Difference in SWR readings between nanoVNA and SWR meter

[OwO]

Another possibility that hasn't been mentioned so far is that your antenna doesn't have a good counterpoise and the ground cabling of your rig is acting as the other half of the antenna. Do a simple test: transmit 5 to 10W into the antenna and use a diode + LED probe on the outer conductor of your feed coax. If the LED lights up then the antenna should be considered unsafe to transmit >20W into.

[radiolistener]

Another possibility that hasn't been mentioned so far is that your antenna doesn't have a good counterpoise and the ground cabling of your rig is acting as the other half of the antenna. Do a simple test: transmit 5 to 10W into the antenna and use a diode + LED probe on the outer conductor of your feed coax. If the LED lights up then the antenna should be considered unsafe to transmit >20W into.

yes, he already had issues with different PSU, which have strong indication of presence common mode currents on the feeder. And now there is another confirmation that antenna is not good.

[Kleinstein]

If the difference is from grounding, one should also see this when measuring with the VNANano:  compare the old reading with the case of an additional ground connection (e.g. to the rig (turned off)).

[erikka]

Did you calibrate in the same range as the measurement?
Or did you calibrate the full 900MHz range.
For best results always calibrate in same range as measurement

[vinlove]

My rig has good ground connection, and also with the MFJ Artificial Ground.

Yes, nanoVNA has been calibrated for the same freq. range as the previous SWR readings. 1.8-30Mhz.   Exact same SWR readings.

[erikka]

The most simple test you can do on nanoVNA accuracy is a measure a resistor (short leads) and see if the value is measured correctly.
Many people use a 25 ohm resistor, e.g. two 50 calibration loads on a tee
If you if that measurement its possible to give feedback on the quality of you specific nanoVNA.
In general the accuracy of the nanoVNA below 300MHz is VERY good.

[Kleinstein]

If the SMR meter and VNA don'T agree, it may be a good idea to test the SWR meter at a point different from 1. So a test load (resistor) with intentional something like 1:2 SWR.  A broken/out of cal SWR meter may be OK at 1 and infinite but bad at 2.

[radiolistener]

Both may display correct SWR value. When it connected to a rig, there is a different common mode current configuration. Since he use unbalanced antenna powered with coax cable with no balun and no RF choke, it's SWR will depends on connection. And he already had issues with high RF interferences, so this is a clear indication that antenna is very unbalanced. May be bad counterpoise or a bad contact at antenna feed point.

[vinlove]

Hey Radiolistener

You sound like you have set up my antenna and radio   You are still keep talking about the faulty PSU which stayed here for a week, and returned.  Please wake up mate.

How do you think I have achieved 1:1 SWR on 7Mhz and 10Mhz  on my HF antenna, which is long wire?  It is inserted with 4:1 balun and also 1:1 choke and then coaxial cable. 

[Kleinstein]

I problem with grounding of the antenna is at least a very plausible explanation  why the instruments show different readings. One big difference likely is that the radio / SWR meter is connected to ground, while the nanoVNA is floated.  It it is a ground problem of the antenna, it should be viable in a measurement with the VNA: an extra external ground connection (e.g. to the radio) should than have an effect on the SWR reading. With an ideal Antenna sufficiently far away, it should have no effect.

[radiolistener]

How do you think I have achieved 1:1 SWR on 7Mhz and 10Mhz  on my HF antenna, which is long wire?  It is inserted with 4:1 balun and also 1:1 choke and then coaxial cable.

Do you talking about antenna which shows different VSWR?

Crazy PSU behavior during transmitting at high power and different VSWR taken when antenna is connected to your rig vs connected to VNA. All these things are strong indicator of common mode currents on the feeder due to unbalanced antenna with missing balun and missing RF choke on the feeder. This is because you're use broken antenna. It can be broken due weather influence or just a bad antenna.

There is still no screenshot of VNA screen with a Smith chart, taken for open, short and load. This is required to make sure that you're using properly calibrated and properly function VNA.

[vinlove]

Kleinstein,  Antenna was directly inserted into the VNA on its own for SWR sweep, not connected to the radio or ground.

