Thanks so much Nigel. And good timing too. I was thinking earlier today to send you a TV show tomorrow instead of a radio show as usually hahaha. Yep... I just made a few more tests a little while ago and noticed that the coax version is influencing less the SWR that I have with no RF choke. So I guess I will do just the same. Less connectors to buy... more beers for me 😅. Summer in the camper is like on the boat with no wind 😅. 73, Nigel... happy Sunday my friend.
Being bilingual at times bites you, at 5:08 I believe you meant to say SMA (SubMiniature Version A) not SMD (Surface Mounted Device). This doesn’t take away from the overall quality of this excellent video. Thanks for sharing your experiments with us, it helps us to learn a lot. 73 WP4TGK
DUDE! By measuring only ONE HALF of the toroid winding, you're essentially measuring the RF rejection of a simple inductor used as a simple RF choke and NOT a "Common-Mode Choke". You need to connect the center taps of the NanoVNA to BOTH HALVES of the toroid winding (at input AND output to each NanoVNA center tap, respectively) and you should find that they deliver bettern than -40dB of "common-mode suppression or rejection". That's because with this test you're essentially trying to SEND current of the SAME polarity down BOTH SIDES of the CMC which is the definition of "common-mode current".
Still learning on how to make better measurements on anything related to amateur radio. The best part of the hobby is that there is always something new to learn for better results. So far I do things as I learned from 99% of the people doing measurements either here on RUclips or in real life. As long as I am "close" and I have an idea how a certain thing may work or how effective it is... I am happy. But I never say no when it comes to doing it better. 73, YO6DXE
5:30 to stop reflections on the screen, use a grey or dark coloured bed sheet over your head, camera and the VNA. Like a tent over you. The screen will be easily visible because it has it's own source of light. Even a white sheet may be better than nothing - try it if you have nothing else. But really, it's clear enough, so not a big problem. PS: great vid
Thanks so much. Ohh yes it would have been better. I know the trick but at times I have to make the videos on a rush so I skip many steps in order to finish filming faster 😅😅. I call it cheating as I have no other choice 😁. Cheers and 73, YO6DXE. P.S. I will try the polarizing filter next time as that one clearly removes all the reflections and stuff 😅.
If swr changes with chock it means you have common mode current on coax screen. For symetric dipole chock should be installed at antenna, for EFHW it could be installed just after 49:1 or after 5% lambda from it.
In theory yes, but I guess that would be valid if I would be transmitting. Otherwise I guess there would be no common mode current. When it comes to placing the choke, that is what I also know, only that it doesn't always seem to do the job well ( on the EFHW, on the dipole is ok ). I have a feeling that maybe the toroid used and the material may have an influence on the SWR change. Is not much though. If with no choke I have a good 1:1 on 7.030MHz for example, with the choke it would be the same but on 7.060MHz. I am still studying this 😅😅. 73, YO6DXE.
I suspect that the change in SWR is becuse your VSWR is being adversely affected by common-mode currents. That is to say: it is reading wrong, until you fit the choke and get a more correct reading. I have seen this many times in my old shack where all of my antennas were very imbalanced due to antenna layout and size problems. All of the antennas could be matched to a very good (1:1) VSWR, yet I always got bad RF burns because the rig and ATU case were hot with RF. I could not install a balanced antenna due to the shape of the garden. Once I fitted a good coax choke before the antenna switch (which was right at the input of the ATU) the best matched VSWR always read higher - 1.5:1 or 2:1 was the best match on some bands but there was no problem with unwanted RF voltages in th shack. As a bonus, rx QRM was lower too, and much lower TVI (this was 1990's so analogue TVs were difficult in my area) When I move to a new location in an apartment, I saw similar on a 21MHz 1/4wave vertical - the SWR would change at each position depending on the length of the coax - over 6 months I moved my rig further away from the antenna so added extra coax length. The VSWR reading dramatically changed depending on the coax length. This was a bad sign of common-mode currents on the coax. Again, I thought of the coax choke and once I fitted it, I had the a higher VSWR at but identical readings at every distance/coax length no matter if I operated from the living room, the kitchen bench or the far bedroom. Overall performance was much better despite higher VSWR readings. So my conclusion is that the VSWR meter does not read properly unless it carries no common-mode current The way my brain envisages it: freezing time for a split second, imaging the centre conductor showing 100 volts of RF at the meter diodes, but the coax shield being at 50 volts of RF - ie: the coax shield is "hot" with common mode. The difference between the two is 50 volts RF potential. Now, with no common-mode flow, the shield will be at 0V but the centre conductor will be at 100V, so there will be a much higher difference. So the meter diodes read a higher voltage, but gives a more true (higher) reading of VSWR with a common-mode choke. The meter is lying to you if it has common-mode flowing because it displays the ratios (the ratio difference of fwd:reflected) between the currents/voltages. If you measure the VSWR at the antenna feedpoint and then again at the back of the radio, with common-mode problems you get very different readings. But with a good common-mode choke, or a perfectly balanced antenna (or both) comparing your VSWR reading at both positions will ONLY be affected by coax attenuation (and even then, at HF and using good quality coax cables, this will not be a lot unless you have hundreds of metres of coax run) This is why some people think that coax length affects VSWR of the antenna. (they say "use exactly multiple of half wavelength coax " or "use only X metres of coax") The length shouldn't matter but it will appear to be so if there are common-mode problems.
