author of the article for a summary via email (or a pdf scan like the other guy wants) instead of asking a third party to do so?

Dave?? AB7E

How about giving us the gist of his conclusion about it?
Basically a thumbs-up, thumbs-down, or just what he liked and what he didn't like. Don't do any quoting...put it in your own words.

Just a thought...

This link was posted on the NanoVNA Facebook group.

Very interesting tests of homebrew Male and Female SOL calibrators. He compared 1, 2 and 3 resistor loads.

Hi Terry, it's a long time ago.. Because the seach problems of the replaced LCD, i post the link for Ali. You must choose the version with touch. But it is in Dutch. Search the exact same LCD in your own language site by Ali.
,searchweb201602_6,searchweb201603_53

Can't we cease belly aching about *one article*? Agilent/Keysite has
excellent tutorials on the care and feeding of a vector network analyzer.
Just because it isn't the NANOVNA, the same theory applies.






And another very general treatment with nothing beyond simple high school
algebra:




All these, and others, are open, published, and available free of charge.
Open to education and learning on the www. Have at it and quit belly
aching over *one single article!*

Dave - W?LEV

On Sun, Dec 22, 2019 at 10:58 PM Frank Howell <frankmhowell@...>
wrote:

Andy,

Agreed! Even copying and pasting the Abstract with this info is fair use
as publishers frequently made titles and abstracts publicly available.

Personally, I’ve sent folks PDFs of articles they stated they would like
to read because they are actively studying the topic. This IS fair use,
just as going to a library and photocopying an article out of a print
magazine or journal is. Ask any professional librarian!

In my case, I have an active paper with two local E.E.s comparing several
NanoVNA devices with the MiniVNA, the Tom Baier VNA from Sdr-Kits, an
Agilent FieldFox, and a high end R&S VNA with precision loads and several
commodity DUTs that ham operators would often use. We will complete the
measurement schedule after the Holidays but will have to see if we offer
anything beyond this new QEX article.

It’s completely legal and ethically being a colleague if someone on this
list sends me either images of the article pages or a scanned PDF if that’s
easier. I’m good on QRZed and my email is here, too.

73,

Frank
K4FMH

--

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

Andy,

Agreed! Even copying and pasting the Abstract with this info is fair use as publishers frequently made titles and abstracts publicly available.

Personally, I’ve sent folks PDFs of articles they stated they would like to read because they are actively studying the topic. This IS fair use, just as going to a library and photocopying an article out of a print magazine or journal is. Ask any professional librarian!

In my case, I have an active paper with two local E.E.s comparing several NanoVNA devices with the MiniVNA, the Tom Baier VNA from Sdr-Kits, an Agilent FieldFox, and a high end R&S VNA with precision loads and several commodity DUTs that ham operators would often use. We will complete the measurement schedule after the Holidays but will have to see if we offer anything beyond this new QEX article.

It’s completely legal and ethically being a colleague if someone on this list sends me either images of the article pages or a scanned PDF if that’s easier. I’m good on QRZed and my email is here, too.

73,

Frank
K4FMH

OK,

I am a buyer. just tell me where to send the money!


Le ven. 20 déc. 2019 à 16:58, Martin via Groups.Io
<martin_ehrenfried@...> a écrit :

/g/nanovna-users/message/3872
--
Regards,

Martin - G8JNJ

You don't need a test jig to measure plate chokes.

They are influenced by the layout in the amplifier.

You need to measure the choke in it's operating position.

--Shane
KD6VXI

Thanks Larry, I didn't get that from the manual but sounds good.
Thanks
Larry
n0sa

#90.03: A Note on [SAMoEEiVNAM] Programming

In the usual case of the Triplet of Standard Nominal Value (-1, 0, +1), it may be
proved that it is programmatically advantageous to use different formulas for
the computation of G and Gt, that is of G_mini and of complete G, respectively:




#53 : Upgrade : The [LeastVNA]
17 October 2019 - /g/nanovna-users/message/5110

#88 : the G formula - our research work has been completed
21 December 2109 - /g/nanovna-users/message/8459

Sincerely,

gin&pez@arg

:#90.03

Thanks for all the replies. I have a box of chokes that I will set up and sweep. The plan is to build a test jig which will be a square tube with about 33mm of clearance on each side. This will ensure repeatability. I have been struggling to wind a good plate choke that covers all the ham bands including the warc bands. I just wanted to be sure that i was not wasting wire and using the wrong technique.

Henry

Bob,
thank you for clarification. I have measured a coil in this way( connected
only to CH0). Attached Smith chart and R, X graph.
The resonance can be seen easily around 12 MHz. However, in my case it is a
parallel resonance, impedance is very high.
For the plate choke we need the series resonance[s] which can cause serious
trouble in tube PA.

My question was not about the method, but about the accuracy.
Is the stray capacitance of the NanoVNA shifting the self resonance
frequency of the coil ?

73 Ady

[image: Coil - Smith.png]
[image: Coil - R & X.png]


On Sun, Dec 22, 2019 at 7:53 PM Bob Albert via Groups.Io <bob91343=
[email protected]> wrote:

The resonance of a choke is measured by connecting it to the S0 port.
You select Smith chart and, with the frequency at a low value you read the
inductance on the screen, with the plot being a dot at the left edge.
(First you select S0 reflection mode.)
Then you sweep the frequency up until the chart becomes a circle. The
point where it passes halfway around, to the right edge, is the resonant
frequency. You carefully adjust the frequency until the inductance reading
on screen switches to capacitance. That's resonance.
Bob K6DDX
On Sunday, December 22, 2019, 08:00:43 AM PST, Ady, YO2NAA <
yo2naa@...> wrote:

Will the reactance of NanoVNA's channels influence the resonant
frequencies of the choke, or the calibration process is removing this
influence?
If the influence is present, what method will minimize it the most?
Should the choke be measured mounted in the PA, to include the influence of
the neighboring objects?

73 Ady YO2NAA

On Sun, Dec 22, 2019 at 2:34 PM Jim Potter <jpotter@...> wrote:

To find a series resonance you are looking for the frequency where the
impedance is a minimum.
All three techniques you suggest will work.
1. Series between two ports, look for the frequency of maximum S21
2. Shunt, you only need 1 port. Look for the frequency of a dip in S11.
Don't connect Port 2
3. With two coupling coils the result will be like #1, The frequency for
maximum S21 is the self resonance
4. With one coupling loop the series resonance will be the minimum in

S11,

like #2. This is pretty much what you are doing with the grid dip meter,
looking for maximum energy absorption,

Try all of these techniques to see the difference. That's one of the

great

thing about the nanoVNA it's a great educational tool at an affordable
price.

73 de K9GXC, Jim

Hi,
I have not used the latest versions, so I could be wrong, but the way I
remember it, is that you have to run a manual scan before you use the
buttons.
So, leave the port open, run a scan, press the open button, connect the
short, run a scan, press tbe short button, connect the load, run a scan,
press the load button, then apply the cal.

Askild