Difference in SWR readings between nanoVNA and SWR meter - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: November 29, 2019, 12:28:39 pm
content: I just did SWR reading on my HF antenna which is a EFLW with a balun.At 7.15 Mhz, my SWR meter off ATU is 1:1.1 SWR.On nanoVNA reading for the antenna at the same freq. is 1:2.87 SWR.That I would say is, a huge difference.Not sure which is right at this point and time.Obviously one is wrong, or both wrong.But it can't be both right?

author: vinlove
author_rank: Frequent Contributor
timestamp: November 29, 2019, 12:38:01 pm
content: I have tried with 2x other SWR meters (high quality ones), and they all read SWR as 1:1.1 at the freq. 7.15Mhz.nanoVNA is reading 1:2.87 SWR at 7.15 Mhz seems incorrect reading? I was using about 40W FM carrier for the SWR readings on the freq.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 29, 2019, 01:33:10 pm
content: If you have a "dummy load", which is (or should be) a known 50, you can check its VSWR with, first, the SWR meter, then with the VNA,-----both should give you the same result.If you have no dummy load, you should be able to check the VNA alone*with two 100metal film (not wirewound) resistors in parallel.*Fairly obviously, normal 1/4 & 1/2 watt resistors would not be suitable for transmitter output power.At 7.15MHz, any stray inductance or capacitance should have minimal effect.It is only of recent years that inexpensive VNAs have been available.Back when I did most of my RF testing, they were "rare as hen's teeth" & cost as much as a fairly nice car, so we usually used Scalar Network Analysers.

author: Kalvin
author_rank: Super Contributor
timestamp: November 29, 2019, 01:45:12 pm
content: Check also that you have calibrated your NanoVNA using the open/short/50ohm.

author: radiolistener
author_rank: Super Contributor
timestamp: November 29, 2019, 01:49:34 pm
content: In short, if you're using NanoVNA properly (performed calibration before measurement), it shows correct value.And your SWR meter shows wrong value.Scalar SWR meters have huge measurement error. For example, if you're using low power TX for measurement, your scalar SWR meter will show smaller value than real. Try to use at least 100-200 W power for SWR measurement with scalar meter, in such case it will show you more realistic value. But note, it may be dangerous for your rig, because SWR=2.9 is not good.As you can see, I was right when I told you that there is possible issue with your antenna in the topic about PSU.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 29, 2019, 02:05:37 pm
content: This guy has experienced errors with a NANO VNA compared to another VNA, so that makes the Vector -vs- Scalar argument a bit redundant.

author: Kalvin
author_rank: Super Contributor
timestamp: November 29, 2019, 02:16:31 pm
content: You can always compare your SWR-meter and NanoVNA with a known load. Just get a known resistor 25 ohms - 100 ohms and a capacitor or an inductor, and measure the SWR. Then compare the measurement values to the calculated value. You will have much less guesswork.

author: vinlove
author_rank: Frequent Contributor
timestamp: November 29, 2019, 02:19:06 pm
content: Great info !! Thanks.I just checked with a dummy load, and the nanoVNA shows flat 1:1 SWR across the band, as expected.But why the HF antenna which reads 1:1.02 on 3x different SWR meters (all high quality ones) is reading SWR 1:2.8 in the nanoVNA is a mystery to me.My rig has also inbuilt SWR meter, and it reads 1:1 on the 7Mhz with the HF antenna, so I have been using the HF antenna straight into the rig with just PWR/SWR meter all the time for ages with full 100W most of the time, and making loads of good contacts with good reports.

author: Kalvin
author_rank: Super Contributor
timestamp: November 29, 2019, 02:21:00 pm
content: Antenna may be picking a strong signal, and NanoVNA is quite sensitive device with small output power, so that may one cause that NanoVNA is showing high SWR.

author: Kalvin
author_rank: Super Contributor
timestamp: November 29, 2019, 03:51:16 pm
content: The effect of the received signal from the antenna might be reduced (although not completely eliminated) if NanoVNA could sweep by alternating TX on and TX off with some averaging, so that the background noise coming from the antenna could be canceled out, and the device should be able to provide somewhat improved SWR readings. I do not know how much improvement is possible, though.