I will be short because I have a long day today and still lots of work to finish, but I read it all and noted. Yes it makes sense indeed. Thank you so much for all the detailed info. This helps a lot because when you put ideas like this together things that to make sense. I guess that is why we always learn no matter how much we already know 😁. Cheers and have a fantastic rest of the week. 73, YO6DXE.
Very interesting. I wound choke with coax. As i remember it was 4 wound from one side and 4 from another side. I made it when my antenna wasn't matching. i had manual antenna tuner and it was arking and choke removed those problems. Back then i didn't had nano vna to check it, but it worked great for me
I think the first 1:1 RF choke I made was for my CB antenna... long time ago. It was made on a 15cm diameter PVC pipe and had a bunch of turns. It worked well but it looked like I have a pot hanging down from the antenna 😅😅.
I am also curious as it should make a difference since basically the inductance would be diferent. When things calm down with work a bit, I would like to return to this one and make more tests on this part. 😁😁
5:45 The test is correct in the procedure but the resulting attenuating level in decibel doesn't make sense because it is performed on 50 ohm VNA impedance but it is not the same impedance that common mode impedance will "see" on the external surface of the radianting coax braid. Vurthermore the choking is broadband and that impedance will vary enormously as the frequency varies. So the data in decibels can only be comparative but it is better in that case to refer to the reactance
I am sure is not exactly perfect. I am also still in the learning process to make more precise measurements. So far all I know is what I have learned from other fellow RUclips creators that made videos on this subject. But this is the beauty of the hobby.. always learning more and better ways to do things. 😁😁 73, YO6DXE
@@dxexplorer 783 / 5.000 Hi, physics and electronics in particular, should be studied with books to be sure not to acquire wrong information unless you choose well-known names e.g. W2AEW who, thanks to his past jobs, also knows how to explain very well (suggested to all my students). The situation about videos in italian is dramatic due to a very low level of the youngest Italian OMs and also, despite this, they make and publish videos with the claim to explain what they have not studied. This is how myths and legends are born and spread: this is the reason why I have written several articles with the aim of fighting them. The links are on my QRZ page; sorry, they are still only in Italian: I hope Google can help you, if you are interested. 73s
I am sorry to say this... but that I don't know as I am not so much into that. But technically do you actually need one ? Is not like you are putting 10W of wi-fi power into the antenna.
finally someone who both explains what he does and shows how he does it. I myself have a Nano VNA and now I know how to make a setup that shows how to measure a CMCC. I have a question, why do you make a connection between shields on the 2 connectors. with an external wire? and not the shield which is in coax
Hmmm. Common Mode Current flows on the outside of the coax braid (skin effect). You should be measuring the attenuation of CMC across the braid and not the center conductor.
@ke4tmt91 Yes it does, but technically a choke will use both conductors to become effective as you cannot supress something unless you see what you are suppressing 😁. So one conductors should be able to see what the other does so it will know what to do. Ok this is a funny explanation but the idea is that no matter what I measure, the inner conductor or the outside shield... the nanoVNA will show the same as the turns are identical. We are basically interested in how efficient it is and how much bandwidth we have. I want to see when I have time how the number of turns will affect this. 73, YO6DXE.
