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Real world. Interesting. If Hertz and Marconi stayed in the real world, would we have what we have now?

So, if the tool we have won't work, fine. I understand that. I have seen where random lengths of wires were bundled together and the return loss on various frequencies were charted. But I am not sure what tool was used or how the individual performed the test. That is why I am curious to know if the NanoVNA might be able to do this.

It is all good. Thanks guys for the reply.

Brian D
KF6BL

Brian,

to measure the resonances of that single wire, you need to extend it straight in clear air, far from any objects, connect it to the center pin of the NanoVNA's port, and connect the shell to an "infinite ground". That is a magical device that can take any current, at any frequency, without causing any voltage drop. That is, it's a zero-impedance sink.

When you only need to measure over a narrow frequency range, such an infinite ground is reasonably well approximated by several radial wires that are a quarter wave long each, and are out in the free air. But if you want to take a wire of random length, and measure its quarter wave length, this isn't good enough, because any little shift away from the resonant frequency of those radials will cause a change in the reading, and you can't separate the effect of the radial wires from that of the the random wire being measured.

A better approach to an infinite ground is a flat metal sheet that is several times larger than the quarter wavelength at the lowest frequency you will measure. Sometimes the sheet metal roof of a barn might be usable, but it's not very comfortable to climb up there to do measurements... And for UHF a car roof might suffice, but not really on VHF, let alone on lower frequencies.

Any imperfection of the ground you use will cause an error in your measurement, shifting the resonant frequencies you measure for the wire.

So my suggestion is this: Simple use two identical pieces of wire, and configure them as a dipole. Hang this dipole out in the clear, far away from any other objects, specially any conductive objects of significant size. Let the battery-powered NanoVNA dangle freely from that dipole. If the wires you are measuring are very much longer than the NanoVNA, then having the NanoVNA dangling there will cause very little error. But if the wires are short, then you need to isolate the instrument from the dipole, and that requires a good balun. Any imperfection of the balun, that introduces significant inductance or capacitance, will again cause an error in the measurement, and the presence of the NanoVNA near the wires will also change their resonant frequency. So better don't even try to measure short wires.

It turns out that an accurate measurement of a wire's real, own resonant frequency (or electrical length) is quite hard to do! And in practical applications, like antenna building, it's irrelevant to, because what you need to get right is the real resonance of the antenna, with all effects from nearby objects and of stuff connected to the antenna, like feedlines, balun, real (imperfect) ground, etc. In short, the real world, mentioned by Kent.

Manfred

Good morning Mikki from Atlanta Ga.

I have a question for you regarding the length of this wire. I have this
full wave 80m loop up in the air and would like to measure it and see where
the resonant points are located. would this work?

Fred - N4CLA

Years ago I needed to do some tests with a real TDR, so I put one together
using some CMOS chips. It worked quite well despite its simplicity. It
didn't care what the impedance of the transmission line was. Now I have a
real TDR - a Tek 1502.

Zack W9SZ

On Mon, Jun 20, 2022 at 7:16 AM KENT BRITAIN <WA5VJB@...> wrote:

Because the TDR is not really a TDR.
Using frequency sweeps it does a TDR like function.But it's just a VNA
doing calculations on the peaks and dips of a sweep.
Just a wire by itself is NOT a 50 Ohm transmission line.And the TDR like
function only works with 50 Ohm transmission line, and to someextent 72 Ohm
lines. Kent

On Monday, June 20, 2022, 05:37:46 AM CDT, DougVL <
k8rftradio@...> wrote:

The "TDR" function works - why shouldn't this?
It's simple enough to test, too!

--
Doug, K8RFT

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Can’t you just put it up as you intend to use it and find the low points in the SWR chart, or am I forgetting something? That way it would work against the counterpoise/ground plane that you intend to use.

--
Steve M0NMA

Yes, it is, I did it many times and it gives me repeatable results.
Simply connect the single wire into the S11 input (a cable with a PL239 socket here), I also ground the nanovna at the socket (the results are similar without the ground, it depends).
I do evaluate the |Z| then in the nanovna-saver.
Attached a picture from a real EFHW antenna measurement - the wire only.

You need to measure against a counter poise. Use 1 or more quarter wavelength radials connected to the ground connector shell of the nanovna. Try to replicate you operating position.