author: radiolistener
author_rank: Super Contributor
timestamp: November 29, 2019, 10:19:13 pm
content: Quote from: vinlove on November 29, 2019, 02:19:06 pmMost of all because you're using too small power for SWR measurement with your SWR meter. Most of scalar SWR meters using diode as amplitude detector for a coupler output. The diode has limited working dynamic range and non-linear response at low voltage.This is why it will show you SWR=1.1 while in reality it is SWR=2.9. Just because amplitude taken from a coupler is too small for diode. It is small, because output power is too small.If you don't believe me, you can perform simple experiment to make sure that this is the truth. Just connect 75-100 Ohm resistor as a load on SWR meter and try to measure SWR at different power level. You will see that your SWR meter will show you SWR=1.0 at low power.75 Ohm resistor means SWR=1.5. But your SWR meter will show you SWR=1.0. Just because not enough power output was used for measurement.Almost all scalar SWR meters shows wrong SWR value at low power output.Another issue with scalar SWR meter is that it shows SWR value for entire bandwidth, it don't take into account that your TX has harmonics and out of band emissions. It show you average SWR value for all components in the signal.In opposite, VNA meters show you SWR value at specified frequency only. Also, VNA meters don't have diode issue (at low power output). This is why VNA measurement is more correct and more precise than scalar SWR meters.

author: radiolistener
author_rank: Super Contributor
timestamp: November 29, 2019, 10:34:35 pm
content: Quote from: vinlove on November 29, 2019, 02:19:06 pminbuild SWR meters have very bad measurement performance. They are not intended for precise measurement. The goal of inbuild SWR meters is just to protect your rig from burning out at very high SWR.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 30, 2019, 07:07:01 am
content: Quote from: vinlove on November 29, 2019, 02:19:06 pmHave you done the full check, which entails also checking the transmitter plus SWR meters into the dummy load?Also, try checking the SWR of your antenna at full power, if your SWR meters are rated for it.(do it fast, as other hams may look askance at a massive carrier up for too long)Write that down, then check at the lowest power level you can reduce the radio to.Write that down, also.Compare the two------ does it confirm the point made byradiolistener?Another test you can try, this time on the nanoVNA, is to use it to check the SWR with a 75load, then a 150loadThey should measure 1.5:1 & 3.0:1 respectively.I tend towardsKalvin'ssuggestion of interference from a strong external carrier.Back in the day, we occasionally needed to measure the return loss of the antenna bays of our TV site, over their designed range of frequencies.To do this, we used a Polyskop SWOB, which produced a swept RF signal, which was applied to the item under test, then detected the reflected signal & compared the two, to show return loss on a CRT screen.We had to wait for the TV Station next door to close down for the night, (stations did that back then) as the Polyskop was "as broad as a bull's bum", & would display their signal as errors.

author: vinlove
author_rank: Frequent Contributor
timestamp: November 30, 2019, 09:57:46 am
content: Will do more tests suggested over the weekend, and get back with the results.

author: vinlove
author_rank: Frequent Contributor
timestamp: November 30, 2019, 10:51:56 am
content: I don't quite agree or believe with Radiolistners simple suggestion that my rigs SWR meter is bad, and all 3x of my SWR meters are c%ap. Because the rigs is quite happy when it is transmitting via 1:1 SWR antenna.If SWR goes up to more than 1:2 on the inbuilt SWR meter, then it is not happy, and reduce the output power drastically. I always have to ensure the SWR is less than 1:1.5, and ideally 1:1 using the SWR meters and also inbuilt SWR meter. They all worked as the rig wanted when TXing for years.I have worked thousands of QSO with my HF antenna using full power 100W. And suddenly you get told all these SWR meters are useless and not working and only nanoVNA is the one to trust is a bit hard to take in.There must be some other factors involved in this situation.

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2019, 02:06:17 pm
content: Quote from: vinlove on November 30, 2019, 10:51:56 amIt doesn't matter believe it or not, it is really crap if you compare it with VNA.The same you may not believe in Ohm's law, but it still works despite the fact that you don't believe it.Scalar SWR meters is not intended for precise measurement. Especially at low transmission power. They are used just to estimate relative SWR level.Inbuild SWR meters are even worse than external SWR meters. Because the goal of inbuild SWR meter is not to measure SWR. Their goal is to protect your rig when SWR is too high. So they don't need to measure low SWR precisely. Their goal is just to estimate if SWR is acceptable or not. That's it.