@@azarellediaz4892 I am only interested to measure one conductor since both windings are identical. And in practice they work one against each other canceling the currents passing trough. That is what I also understood so far from others that I learned from.
What type of coax did you use? RG-178? Are These thoroids both FT 140-43? And the final question: what diameter (or AWG number) of insulated copper wire?
The coax was just simple RG-58... but I tried to buy one that was more flexible and also I left it out in the sun to warm up and become even more flexible when making the turns on the toroid. The toroids are both FT140-43 yes. Its better to use 240-43 or 240-31 even better. I used what I had available. The insulated cover wire is 0.5mm no insulation / 1mm measured with the insulation.
Not sure how accurate it is, but in practice it does seem to show that the coax one is not as effective as the other one. Still lots to learn 😅😅. 73, YO6DXE and thank you for watching 🙏
I don't know that either. But since I like having all in enclosures I don't stress too much about that. Or if I would build the coax version and exclude the enclosure, most of the time I stay in the shade so again no stress 😅😅. 73, YO6DXE
Thanks so much. I also enjoy that one as well. It seems way more simple and with the latest tests ( off camera ) it also seems that is not changing much the SWR of the antenna as it is with no RF choke. So I think I will also stick to coax. 73, YO6DXE
@@dxexplorer I think the isolation is better for choking RF the coax shield does a good work. So you consider put another one at the beginnig of the line to avoid SWR bounce back? cheers (Ruben LU8ARM)
@RA-Arg I tried having one at the beginning of the line as well... actually I have been playing with it in all sort of positions... the best results I had with the RF choke at the end of the line. When I tried it at the beginning of the line ( at least with the EFHW antenna ) it was messing the SWR on all bands. Basically it was shifting the SWR up in frequency comparing to what it was with no RF choke at all. When it comes to the shield of the coax... indeed that is usually enough if there is a lot of coax on the ground especially. But if the coax is shorter or not much on the ground, then the RF choke comes in handy. I remember I tried a vertical last year and I always had bad reports ( I was using only 3m of coax ). As soon as I put the RF choke at the end of the line... boom... good reports only hahaha. So clearly I was getting common mode curent coming back in the transceiver messing up everything. I am still learning about this but is fun. 73.
I think many people missunderstand the way it works and how it gets measured as it seems to create a lot of confusion. The curents running through the cables.. either coax or two parallel wires will always work out of phase from each other... so no matter what wire I measure, the results will always be the same in practice. I kept searching on this and 99% of the people measure the same way and the results are very similar both in measurements and as well in practice. So honestly I don't really know other way to measure as the other 1% I got to read on were really badly made measurements that I really don't trust 😄. 73, YO6DXE
@@dxexplorer The coax version works on the idea of increasing the outside resistance to current flow. The wire version works on the idea that the resulting fields are opposite and will cancel out. It also works on the idea you are creating 2 x 100 ohm lines working in mirror with the end result being 50 ohms in and out. Tested properly.... you will see the coax version with not return the same attenuation level across as wider range. The wire version will kick it's arse! But the wire version will not be any good for down around 160m. Attenuation drops off very steeply down low and into the broadcast band (where I needed mind to work). I got recommended to try it too. Burnt my core out in 3 minutes (red hot) with 100w of AM on 1611 khz! Correctly tested you will see something like well over 25 to 30dB of attenuation from about 7mhz all the way up to 60mhz. But forget it on 160m or where I am on 1611 khz.... You will see the graph on the VNA under 18dB for the likes of 1611khz. The problem I had was I'm running low power AM services with short aerials. The aerial system was trying to use the coax feed back to the TX rack as part of the radial system (and the SWR dection in the TX was not liking it). So I needed to "choke off" the coax. The fix for me was the RG400 version aka the coax version here. But with a twist! I used the winding style and added a second choke. I wound it the same way but done with 2mm transformer wire. The two in series fixed it right up! Either one on their own was not so good. The version refered to here as the wire version - burnt out in no time as mentioned. Cheers 73's
@petertate3436 I come back tomorrow as is 2.30 am here 😅😅. Yes indeed this is how they work. But I measured the coax version the other way around too, basically measuring the outer braid and the results where very similar comparing to when I was measuring the center wire. On the frequency range to cover... I think it must be the material the core its made from. So far I only had the 43 on hand... I've heard 31 is better for chokes so I will try to get a few of those to test and see the results. For me with QRP power is easy life 😅😅. We chat soon. 73, YO6DXE
No no no... you just connect the coax to the BNC for example as normal... nothing unusual. You end up with one BNC in one side, and another one in the other side. One side goes to the transceiver and the other BNC to the antenna. Is just the one with the copper wire that you have to do the wire connections since you have two separate windings. One on the left one on the right. But there also you connect the BNC the same way as you would with a coax once you connected the wires together as in the video, because you end up the same with two in one side and two in the other side. I hope it makes sense, hard to explain I just woke up a little earlier 😅😅. 73, YO6DXE.
