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looks like 23 more cables to order and fix them permanently on to sma patch panel, I don't want to take on and off these, knowing in the past these connectors are not continuous use parts. Thanks for the part number.

Hi folks,

This is more a generic VNA question, but thought i'd ask.

I've seen a trick to "eliminate" the coax by calibrating via the OSL on the
far end of the coax, rather than having OSL connected directly to the VNA.

Essentially it's re-calibrated with the coax factored into the equation,
virtually moving the feedpoint to inside the shack for accurate antenna
feedpoint measurement.

If i calibrate the far end, take resonance readings, then recalibrate with
the OSL connected directly to the VNA, re-take resonance readings, would it
be safe to assume if there is common-mode current interference on the coax
it would account for differing results (if there are any)?

If there's no common-mode currents, the coax-length should be invisible.

Just want to make sure i've got my theory correct. :)



Thanks & 73s,

Chris.

30 mating cycles ?? That gets you through the Demo Board only
twice !!

Where can one get extra cables, I think I may need them if I am
to use the Demo Board to show off what the NanoVNA can do.

73, Dick, W1KSZ
________________________________
From: [email protected] <[email protected]> on behalf of reuterr@... <reuterr@...>
Sent: Tuesday, January 7, 2020 12:42 PM
To: [email protected] <[email protected]>
Subject: Re: [nanovna-users] Part Number for the Demokit Cable

ebay.com, eBay item number: 352840116109, $2.29 free shipping

Please see my documentation at:
/g/nanovna-users/wiki/RF-Demo-Kit-use

73, Rudi DL5FA

Hi again Jeff;

I believe I now sufficiently understand the technical aspects of the discussions in this thread to forego the wizardry behind the pursuit of high accuracy. it appears sufficiently sound.

On that happy note… I will state my one remaining question succinctly. Why the obsession over accuracy at the the two most unstable phase regions of highest Q and unreachable limits of infinity and zero?

A reasonable and credible answer will be a bounded tolerance of impedance or phase in those regions, and an estimate of the consequence of exceeding the tolerance boundaries.

I will reiterate… There is nothing wrong with how this is treated what is being done or the rationale behind the obsession. The only question is simply... Why?

--
73

Gary, N3GO

As luck would have it, Times Microwave website has a coax calculator that includes the delay! My feeder is 26cm of RG316, which comes out as 1.3nS. Was also pleased to find the nanovna allows delay to be entered in pS or nS!

The resulting traces for this antenna are very complex, but it does show the VSWR is good. The complexity I think is likely to be due to the multi-element groundplane arrangement of the antenna! but I will do more testing later.

How long is your feeder and what kind of, I assume, coax? It's really
quite easy. Give me those parameters, and I'll show you.

Dave - W?LEV

On Tue, Jan 7, 2020 at 7:19 PM Martin Barfield G7MRV <marting7mrv@...>
wrote:

That makes sense, thanks,

however the problem I have is that I cannot do it this way, due to the
antenna being fixed and not being able to access the feeder connection, so
it will need the maths!

So, its the electrical delay parameter thats needed, and this is in
picoseconds... I also know the length and the type of feeder, so should be
able to find the necessary parameters now to calculate the delay,

It would have been so much easier of course if i'd bought two of the same
patch leads, like I usually do!

Cheers
Martin

--

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

ebay.com, eBay item number: 352840116109, $2.29 free shipping

Please see my documentation at:
/g/nanovna-users/wiki/RF-Demo-Kit-use

73, Rudi DL5FA

That makes sense, thanks,

however the problem I have is that I cannot do it this way, due to the antenna being fixed and not being able to access the feeder connection, so it will need the maths!

So, its the electrical delay parameter thats needed, and this is in picoseconds... I also know the length and the type of feeder, so should be able to find the necessary parameters now to calculate the delay,

It would have been so much easier of course if i'd bought two of the same patch leads, like I usually do!

Cheers
Martin

On Tue, Jan 7, 2020 at 09:40 AM, vincent coppola wrote:

" ..The problem appears to be in determining the correct 3db points. Please note the band stop filter is the only filter that I have tried to measure Q .."
============================================================

Vince,
You might include a screen capture of showing the analysis data and the bandpass filter. If your filter is not flat in the bandpass, has large ripple in the bandpass, or there are not enough measurement points then an accurate automated determination of the 3 dB points may not be possible.

The program asks the user to place a marker in the flat area of the bandpass and then computes the lower and upper 3 dB frequency points from that marker value. The computed points may not correspond to any of your actual measurement points and the program will choose the closest point. For better accuracy, choose a higher number of sweep segments which will give more measurement points over the frequency range.

- Herb

Anyone have a part number on the Demokit Cable, I want to have more than just two cables for the kit?

Thanks,

73 de ke4pwe

Again, read the tutorials associated with the NANOVNA sites. Series and
parallel RLC circuits represent resonant circuits. The R represents the
lumped loss in these circuit configurations. They may be used in impedance
matching and filters of most kinds. Read up on resonance and you will
become enlightened as to their universal uses in all things RF.

Dave - W?LEV

On Tue, Jan 7, 2020 at 5:50 PM aa_talaat via Groups.Io <aa_talaat=
[email protected]> wrote:

Hi,
For the NanoVNA Mod 3 software, what is the use of Series and Parallel RLC
measurement? I guess in case of S11 measurement it would give me the series
and parallel impedance of the passive part under test in the form or RLC.
Is this the case?