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2019, 02:18:01 pm
content: Quote from: vinlove on November 30, 2019, 10:51:56 amThe thing that you didn't realized is that high SWR don't prevent QSO.High SWR just reduces efficiency of your transmitter-antenna system.With low efficiency you're needs to spend more power to get the same QSO.It is also may be dangerous for your rig, because it needs to dissipate more power into heat and needs to keep higher voltage on the amplifier output.Quote from: vinlove on November 30, 2019, 10:51:56 amI didn't told you that your SWR meters "are useless and not working". You can use it for SWRestimation.They are turns useless when you try to use it forprecise measurementof SWR. They are not intended for that purpose.It is possible to make scalar SWR meter more precise, in order to do that you're needs to replace diode detector with detectors on logarithmic amplifier, such asAD8310.With logarithmic detectors you can make your SWR more sensitive for low power transmission. But precision of such scalar SWR meter is still limited, due to linearity issues.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 30, 2019, 02:56:26 pm
content: Quote from: radiolistener on November 30, 2019, 02:18:01 pmI don't believe the OP is using an SWR meter for"precise measurements".The difference between an SWR of 1.1:1 & one of 2.87:1 is not a small change.If the dispute was between a VNA in a large box with "HP", "Anritsu", or "Rohde & Schwarz" on the front panel & a cheap SWR meter, I might be more inclined to agree with you, but a nanoVNA bought on the Internet is a cheap piece of equipment, of often unknown build quality or history.The "Scalar" term is normally used for "Scalar Analysers" like the Polyskop or similar, which can determine return loss to a high degree of accuracy.SWR can then be calculated if required.

author: Bud
author_rank: Super Contributor
timestamp: November 30, 2019, 04:01:33 pm
content: Quote from: vinlove on November 30, 2019, 10:51:56 amAll these cheap VNAs use wideband detectors, some have the bandwidth extending into GHz region. Any signals within the bandwidth of the detector will skew the measurements when their combined power is comparable with the dicky weak excitation signal of those VNAs. This is the factor you are looking for.The proper instruments have narrow band detectors and as such measure only at the frequency of interest. In order to use a half bees dick VNA to measure external aerials you have to connect it via a filter. Ideally via a bandpass filter that has a wider bandwidth than the antenna being measured, but you can try an LPF with say 10MHz cut off (for measurements at 7MHz) and see if that helps.

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2019, 08:56:29 pm
content: Quote from: Bud on November 30, 2019, 04:01:33 pmSWR meter has wideband detectors (just simple diode). VNA measures SWR value for specific frequency with very narrow bandwidth.But I think this is not the root of cause for his case. The reason is that he uses low power transmitter and since SWR is too small, the amplitude from reverse wave sensor is very low. It is not enough to open diode detector, so SWR meter just don't see reflected wave and shows low SWR. Just because power is too small and SWR value is not high enough to open diode.

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2019, 09:09:49 pm
content: Quote from: Bud on November 30, 2019, 04:01:33 pmyour words are correct with one exception, it is relevant for SWR meter, not for VNA.Yes, in order to get better reading from SWR meter, it's better to use bandpass filter on the SWR meter input.For VNA there is no needs band pass filter, because it already measure SWR for specific frequency with very narrow bandwidth. NanoVNA uses PLL synthesizer for frequency sweep and SA602 mixers to shift frequency down and digitize it with 48 kHz ADC, further processing is performed in digital domain.But again, filter cannot solve low SWR reading on SWR meter. Because this issue happens because voltage from refltected wave sensor is too low to open diode detector and SWR meter just cannot see reflected wave due to it's small amplitude.Since SWR meter cannot see reflected wave it shows low SWR. But things will be changed when transmitter power is very high or SWR is very high. In such case amplitude from reflected wave sensor will be high enough to open diode detector and SWR meter starts to see reflected wave and starts to show more correct SWR value. But it happens for high SWR.When SWR is low, classic SWR meter cannot measure it precisely.But NanoVNA can do it precisely, because it uses SA602 mixers and ADC with DSP for measurement instead of simple diode detector which is used in SWR meters

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2019, 09:21:12 pm
content: Quote from: vk6zgo on November 30, 2019, 02:56:26 pmI'm agree NanoVNA quality may depends on seller, and if topic starter has defective unit, it can show incorrect values.But if he uses good NanoVNA and performed proper calibration, the difference with "HP", "Anritsu", or "Rohde & Schwarz" will be noticed for SWR < 1.02 (40 dB dynamic range for S11). But if NanoVNA shows SWR=2.9, that's definitely not the case.I didn't noticed significant difference for S11 measurement with professional equipment. And cannot imagine the reason why it may have significant difference. I assume that NanoVNA works ok and properly calibrated. If we talking about defective unit, this is different story.Quote from: vk6zgo on November 30, 2019, 02:56:26 pmI'm agree "Scalar" term may be applied also for precise equipment. It just means that equipment measures value in scalar form instead of vector form.I mean classic SWR meters with diode detectors when I used word "scalar".