ох да, мои английский не очень хорош, но я вас смог понять))) в качестве balun 1:1 я бы советовал тот что мотается тремя проводами (ссылки тут размещать не получается) они у меня показали лучшие результаты чем такие из коаксиального кабеля или из двух проводов))) хотя в моем случае ферритовые кольца на которых я их мотал были далеко не лучшего качества)))
@piterstein9625 Хорошо, что вы поняли насколько. Про трехпроводной не знаю. Может быть, вы можете отправить мне электронное письмо со ссылкой, если у вас есть время. (это адрес электронной почты на странице контактов в блоге или в QRZ). Мне тоже интересно попробовать этот вариант. 😅😅
@@dxexplorer This balun can be easily found on Google by searching for “1:1 voltage balun” or “vk6ysf”. I took the design from the website of this radio amateur in the projects section. With the unnamed ferrite rings I have, this design showed very good results. )))
@@dxexplorer эту конструкцию можно найти на странице радиолюбителя VK6YSF в разделе проекты "BALUN 1:1 VOLTAGE".... надеюсь это сообщение модерация youtube все таки пропустит))))))
I did similar choke using enameled copper wire, and the parameters depended on the winding method. In my case, keeping black&white close to each others caused worse results, probably by adding capacitance. When I separated them to equal distance the difference was huge on plus.
I didn't got to test this but I was told in the past that usually thicker insulation on the wire helps in getting better results... so I guess is true. Thanks for this. Is good info to write it down. 73, YO6DXE
1000:1 may not be a good idea 😁😁. 1:1 may help a bit to make sure we do not have the common mode curent that bothers a lot especially when transmitting CW with a metalic key... and we get surprises in the fingers 😅. Also the TRX is happy when there is no common mode curent coming back into the transceiver 😁. 73, YO6DXE
@@dxexplorer Interesting book www.worldradiohistory.com/Archive-DX/QST/ARRL-Publications/ARRL%20Solid%20State%20Design%20for%20the%20Radio%20Amateur.pdf
My friend, it was a nice try but no banana. Not trying to be harsh, but you are showing impressionable newer hams the wrong way to test a CM choke. In all fairness you would remove this video until you can re-shoot it showing the proper method.
What is the proper way ? Asking because 99% of the hams I learned from use the same method. Taking in consideration the fact that I no longer have issues with common mode curent, they must be doing something right. 73, YO6DXE
Good video Chip. I use the coax version straight through to the radio, no joins. About 200mm from the radio. No problems with it.
Thanks so much Nigel. And good timing too. I was thinking earlier today to send you a TV show tomorrow instead of a radio show as usually hahaha. Yep... I just made a few more tests a little while ago and noticed that the coax version is influencing less the SWR that I have with no RF choke. So I guess I will do just the same. Less connectors to buy... more beers for me 😅. Summer in the camper is like on the boat with no wind 😅. 73, Nigel... happy Sunday my friend.
Being bilingual at times bites you, at 5:08 I believe you meant to say SMA (SubMiniature Version A) not SMD (Surface Mounted Device). This doesn’t take away from the overall quality of this excellent video. Thanks for sharing your experiments with us, it helps us to learn a lot.
73 WP4TGK
Yes yes SMA for sure 🤣🤣. Yes sometimes I need to rush to make the videos and my mind is all over the place 🤣. 73, YO6DXE
DUDE! By measuring only ONE HALF of the toroid winding, you're essentially measuring the RF rejection of a simple inductor used as a simple RF choke and NOT a "Common-Mode Choke". You need to connect the center taps of the NanoVNA to BOTH HALVES of the toroid winding (at input AND output to each NanoVNA center tap, respectively) and you should find that they deliver bettern than -40dB of "common-mode suppression or rejection". That's because with this test you're essentially trying to SEND current of the SAME polarity down BOTH SIDES of the CMC which is the definition of "common-mode current".