Mike N2MS

Because the TDR is not really a TDR.
Using frequency sweeps it does a TDR like function.But it's just a VNA doing calculations on the peaks and dips of a sweep.
Just a wire by itself is NOT a 50 Ohm transmission line.And the TDR like function only works with 50 Ohm transmission line, and to someextent 72 Ohm lines.? Kent

The "TDR" function works - why shouldn't this?
It's simple enough to test, too!

--
Doug, K8RFT

Hi Brian
The basic wavelength calculations would of course be your starting point.Height above ground, nearby objects, are all issues and again you really need a counterpoise to get a good reading.Welcome to the real world!? Kent

Thanks Kent. I wasn't looking at this from a 1/4 wave antenna perspective. I was looking at trying to find what frequencies can be found in a length of wire x feet long. I just happen to use the 234/length formula as an example from the math perspective.

So for another example, say I have a 16 foot length of 14AWG and want to know where the dips and peaks in the return loss are located. But I guess you are saying that in order to do this, I need something for that wire to work against. Would that be a correct thought? Possibly, a VNA of any type would be the wrong tool to use. This is why I am asking.

Regards,
Brian D
KF6BL

Not really
A 1/4 wave antenna is NON-FUNCTIONAL.
i.e. it does not work ........ by itself.
A 1/4 wave only works as a resonate antenna went mounted on a ground plane about 1/2 by 1/2 wavelengths.
So mount a connector in the middle of the roof of you car, have the NanoVNA on one side and the 1/4 wave element on the other side, and then you can find it's resonate frequency.?
Kent WA5VJB? Antenna Editor CQ Magazine.

We can use the time honored formula of 234/length to get the quarter wave frequency of a piece of wire. But... is there a way to connect that wire (e.g. 14AWG 7 strand insulated) to the NanoVNA and get the near resonant frequency?

Regards
Brian D
KF6BL

I recommend you have a look at this guide
/g/nanovna-users/files/Absolute%20Beginner%20Guide%20to%20The%20NanoVNA

I have an OG nanoVNA - about 2-1/2 years now and am thinking about updating the firmware. How do I find out the hardware version number and the firmware version number for my unit? I would like to find out those particulars prior to searching for compatible firmware

thanks

Yes, use the x64.zip file. No need for the source zip file. Extract the
zip, then click on the exe file to run it. Your older firmware should be
fine; you only need newer firmware if you want more features.

Roger,
Thanks for that info - I did have the right page but guess I didn't wait long enough fo the program to load. I should use the .64 program, since I have Win 10 as my OS, correct? Also, do I have to load the source code.zip file, or just leave it? And my current F/W is the 20201013 , will it be ok for the Nano saver program? A few other users have suggested some later F/W but I thought I'd work with the earlier F/W just to get used to the SAA-2N.
Thanks for your help, I'll let you know how things work out.
--
72/73 de k1qed, ?bob.c ? ? ? ? qrp 4evr!

On Sat, Jun 18, 2022 at 03:13 PM, Robert Coleman wrote:

For most of today I have been searching for a nano saver offering that works
with my SAA-2N and that will actually download. I've seen lots of github lists
of programs with no ".exe"in the program. i did find a group of zip files,
among them two with .64 and .86 which i tried. But they resulted in a small
black screen with the title above the screen but nothing in the screen. i do

This is the official NanoVNA Saver github release directory


When you start it you will get a black command box. Be patient It will take up to 20 seconds to load the program depending on your disk and computer speed. The reason is that there are a LOT of support and runtime files packaged in the .exe and they have to be unpacked and virus scanned (if you have anti-virus program installed).

**Note** Recent versions of NanoVNA Saver do not run on WIN 7 and WIN 8.1. I compiled versions that do run on these OS and you can find a link to them in another post I made a few months ago..

Roger

For most of today I have been searching for a nano saver offering that works with my SAA-2N and that will actually download. I've seen lots of github lists of programs with no ".exe"in the program. i did find a group of zip files, among them two with .64 and .86 which i tried. But they resulted in a small black screen with the title above the screen but nothing in the screen. i do have the Cypress drier loaded so that's not it. Can you point me to something that will work? i am using a lenovo with win 10 and I have loaded and used the vna-QT program with my SAA-2N, but the nano saver has much more to work with.
Thanks in advance for your help!
--
72/73 de k1qed, ?bob.c ? ? ? ? qrp 4evr!

That sounds great. Should I put the short cable on for calibration since it will be on for all testing that I have planned?Sent from my Galaxy Tab? S2

Yes, you always calibrate at the very end of the cable you are going to use then..