author: nali
author_rank: Frequent Contributor
timestamp: November 30, 2019, 09:56:19 pm
content: There's probably some other factor OP hasn't mentioned. Like, I doubt that his 100W rig is using SMA connectors so there must be a patch lead or adapter to the antenna lead. Is that performing OK? How was the nanoVNA calibrated - with patch lead / adapter or without?Would be interesting to see a S11 sweep or maybe a Smith plot over the band of interest.

author: radiolistener
author_rank: Super Contributor
timestamp: November 30, 2019, 10:19:21 pm
content: yes, I'm agree, first we needs to make sure that his NanoVNA works properly and has proper calibration.We needs screenshots taken with O, S and L loads on CH0 (S11) with enabled Smith chart trace.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 01, 2019, 03:52:33 pm
content: My rig is using a PL259 patch lead to the SWR meter, and to the antenna from the meter.I did calibration on the nanoVNA using all three Terminators for Open, Short and Load, and also Thru using the SMA pact cable.The result? = Same as before, nothing changed.So if I trim the antenna to bring down the SWR to 1:1 on the nanaVNA, making the SWr reading on the analogue SWR meter to shoot up, and if the rig does not function, then what?

author: OwO
author_rank: Super Contributor
timestamp: December 01, 2019, 04:34:38 pm
content: 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.

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2019, 05:26:23 pm
content: Quote from: OwO on December 01, 2019, 04:34:38 pmyes, 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 01, 2019, 05:27:35 pm
content: 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)).

author: erikka
author_rank: Regular Contributor
timestamp: December 01, 2019, 06:49:48 pm
content: 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

author: vinlove
author_rank: Frequent Contributor
timestamp: December 01, 2019, 08:38:44 pm
content: 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.

author: erikka
author_rank: Regular Contributor
timestamp: December 02, 2019, 08:12:17 am
content: 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 teeIf 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 02, 2019, 08:42:26 am
content: 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.

author: radiolistener
author_rank: Super Contributor
timestamp: December 02, 2019, 09:57:49 am
content: 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.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 02, 2019, 01:03:57 pm
content: Hey RadiolistenerYou sound like you have set up my antenna and radioYou 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 02, 2019, 02:43:34 pm
content: 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.

author: radiolistener
author_rank: Super Contributor
timestamp: December 02, 2019, 11:08:14 pm
content: Quote from: vinlove on December 02, 2019, 01:03:57 pmDo 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.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2019, 12:08:23 am
content: 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.

author: m3vuv
author_rank: Super Contributor
timestamp: December 03, 2019, 12:20:53 am
content: i think radio listener is loosing the plot,just confuses the issue with his ill informed posts.

author: radiolistener
author_rank: Super Contributor
timestamp: December 03, 2019, 12:39:15 am
content: Quote from: vinlove on December 03, 2019, 12:08:23 amthere 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...

author: radiolistener
author_rank: Super Contributor
timestamp: December 03, 2019, 12:54:39 am
content: Quote from: m3vuv on December 03, 2019, 12:20:53 amThe 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.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2019, 12:54:57 am
content: 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?

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2019, 12:59:46 am
content: Quote from: radiolistener on December 03, 2019, 12:54:39 amYou 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?

author: radiolistener
author_rank: Super Contributor
timestamp: December 03, 2019, 01:00:18 am
content: Quote from: vinlove on December 03, 2019, 12:54:57 amWe don't have magic ball to see what happening with your antenna with no measurements.Quote from: vinlove on December 03, 2019, 12:54:57 amYou 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.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2019, 01:04:05 am
content: Quote from: radiolistener on December 03, 2019, 01:00:18 amYou still haven't read my posts, and writing blindly about your imagination. I don't have broken antenna.

author: radiolistener
author_rank: Super Contributor
timestamp: December 03, 2019, 01:04:51 am
content: Quote from: vinlove on December 03, 2019, 12:59:46 amI 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.Quote from: vinlove on December 03, 2019, 12:59:46 amJust 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/

author: m3vuv
author_rank: Super Contributor
timestamp: December 03, 2019, 02:35:30 am
content: in my view radiolistner gets fixated on an issue and blinkered,maybe a clever fella but is comming over like a cock!