Is there a way to contact you for more information about this?
Still learning on how to make better measurements on anything related to amateur radio. The best part of the hobby is that there is always something new to learn for better results. So far I do things as I learned from 99% of the people doing measurements either here on RUclips or in real life. As long as I am "close" and I have an idea how a certain thing may work or how effective it is... I am happy. But I never say no when it comes to doing it better. 73, YO6DXE
5:30 to stop reflections on the screen, use a grey or dark coloured bed sheet over your head, camera and the VNA. Like a tent over you. The screen will be easily visible because it has it's own source of light. Even a white sheet may be better than nothing - try it if you have nothing else.
But really, it's clear enough, so not a big problem.
PS: great vid
Thanks so much. Ohh yes it would have been better. I know the trick but at times I have to make the videos on a rush so I skip many steps in order to finish filming faster 😅😅. I call it cheating as I have no other choice 😁. Cheers and 73, YO6DXE.
P.S. I will try the polarizing filter next time as that one clearly removes all the reflections and stuff 😅.
If swr changes with chock it means you have common mode current on coax screen. For symetric dipole chock should be installed at antenna, for EFHW it could be installed just after 49:1 or after 5% lambda from it.
In theory yes, but I guess that would be valid if I would be transmitting. Otherwise I guess there would be no common mode current. When it comes to placing the choke, that is what I also know, only that it doesn't always seem to do the job well ( on the EFHW, on the dipole is ok ). I have a feeling that maybe the toroid used and the material may have an influence on the SWR change. Is not much though. If with no choke I have a good 1:1 on 7.030MHz for example, with the choke it would be the same but on 7.060MHz. I am still studying this 😅😅. 73, YO6DXE.
I suspect that the change in SWR is becuse your VSWR is being adversely affected by common-mode currents. That is to say: it is reading wrong, until you fit the choke and get a more correct reading.
I have seen this many times in my old shack where all of my antennas were very imbalanced due to antenna layout and size problems. All of the antennas could be matched to a very good (1:1) VSWR, yet I always got bad RF burns because the rig and ATU case were hot with RF. I could not install a balanced antenna due to the shape of the garden.
Once I fitted a good coax choke before the antenna switch (which was right at the input of the ATU) the best matched VSWR always read higher - 1.5:1 or 2:1 was the best match on some bands but there was no problem with unwanted RF voltages in th shack. As a bonus, rx QRM was lower too, and much lower TVI (this was 1990's so analogue TVs were difficult in my area)
When I move to a new location in an apartment, I saw similar on a 21MHz 1/4wave vertical - the SWR would change at each position depending on the length of the coax - over 6 months I moved my rig further away from the antenna so added extra coax length. The VSWR reading dramatically changed depending on the coax length. This was a bad sign of common-mode currents on the coax.
Again, I thought of the coax choke and once I fitted it, I had the a higher VSWR at but identical readings at every distance/coax length no matter if I operated from the living room, the kitchen bench or the far bedroom. Overall performance was much better despite higher VSWR readings. So my conclusion is that the VSWR meter does not read properly unless it carries no common-mode current
The way my brain envisages it: freezing time for a split second, imaging the centre conductor showing 100 volts of RF at the meter diodes, but the coax shield being at 50 volts of RF - ie: the coax shield is "hot" with common mode. The difference between the two is 50 volts RF potential.
Now, with no common-mode flow, the shield will be at 0V but the centre conductor will be at 100V, so there will be a much higher difference. So the meter diodes read a higher voltage, but gives a more true (higher) reading of VSWR with a common-mode choke.
The meter is lying to you if it has common-mode flowing because it displays the ratios (the ratio difference of fwd:reflected) between the currents/voltages.
If you measure the VSWR at the antenna feedpoint and then again at the back of the radio, with common-mode problems you get very different readings. But with a good common-mode choke, or a perfectly balanced antenna (or both) comparing your VSWR reading at both positions will ONLY be affected by coax attenuation (and even then, at HF and using good quality coax cables, this will not be a lot unless you have hundreds of metres of coax run)
This is why some people think that coax length affects VSWR of the antenna. (they say "use exactly multiple of half wavelength coax " or "use only X metres of coax") The length shouldn't matter but it will appear to be so if there are common-mode problems.