The HF antenna works great. I make contacts on HF using the antenna everyday with great reports.
My new PSU is working great too. It is a large heavy duty PSU of 40A continuous one. Plenty of power and current. No problems at all.

I am just trying to test my new nanoVNA how accurate it is compared to my SWR meters, that is all.

You, RadioListener, seem to be in some illusion that i have some problem with PSU and antenna and the radios.   

[m3vuv]

i think radio listener is loosing the plot,just confuses the issue with his ill informed posts.

[radiolistener]

You, RadioListener, seem to be in some illusion that i have some problem with PSU and antenna and the radios.   Please read my posts carefully before you posting.

there is no illusion. You're arguing "I don't believe" and etc. But we are talking on technical forum, this is not religious forum.

Yes, you can do QSO with broken antenna. Yes, one PSU works, but other had crazy behavior. Yes, different SWR meters show the same VSWR for the same rig.

And yes, your antenna connected to your rig showing you different VSWR value than the same antenna connected to your VNA.

And all these things does not contradict the statement that there is an issue with your antenna. On the contrary, all these things confirms that there is a problem with the antenna.

If you don't understand it, I just stop to discuss this subject.

For some reason you're trying to ignore request for VNA screenshots with Smith chart for O,S,L loads to make sure that your VNA works properly.

For some reason you're trying to ignore request to measure VSWR with VNA with connected ground between NanoVNA and your rig.

So all it looks like trolling...

[radiolistener]

i think radio listener is loosing the plot,just confuses the issue with his ill informed posts.

The problem here is that vinlove don't know what is common mode current and how it can lead to different VSWR reading when the feeder connected to different equipment with different ground configuration. And why it will leads to crazy behavior of PSU and other electronics in the shack during transmission.

I'm not sure if he trolling deliberately (because he trying to ignore requests for VNA screenshots to make sure that his VNA works properly and to make sure that there is common mode currents) or just don't understand RF things. But it all gets tedious.

[vinlove]

I say I believe, when I am not 100% sure. It is nothing to do with religion. 

I don't have time to make screen shots of nanoVNA for this thread. It is quite simple problem.  There is difference in SWR readings between the nanoVNA and the analogue SWR meters. We are trying find what could cause that.  It could be the meters or the VNA or there might be some other factors.
That is all there too it.

I don't need look at Smith Charts and make Screen Shots.... bra bra, I mean what for?  What are you trying to prove?

Just because you think you are talking Science and Math, that doesn't mean you are 100% certain about everything in the universe, does it?

[vinlove]

i think radio listener is loosing the plot,just confuses the issue with his ill informed posts.

The problem here is that vinlove don't know what is common mode current and how it can lead to different VSWR reading when the feeder connected to different equipment with different ground configuration. And why it will leads to crazy behavior of PSU and other electronics in the shack during transmission.

I'm not sure if he trolling deliberately (because he trying to ignore requests for VNA screenshots to make sure that his VNA works properly and to make sure that there is common mode currents) or just don't understand RF things. But it all gets tedious.

You keep singing about common mode current here again.  Have you not got some other thing to sing about? It is getting boring.

Tell me, what you, yourself understand about the common mode current. Have you seen it? Have you touched or smelt it? You just read somebody's writing on the internet, and keep sining about it, whenever someone asks or talks about RF topics.  How does that help you making some good DX contacts or pleasurable CW QSOs on HF? Do you even have radio licence to transmit?

[radiolistener]

I don't have time to make screen shots of nanoVNA for this thread.

We don't have magic ball to see what happening with your antenna with no measurements.

There is difference in SWR readings between the nanoVNA and the analogue SWR meters. We are trying find what could cause that.

You already got pretty clean explanation why VNA and SWR meters will show you different VSWR value with broken antenna. If you don't believe it it's your problem.

If you're think this is not the case, then provide measurements. Otherwise further discussion are useless.

[vinlove]

I don't have time to make screen shots of nanoVNA for this thread.

We don't have magic ball to see what happening with your antenna with no measurements.

There is difference in SWR readings between the nanoVNA and the analogue SWR meters. We are trying find what could cause that.