author: radiolistener
author_rank: Super Contributor
timestamp: December 03, 2019, 03:14:47 am
content: Quote from: m3vuv on December 03, 2019, 02:35:30 amIn 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 bannedJust because:1) trying to insulting and discuss personalities instead of technical subject2) ignoring request to provide measurements, for example:Quote from: vinlove on December 03, 2019, 12:54:57 amThat'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:Quote from: vinlove on December 03, 2019, 12:59:46 am5) trying to switch subject of topic:Quote from: vinlove on December 03, 2019, 12:59:46 amThere 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.

author: fourfathom
author_rank: Super Contributor
timestamp: December 03, 2019, 03:58:14 am
content: 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.

author: OwO
author_rank: Super Contributor
timestamp: December 03, 2019, 04:31:03 am
content: 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?

author: cgroen
author_rank: Unknown
timestamp: December 03, 2019, 05:00:19 am
content: Quote from: vinlove on December 03, 2019, 12:54:57 amI'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 hereGo 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....

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2019, 07:48:50 am
content: OK, mate it is not a big deal for me. It is just a 30£ nanoVNA, how accurate it is, I was just testing out.But RadioListener, you are the one who spray this forum with bullshit, not me.Read your own posts, and think. You are not interested in giving out anything helpful for the OP. You are only into putting down others points like a piece of dirt. You keep on going about the problems that doesn't exist.I would take the screen shots, if I trusted what you were saying, but I no longer take you as a serious forum member. Sorry.I don't want to go and do what you suggest to do, and get slagged off by you for the rest of this century, because that is what you get pleasure from.You go and do what you want, and what you think is right. I am going to stop wasting time reading any more of your post from this moment.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 03, 2019, 08:09:08 am
content: vinlove, this is not a specialist ham radio site.I would suggest taking your original query to QRZ.com, where there are many people with experience of the type of antenna you are using.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 03, 2019, 08:17:20 am
content: That is now what I am realising VK6ZGO.I think that Radiolistenr guy is a just short wave listener who has not even touched real transceiver and transmitting antenna in all of his life. He is just jealous and bitter at the real licensed Hams, because he failed to pass his HAM Radio Exam, it sounds like. He says that his radios and antennas are registered to somewhere. I have never heard of that kind of rubbish in my life.

author: radiolistener
author_rank: Super Contributor
timestamp: December 03, 2019, 08:32:47 am
content: Quote from: vinlove on December 03, 2019, 07:48:50 amNanoVNA is much more accurate than any of your SWR meters, if you have any.And you don't testing, you're trolling and insulting here. Nothing else.Quote from: vinlove on December 03, 2019, 07:48:50 amthe bullshit here is just your posts. And all what you're doing here is just trolling.People that needs help and answer won't write bullshit like that:Quote from: vinlove on December 03, 2019, 12:54:57 amA lot of people asked you to provide measurements. But you still continue to ignore that and now you're started to insulting.Quote from: vinlove on December 03, 2019, 08:17:20 amWhere you from?In my country the law requires government registration of transmitters and using unregistered transmitters is illegal even if you have license.For example, this how it looks in the license:

author: nali
author_rank: Frequent Contributor
timestamp: December 03, 2019, 10:02:12 am
content: Quote from: vinlove on December 03, 2019, 07:48:50 amvinloveIf you'd take a break from spitting your dummy out you might notice that it wasOwOwho actually brought up the subject of earthing & counterpoise. And from reading the content of his and your posts I'd say his knowledge on the subject is a good couple or orders of magnitude higher than your own.You're being given advice but not listening as it's not what you want to hear, a trait shared by at least one other in this thread.(and yes, I do hold an AR licence, have done for 25 years)

author: m3vuv
author_rank: Super Contributor
timestamp: December 03, 2019, 10:50:59 am
content: i think radiolisteners radios are maybe registered with chicken bands r us!

author: Yansi
author_rank: Super Contributor
timestamp: December 03, 2019, 02:53:17 pm
content: It's almost surprising how ignorant some people can be.

