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#81" : update : on the physical expression of two-port s-parameters
REF: 9 December 2019 - /g/nanovna-users/message/8065
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#81' : update : on the physical expression of two-port s-parameters
8 December 2019 - /g/nanovna-users/message/8013
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Well, regarding o, O, 0, 1 and l appearance : after numerous trials-and-errors,
we dropped the use of [Liberation Mono] and use [Bitstream Vera Sans Mono],
[Bold], [16], [Release: 1.10]:

hi,
please release source code.
i use linux
I forgot virus and antivirus....

Stylus: Cheap plastic 0.5mm "Bic" mechanical pencil, with the lead withdrawn. It even has a nice rubber grip! As a bonus, you can pump the lead out 1 click and take notes! :)
73, --kv5r

Hi Rudi,

Copy everythimg from screenshot. I not lucky, i tried write longer reply from my phone. I lost it 3 times. I will help you if required from my pc.

73,
Lajos

HI Ed,

Have you tried downloading it from this link:


Kind regards,

neb

Hi betex,

Thanks for having interest with the software, I posted the latest version here:
/g/nanovna-users/topic/nanovnapartner_v0_17/67737499?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,67737499

And you can download it from this link:

Kind regards,

neb

Hi neb,

your software looks quite nice, but unfortunately the link has expired...

Could you please upload it again?

Many thanks!
betex

Many thanks for all your answers!

Taking now a 2m cable with ferrites at both ends is working really great!
No more signal-affecting when connecting to USB!! :-))

...and of course it might not be a correct design for a ground plane antenna, I think it is not bad at all...

betex

And check the connectors, not the markings on the cable. I have seen 75 ohm
coax jumpers with 50 ohm BNC connectors on the ends. Such cables are not
recommended if you are using a resonant antenna, but will be just fine if
you are using a non-resonant antenna with an antenna tuner.

On Mon, Dec 9, 2019 at 09:33 AM, QRP RX wrote:

"Just use menu STIMULUS and set STOP = 30 MHZ. After that perform calibration and save to memory cell 0. Thats it. Now it will works to max 30 MHz with no harmonics mode."
=============================================================================

As an addendum to QRP's post, take into consideration that even if operation is limited below 300 MHz where the harmonics mode is used, because the SI5351 does not produce a sinusoidal output - harmonics will still be present in the CH0 output.

Perhaps your biggest gain by limiting your frequency range will be increased frequency resolution because you are using the NanoVNA's 101available measurement points over a shorter frequency span.

- Herb

Just use menu STIMULUS and set STOP = 30 MHZ. After that perform calibration and save to memory cell 0. Thats it.
Now it will works to max 30 MHz with no harmonics mode.

@ Gary O'Neil, N3GO - 9 December 2019
/g/nanovna-users/message/8059

Dear Gary,

No, there is not only the numeral two. There are a lot of ones and small Ls.

But, could you wait a little, please? We will try to improve the appearance of
the text, by using Liberation Mono of appropriate size or whatever else font,
sometime later and we hope that we would finish after two or three hours, at
most.

Best regards,

gin&pez@arg

On Sun, Dec 8, 2019 at 10:46 PM, <pgc1682@...> wrote:

I loaded to Sim Smith Chart your s1p data file.

Hello pgc1682,

Thank you very much for your help with SimSmith.

Unfortunately I cannot follow your explanation.
I have loaded my data file nanoVNA_RG173-30cm_202_500MHz_Open.s1p
in SimSmith, see attached screen shot SimSmith_RG174-30cm_DL5FA.png

Could you please tell me step by step what to do, to achieve your result?

73, Rudi DL5FA

On Mon, 9 Dec 2019 at 07:56, <erik@...> wrote:

Kurt,

It appears (in my limited understanding) the poor matching to Z0 of CH1
(port 2) is the biggest reason why the T-check is not performing well on
the nanoVNA.

I would not say the matching is poor on port 2. I measured it using my HP
VNA. At least on the NanoVNA sample I have, the return loss on port 2 is
better than the specification on my HP 8720D VNA. I did post some data on
the NanoVNA Facebook group.

I was unable to measure the source match at port 1 well due to the power
coming out of port 1. I had set my HP VNA source power to -20 dBm in an
effort to not cause any non-linearities. Testing at +10 dBm might have been
possible, but I don't know if the results could be trusted. Certainly
switching the NanoVNA off showed excellent match on port 1, and on port 2
is was quite reasonable, and largely independent of whether the unit was
powered on or not.

Erik, PD0EK

Dave

Why not just calibrate for the frequencies you care about and save as your
default?
It doesn't seem like a custom firmware is needed to only see a segment you
want. Since it is less than 300mhz, you would not be using harmonics,
anyway.