What about S21 measurement, what would be their uses?

--

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

Hi,
For the NanoVNA Mod 3 software, what is the use of Series and Parallel RLC measurement? I guess in case of S11 measurement it would give me the series and parallel impedance of the passive part under test in the form or RLC. Is this the case?

What about S21 measurement, what would be their uses?

Ver 0.2.1. A very nice, usefull piece of software. The only problem I can see is when measuring Q in the band stop filter analysis mode, the value is incorrect and too low. The problem appears to be in determining the correct 3db points. Please note the band stop filter is the only filter that I have tried to measure Q. Thanks Vince

I believe this is the referenced book (attached photo and syllabus for the class below) - pulled from the parent directory of the handout directory.

Randy
NC8U

Lithium chemistry battery charges have a setting called "Storage Charge". Why? Because storing batteries with a full charge contributes to the swelling that you see. All my RC plane batteries are stored with a charge level of "Storage Charge" usually about half capacity. They keep a long time that way. Yes, I have to charge them before I use them.

I would advise that you put your nanoVNA away after using it without topping the battery. You'll have enough energy to make a quick test or two. If you anticipate needing to use it for a period of time, charge it up or leave it connected to your PC while you measure. But, then put it away with less than full charge.

If you suspect your unit has a drain current while it's on the shelf, charge it once in a while. Not fully. Just enough to bring it back to storage charge level. Don't forget, if you discharge a lithium battery down to about 3 volts per cell, you will likely ruin the battery.

Oh, and NEVER short them. They make GREAT fires.

BruceN / K4TQL

--
*"To invent, you need a good imagination and a pile of junk"* -- Thomas Alva Edison (1847-1931)

The RF Demo Kit NWDZ Rev-01-10 is available via Ebay for about 15 EUR.
A documentation can be found at: . I will just extend it a bit about details and *practical* *usage*.

For more *details* see the *wiki* *page*: /g/nanovna-users/wiki/RF-Demo-Kit-use

The micro coax plug is named U.FL/IPX, 50 Ohm, about 2mm diameter. For more details see on .

/!\ Excerpt: "Female U.FL connectors are not designed with reconnection in mind, and they are only rated for a few reconnects (approximately 30 mating cycles [5]) before replacement is needed. The female U.FL connectors are generally not sold separately, but rather as part of a pigtail with a high-quality 1.32 mm doubly shielded cable, which allows for a low-loss connection."

/!\ The cable crimp in the little U.FL connector in not very solid. In order to avoid a cable and plug separation you should solder the coax cable shield crimp, see the picture on the right.

I made once this experience, and it was very difficult to repair the cable connection. In order to fit the center wire, you need to solder it with very little tin, and open the socket a little with a needle. And you need some patience, good light and a good magnifier glass.

/!\ To make a connection with the U.FL coax plug, just use your finger, no tool. Use a little flat screw driver to lift off the U.FL female plug.

73, Rudi DL5FA

What does the VSWR trace look like?

*Clyde K. Spencer*

Add the Firefox Downloadthemall add-on to your FF browser. Takes < 1 minute to get all the files.

Hi Gary,

I just wanted to make that I answered your question as to why a Short and an Open are not plotted at -1 and +1 after calibration. (The short answer is: because their actual Gammas do not equal -1 and +1.)

As to the math, don't be daunted! It is more straight-forward than you might think. Keep in mind:

1. The basic formula for one-port error correction is based upon the one-port signal-flow graph.
2. Deriving an equation from a signal-flow graph might seem awkward, but there are a number of sites on the web that will give you the rules (if I could do it, I'm sure you can, too).
3. The result will be an equation that, after rearranging, will give you an actual Gamma in terms of a measured gamma and three error terms.
4. But you cannot use this equation to find an actual Gamma until the three error terms are known.
5. To find these error terms, you first make three S11 (Gamma) measurements, each measurement is of a device with a *known* Gamma (thus you need 3 devices of different known Gammas).
6. For each measurement, plug the measured Gamma and the "known" Gamma into the equation derived in step 3, above. This will give you three equations with three unknowns.
7. Solving for the unknowns (i.e. the errors) is linear algebra.

Best regards,

- Jeff, k6jca

I have had bad experiences with N connectors, even of the "precision" type
on high-quality equipment (interconnections between mainframe and S-parameter
test set on HP VNAs, for example). Getting a solid (resonance-free) connection
tends to require wrench tightening of the N connectors. And they are pretty
fragile with respect to mating male connectors of poor accuracy, particularly those
in which the center pin is positioned too far out. This is really too bad because
N connectors otherwise have a great deal good to offer.

My main concerns with SMA revolve around their fragility and their supposed
short life vis-a-vis connect / disconnect cycles. I believe that the SMA-like
3.5mm connectors are better on both counts.

Please, please, do not even think about BNC connectors. They have no place
whatsoever in any measurement application due to poor shield integrity. Also
these days they are being made with such sloppy tolerances that in some cases
mating or unmating requires excessive forces. TNC tend to be better, although
they are sufficiently rare that many people would complain.

My lab VNA (CMT S5048) uses N connectors, and I always use adapters to SMA
with them, in part in their role as "connector savers" so that the connectors on the
VNA see less wear. I feel that this is a reasonable compromise, subject to the
caveat about shield integrity, for which I check each time I do a calibration.

Dana