author: G7OVK
author_rank: Newbie
timestamp: December 03, 2019, 08:36:11 pm
content: Vinlove, I have read every comment in this thread by radiolistener, and everything he says is completely accurate. Your knowledge of the subject is clearly lacking, and you don't seem to be willing to accept what you're being told.You could start by providing the screenshots/information requested so that we can investigate further. If you're not willing to, don't expect to have your question properly resolved.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 04, 2019, 04:29:20 am
content: Quote from: G7OVK on December 03, 2019, 08:36:11 pmMuch of whatradiolistenersays, is indeed correct, but he, likevinlove, has become so absorbed in his narrative that he tends to "draw the long bow".For example, in dismissing the suggestion of interference from a nearby high powered RF source, he says:-For VNA there is no needs band pass filter, because it already measure SWR for specific frequency with very narrow bandwidth. NanoVNA uses PLL synthesizer for frequency sweep and SA602 mixers to shift frequency down and digitize it with 48 kHz ADC, further processing is performed in digital domain.From my reading of that, he is asserting that having high selectivity following the mixer will guarantee narrow bandwidth at the device input.This is, of course, not the case.Historically Superherodyne receivers have had at least one tuned circuit before the mixer, or at the very least a bandpass filter.With an untuned mixer &, effectively, a low IF, image interference is probable, as is intermodulation between the wanted frequency & even widely disparate frequency sources if they are strong enough.SWR bridges are normally so insensitive that they are used with high enough power levels to make direct reading of external carriers highly unlikely.Before the "chest beating" starts, I will state that I have been an Amateur Radio Operator since 1977.In my working career, I spent 30 plus years working with TV & Radio Broadcasting, the latter both FM & AM (MF & HF), as well as Communications transmitters & associated equipment, so maybe my opinion might just, possibly, be worth considering.My advice to the OP to take it to QRZ.com is based upon the fact that hams are a minority on this site, & QRZ has some people who are very experienced in the use of the type of antenna he has, & can give him advice which isn't associated with the ongoing "aggro" in this thread.Whether he choses to take it, is up tovinlove.

author: m3vuv
author_rank: Super Contributor
timestamp: December 04, 2019, 05:08:04 am
content: maybe this may help,found it on iogroups,sorted my issue out after pulling my hair out for almost 2 days! :Problem solved !I'm running the new Nanovna-Q software from Nov. 26.Before calibration I did the RESET, sure. The calibration resistors are OK, I have two, one that came with the NanoVna and one from MiniCircuits.The RESET procedure was the problem:I did not realize that I also need to SAVE to Cx right after Reset. Otherwise the data isn't really cleared and remains in the memory.If I remember correctly in previous firmware versions the RESET automatically cleared the memory loction without having to save actively.Whatsoever, now it works fine again. Thanks for your inputs !

author: radiolistener
author_rank: Super Contributor
timestamp: December 04, 2019, 05:17:28 am
content: Quote from: m3vuv on December 04, 2019, 05:08:04 amThis is incorrect information. There is no need to save calibration right after CAL RESET. Save is not required at all for calibration. You can save calibration at any time if it needs, but you can use calibration with no save until power off.Save is needed just to be able to recall calibration later, for example after power off.Also, when you're doing clearconfig command there is needs power off before any save operation, otherwise save operation will restore old bad configuration and it will needs to repeat clearconfig again.

author: OwO
author_rank: Super Contributor
timestamp: December 04, 2019, 05:38:14 am
content: Quote from: vk6zgo on December 04, 2019, 04:29:20 amThis is all true, but in a VNA it's very easy to tell between external interferers and the true S11 response - the signal generator and the LO are phase coherent (when mixed down to DC with DSP you get a constant, unchanging vector) whereas any external interferers will have a random phase at any given time (unless they are somehow phase-locked to the same crystal as the LO). Hence the request for a smith chart which will very clearly tell you if you have an interferer problem or not. An interferer will show up as a "noisy" or "jagged" smith chart while physical devices will tend to have a "smooth" response provided you have enough resolution. This is also why I always say a cheap shitty VNA is better than a decent SNA because in a SNA (other than a few "special" models that are just a VNA with phase hidden from the user) you can not tell between an interferer and the device response and so are always "flying blind".

author: m3vuv
author_rank: Super Contributor
timestamp: December 04, 2019, 06:29:42 am
content: Quote from: radiolistener on December 04, 2019, 05:17:28 am

author: radiolistener
author_rank: Super Contributor
timestamp: December 04, 2019, 06:38:59 am
content: Quote from: vk6zgo on December 04, 2019, 04:29:20 amThere is no bandpass filter on the mixers input in the NanoVNA, but as OwO mentioned above, REF and LO sources are phase coherent. And external sources are not coherent with REF and LO, so it doesn't affect measurement much. Of course if it's power level is not enough to overload mixers input.For example here is a small test.I connected 145 MHz antenna to NanoVNA and take measurement:After that I placed handheld radio near to antenna connected to NanoVNA and start transmission with about 5W power at 0.5 meter distance on 145.3 MHz and take second measurement on NanoVNA:As you understand, there is very strong interference from 5W transmitter near the measured antenna. But do you see any significant difference in VNA measurement?