Just my opinion.

Marco

Hi Erik
Fantastic ... I did not know you was maintaining TAPR VNA (or I had forgotten it)
Looking forward to follow your project.

My transfer switch is also Sivers Lab but only PM7551 ? with a small control PCB with 5V to 28DC converter.
It went bust recently so now supplied by good old fashion AC/DC converter.
I did measure some WiFi channel filter with the VNWA successfully using a filter for the entire WiFi band to clean up the TX signal. That worked great. One og these days I will try it with the NanoVNA

Kind regards

Kurt







-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af erik@...
Sendt: 9. december 2019 14:30
Til: [email protected]
Emne: Re: [nanovna-users] The T-Check confusion



Hi Kurt.



Thanks. This is the switch I bought: SIVERS LAB PHILIPS COAXIAL SWITCH 28V DC-18Ghz PM7553 Isolation below 1GHz is better than 80dB so I guess below 300MHz good enough.

As I am currently the maintainer for the TAPR-VNA software so I can add whatever I want :-) Using the scikit-rf implementation as example I should be able to add (limited) 10/12 term calibration functionally to the TAPR-VNA SW, including controlling the transfer relay.



Lately I have been trying to optimize and tune various filters such as a 2GHz cavity filter and as I have to tune 5 resonators it would be nice if I did not need to reverse the DUT all the time as for best tuning you need to see S11,S21,S22 and S12 together. So it is more a matter of being kind to SMA cables and connectors and making tuning faster and easier.



For my home build VNA's I can also buy/build a second bridge, add a 4th receiver and put the transfer switch between the LO and the bridges. This will give me a fairly symmetrical setup allowing measurement of the errors in the bridge impedance. Disadvantage is the transfer switch is locked inside one VNA So many options to choose from, sounds like a hobby



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NanoVNA Wiki: </g/nanovna-users/wiki/home> /g/nanovna-users/wiki/home

NanoVNA Files: </g/nanovna-users/files> /g/nanovna-users/files

Erik, PD0EK

Two questions to answer:

1: Is there anything you can improve for HF by removing/adding it from the current firmware of the nanoVNA?
The only thing I can think of is to force the SI5351 to always use an even number in the final divider and thus reduce the spurs. As a consequence that scanning speed will be somewhat reduced. However these spurs have an neglectable impact so why bother?

2: Who will implement this?
That will depend on the first answer I guess

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

GIN&PEZ;

You are in excellent company. The Romans thought they could avert the zero issue altogether by not using it at all. They must have realized that the number 1 was going to be a problem when they ran out of fingers too. :-)

Is the number 2 the only numerical character used in your proof? I think I can differentiate the zero’s without ambiguity; I’m only uncertain of the ones and lower case L’s. Can I assume all are lower case L’s, and all as being measured Load values?

--
73

Gary, N3GO

The NanoVNA, and most VNA's in general, use the fact they know their transmitted excitation frequency and its harmonics to pick out the desired receive signal to simplify the circuitry.

The RF synthesizer generates two different frequencies separated by a few KHz's. One provides the transmitted test excitation frequency (along with its harmonics) and one provides the local oscillator for its mixer down conversions. The down conversion output is the difference frequency of a few KHz's. As a receiver this mixing will down convert based on difference of the Tx RF excitation and the mixer local oscillator frequency. There is no RF filtering for down conversion image rejection as it does not need it because it knows the expected Rx frequency. This is the first issue for using it as a general receiver.

It can pick out particular harmonics by adjusting the down converter mixer local oscillator frequency slightly relative to the Tx excitation frequency so the difference down conversion frequency is always in the same low (KHz) frequency range. The measurements of relative amplitude and phase are made at the low down converted frequency signal. The narrow bandwidth of the down conversion improves the ability to measurement of the desired signal but limits the use as a general receiver.

Software Defined Radio (SDR) receivers use a direct conversion mixer also known as zero intermediate frequency down conversion. It actually consists of two down conversion mixers that are given local oscillator signals that are exactly 90 degrees out of phase. This produces two outputs that are called 'I' channel ( In phase) and 'Q' channel (quadrature phase) signals that can be mathematically manipulated to recover all types of signal modulation methods. The I and Q channels are also known as baseband signals which are ADC digitized and are low pass filtered to half the desired RF receive bandwidth. The SDR method could be used for VNA measurements but it would be overkill complexity. Modern spectrum analyzers use this method and some also provide VNA capability within the same unit.

If there an improvement in significant performance, yes. However I expect it is a combo of hardware and firmware dedicated to HF that would be required to achieve that goal.

Alan