You already got pretty clean explanation why VNA and SWR meters will show you different VSWR value with broken antenna. If you don't believe it it's your problem.

If you're think this is not the case, then provide measurements. Otherwise further discussion are useless.

You still haven't read my posts, and writing blindly about your imagination.  I don't have broken antenna. 

[radiolistener]

Do you even have radio licence to transmit?

I already answered on this question to you in the past. Yes, I have valid CEPT radio amateur license. My transceivers are registered and listed in my license.

Tell me, what you, yourself understand about the common mode current. Have you seen it? Have you touched or smelt it? You just read somebody's writing on the internet, and keep sining about it, whenever someone asks or talks about RF topics.  How does that help you making some good DX contacts or pleasurable CW QSOs on HF?

 



Just provide measurements, or stop that bullshit. This is the technical section of the forum, if you're want to talk about alternate physics and free energy, there is another section for that stuff: https://www.eevblog.com/forum/dodgy-technology/

[m3vuv]

in my view radiolistner gets fixated on an issue and blinkered,maybe  a clever fella but is comming over like a cock!

[radiolistener]

in my view radiolistner gets fixated on an issue

In my point of view, m3vuv and vinlove are just trolls. And I will not be surprised if those are two clones of the same people whose third clone was previously banned 

Just because:
1) trying to insulting and discuss personalities instead of technical subject

2) ignoring request to provide measurements, for example:

I don't have time to make screen shots of nanoVNA for this thread.

I don't need look at Smith Charts and make Screen Shots....

That's pretty clean trolling indicator.

3) talking "believe/don't believe" and trying to ignore technical explanation with absurd arguing, such as "I have QSO so antenna cannot have problem", etc.

4) wrote stupid and provocative things, for example:

Tell me, what you, yourself understand about the common mode current. Have you seen it? Have you touched or smelt it?

5) trying to switch subject of topic:

How does that help you making some good DX contacts or pleasurable CW QSOs on HF? Do you even have radio licence to transmit?

There is nothing to discuss in this thread anymore, because most possible root of cause already provided - unbalanced antenna with different counterpoise configuration for SWR and for VNA cases.

There are possible a lot of other possible issues, for example incorrect VNA calibration. But topic starter don't wan't to provide measurements to check it and trying to switch to discuss personalities. So, there is no sense for further discussion.

[fourfathom]

radiolistener is correct.  Perhaps not about the common-mode issue (or perhaps correct), but in general you can have a "broken" antenna and still make contacts.  And this "broken" antenna may indeed show wildly different SWR when measured with different instruments and different ground / shield connections. 

Example:  I've made contacts on 30 meters using a straightened paper clip shoved into the SWR meter "antenna" connector (transceiver <> autotuner <> SWR meter <> "broken" paper clip antenna).  There is no way that the SWR indicated by my SWR meter will be identical to that shown by my NanoVNA with the paper clip shoved into the VNA SMA connector.  The same would apply if I used 25 ft of coax between the measuring device and the paper clip.  Or if my antenna was a dipole without a feedline choke.  Or any antenna having common-mode current on the coax.

[OwO]

All it would take to prove or disprove the theory is to touch a piece of wire between the VNA SMA nut and the rig's coaxial connector ground, so why not just perform the experiment and settle the issue?

[cgroen]

I say I believe, when I am not 100% sure. It is nothing to do with religion. 

I don't have time to make screen shots of nanoVNA for this thread. It is quite simple problem.  There is difference in SWR readings between the nanoVNA and the analogue SWR meters. We are trying find what could cause that.  It could be the meters or the VNA or there might be some other factors.
That is all there too it.

I don't need look at Smith Charts and make Screen Shots.... bra bra, I mean what for?  What are you trying to prove?

Just because you think you are talking Science and Math, that doesn't mean you are 100% certain about everything in the universe, does it?

I'm not sure, but in my part of the world, taking a picture of a screen/screenshot takes substantially less time than writing x number of posts here 
Go on, provide the data and measurements. I will bet there is something fishy going on with your antenna/setup, but we will never know before you supply some concrete data and measurements....