author: radiolistener
author_rank: Super Contributor
timestamp: December 04, 2019, 06:42:48 am
content: Quote from: m3vuv on December 04, 2019, 06:29:42 amit gets more fun, especially when you wrote that you're using my firmware version.I wrote you how to properly use it and now you wrote that this is bullshit...

author: m3vuv
author_rank: Super Contributor
timestamp: December 04, 2019, 06:55:00 am
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: Caaarlo
author_rank: Newbie
timestamp: December 23, 2019, 06:44:44 pm
content: Quote from: vinlove on November 29, 2019, 12:28:39 pmI step in a bit late, but as far as I understand, you are using nanovna to measure the antenna directly, without ATU.Well... have in mind that after that point, towards the TX, the ATU is transforming whatever impedance your antenna has, to a value close to 50 ohms (and this is what the TX actually sees)... that's the reason for the SWR meter built into the TX, to show an almost perfect SWR. But when measuring the antenna alone using nanovna, or any SWR meter, it will show the actual VSWR without the ATU impedance transformation.If you bypass the ATU, or feed your antenna directly from the TX, then your SWR meter should read the actual SWR of your antenna, and it should be similar to the value shown by the nanovna (within a tolerance of 10% that analog meters usually have).In short: SWR along the TX-ATU line can be completely different from the SWR along the ATU-Antenna line, especially when using high impedance antennas like yours.

author: K0CRX
author_rank: Newbie
timestamp: February 14, 2020, 03:13:20 pm
content: I'm late to the show, too, but, I'll toss in my two cents. I'm a very new user of a NanoVNA and I am seeing differences in readings like vinlove.Using 160-meter off-center fed dipole -Freq 3.5 3.7 4.0NanoVNA 1.82 1.92 1.95 All instruments agree that the best match is at 3.3 mcAutek RF-1 H (>4:1) H HMFJ 207 3+ 3+ 3+Using 40-meter center fed dipole (might have a defective balun)-Freq 7.0 7.2 7.3NanoVNA 1.16 1.32 1.74Aurek RF-1 3.6 3.3 3.9MFJ 207 2.3 2.5 3+The VNA has been properly calibrated as per instructions. VNA measurements done using port CH0. All units agree on the point of lowest SWR, but, do not agree on the indicated SWR.Is it possible that we are using the wrong port? Should the unused port be terminated?

author: Yansi
author_rank: Super Contributor
timestamp: February 14, 2020, 03:37:47 pm
content: 160m dipole for 3,5 meg? Wtf3,5M is 80m band and the dipole size shall be 40m end to end.

author: chris_leyson
author_rank: Super Contributor
timestamp: February 14, 2020, 04:45:59 pm
content: I tend to agree with radiolistener regarding SWR meter accuracy particularly where power level is concerned. You could build a 20dB or 30dB directional coupler using a pair of Ferroxcube 4C65 toroids for example and measure the voltage on the forward and reflected ports.A long time ago I designed a 10kW 30dB directional coupler using 4C65 toroids and I think the core OD was about 35mm, I could be wrong about the OD maybe it was the next size up. Anyway, core area is determined by the lowest operating frequncy and peak flux density, 2MHz was the lowest operating frequency and I think the peak flux density was 30mT. I will have to run the numbers. Transformer directional couplers are not too difficult or expensive to build.10:1 turns ratio will give you 20dB coupling and 32:1 will give you 30 dB coupling. See fig. 17https://en.wikipedia.org/wiki/Power_dividers_and_directional_couplersAlsohttps://www.researchgate.net/publication/312570585_Design_and_development_of_a_dual_directional_coupler_with_transformers_for_HF_band_applications/link/5cf4a49ea6fdcc84750020fb/downloadEDIT: I forgot to add, what accuracy does you SWR meter claim over a given range of source and load impedance and through power. It's hardly metrology by any standard just a ball park indicator.Build a dummy load with a known SWR and then measure.Just cos you got an ameteur license doesn't make you an RF engineer, you've got to step up to the mark, understand the measurements your instruments are making and why they might be wrong it's basic physics, just saying.

author: metrologist
author_rank: Super Contributor
timestamp: February 14, 2020, 08:36:59 pm
content: Quote from: vinlove on November 29, 2019, 12:28:39 pmI was wondering, the ATU is measuring the tuned system. Is the VNA connected with the ATU not in line?

author: radiolistener
author_rank: Super Contributor
timestamp: February 15, 2020, 12:43:35 am
content: Quote from: K0CRX on February 14, 2020, 03:13:20 pmYou're needs to use CH0 port of NanoVNA for VSWR measurements. The second port CH1 no needs to be terminated. Also, make sure you're performed calibration and it works properly before measurement.Since you're using unbalanced antenna, you're measuring antenna with different ground configurations. Because unbalanced antenna using outer side of coax cable braid as a part of antenna, include metal case of your equipment. And even ground line of mains, if it has connection to the coax braid through metal case of your equipment.In short, you're needs to take care to prevent common mode currents from antenna through your equipment, otherwise you will see measurements for different antenna configuration. In such case you will see different VSWR values,but all of them are correct. Just because unbalanced antenna (with no RF choke and balun) connected to different equipment are different antennas.In order to test if you're measuring antenna instead of your equipment ground, just try to connect some long wire to the metal part of NanoVNA SMA connector (ground pin). With proper antenna it should not affect your measurement. But if you see different VSWR values with connected long wire, then there is a problem with your antenna. In such case you're needs to use RF choke, balun and ATU on the antenna side to eliminate such effect. Otherwise your antenna will be noisy and low efficient.The most easy way to reduce such effect is to use RF choke from coax line, something like that:This coil from coax line works as inductor for currents through outer side of coax braid, but it don't affect the signal inside coax cable.How many turns is needed depends on the frequency. Lower frequency requires more inductance, so it needs more turns. For 3.5 MHz 10-15 turns should be enough.This coil should be placed at distance about 1-2 meters from feeding point of antenna. Don't place it very close to antenna. For better performance you can place the same coil at the point where coax cable enters into your shack/building.Be prepared that sensitivity of your antenna with RF choke will be reduced. Because you will see just your real antenna performance with no affect of parasitic ground. But at the same time you will see less noise from your home equipment and better antenna efficiency.

author: chris_leyson
author_rank: Super Contributor
timestamp: February 15, 2020, 01:13:22 pm
content: I ran the numbers for a 30dB transformer coupler, N = 32 turns, Ferroxcube TX36/23/10 4C65 core,Ae = 64mm^2 = 0.64cm^2, P = 10,000W, Erms = 707V, f = 2MHz. In cgs units and assuming a sinewave then Bpk(Gauss) = Erms x 1E8 / (4.44 * Ae(cm^2) * N * f(Hz)) = 388 Gauss or 38.8mTThe next size up TX58/41/18 has Ae = 152mm^2 = 1.52cm^2, Bpk = 164Gauss = 16.4mT.I can't remember the exact core size but I do remember being a little aprehensive stuffing 10kW into it. The single or through winding is just the inner from some 50 Ohm coax with a copper tape shield grounded at one end. Somewhere I have a small 20dB coupler and will check it with a NanoVNA.

author: g0fvt
author_rank: Newbie
timestamp: March 25, 2020, 08:50:01 pm
content: IMHO two of the contributors to this thread have been bang on the money. I believe the issue is common mode current/lack of a counterpoise whilst checking with the VNA.

author: m3vuv
author_rank: Super Contributor
timestamp: March 26, 2020, 10:34:59 am
content: ive had mfj 259 analysers give crazy reading on some antennas,i think its some sort of voodoo at work!

author: shadowless
author_rank: Regular Contributor
timestamp: February 16, 2022, 05:39:04 am
content: I have been doing some testing with my nanovna for 140/440mhz. I keep getting crazy swr for the 140mhz band.I then tried to connect my nanovna to the pc in home of updating the firmware. That's when I found out that if I have the usb cable plug in while I use the device, I get more accurate result that is consistent with my swr meter. The antenna dip shift back to the 140mhz. If the nanovna is ran in the floating mode the 140 band is off as the antenna dip is shifted to 150 or even 160mhz.The usb cable connection probably provide the ground that is required for a more accurate testing for antennas. So far I have only tested the HT antennas, not done any testing on the larger antennas yet.I am not sure if that is the solution but I don't really trust using these device for antenna swr test over dedicated swr meters.

author: radiolistener
author_rank: Super Contributor
timestamp: February 16, 2022, 03:26:18 pm
content: Quote from: shadowless on February 16, 2022, 05:39:04 amThis is indication that your antenna has common mode current and it affects your measurements. This is why you see difference.Such result cannot be used to compare swr meter with nanovna. Just a wrong measurement method.