I will be short because I have a long day today and still lots of work to finish, but I read it all and noted. Yes it makes sense indeed. Thank you so much for all the detailed info. This helps a lot because when you put ideas like this together things that to make sense. I guess that is why we always learn no matter how much we already know 😁. Cheers and have a fantastic rest of the week. 73, YO6DXE.
Very interesting. I wound choke with coax. As i remember it was 4 wound from one side and 4 from another side. I made it when my antenna wasn't matching. i had manual antenna tuner and it was arking and choke removed those problems. Back then i didn't had nano vna to check it, but it worked great for me
I think the first 1:1 RF choke I made was for my CB antenna... long time ago. It was made on a 15cm diameter PVC pipe and had a bunch of turns. It worked well but it looked like I have a pot hanging down from the antenna 😅😅.
@@dxexplorer imagine that 🤣. Yesterday I got my new transceiver yaesu ft-891. Now we can make contact whenever you will be ready 😁
@4L1LAT Ohhhh niiiiice.... maybe we can try this coming week. Not sure when I have the time but I will let you know in advance.
@@dxexplorer no problemo😄. Good luck my friend 73.
@4L1LAT excellent. We plan it and we try a QSO. I hope we are lucky with good propagation too. 73 my friend.
Thanks for this useful video, it was interesting to see how similar they are. I wonder if less turns made a difference.
I am also curious as it should make a difference since basically the inductance would be diferent. When things calm down with work a bit, I would like to return to this one and make more tests on this part. 😁😁
5:45 The test is correct in the procedure but the resulting attenuating level in decibel doesn't make sense because it is performed on 50 ohm VNA impedance but it is not the same impedance that common mode impedance will "see" on the external surface of the radianting coax braid.
Vurthermore the choking is broadband and that impedance will vary enormously as the frequency varies.
So the data in decibels can only be comparative but it is better in that case to refer to the reactance
I am sure is not exactly perfect. I am also still in the learning process to make more precise measurements. So far all I know is what I have learned from other fellow RUclips creators that made videos on this subject. But this is the beauty of the hobby.. always learning more and better ways to do things. 😁😁 73, YO6DXE
@@dxexplorer 783 / 5.000
Hi, physics and electronics in particular, should be studied with books to be sure not to acquire wrong information unless you choose well-known names e.g. W2AEW who, thanks to his past jobs, also knows how to explain very well (suggested to all my students).
The situation about videos in italian is dramatic due to a very low level of the youngest Italian OMs and also, despite this, they make and publish videos with the claim to explain what they have not studied.
This is how myths and legends are born and spread: this is the reason why I have written several articles with the aim of fighting them.
The links are on my QRZ page; sorry, they are still only in Italian: I hope Google can help you, if you are interested. 73s
hi
how to make a balun for 75 to 50 Ohms for 2.4 GHz WiFi ?
I am sorry to say this... but that I don't know as I am not so much into that. But technically do you actually need one ? Is not like you are putting 10W of wi-fi power into the antenna.
finally someone who both explains what he does and shows how he does it. I myself have a Nano VNA and now I know how to make a setup that shows how to measure a CMCC.
I have a question, why do you make a connection between shields on the 2 connectors.
with an external wire?
and not the shield which is in coax
Yes yes is very important to skip the shield and make the connection external in both cases either when using the coax or the parallel wires.
Hmmm. Common Mode Current flows on the outside of the coax braid (skin effect). You should be measuring the attenuation of CMC across the braid and not the center conductor.
@ke4tmt91 Yes it does, but technically a choke will use both conductors to become effective as you cannot supress something unless you see what you are suppressing 😁. So one conductors should be able to see what the other does so it will know what to do. Ok this is a funny explanation but the idea is that no matter what I measure, the inner conductor or the outside shield... the nanoVNA will show the same as the turns are identical. We are basically interested in how efficient it is and how much bandwidth we have. I want to see when I have time how the number of turns will affect this. 73, YO6DXE.
@@dxexplorersorry but this answer did not actually answer the question of why. You only said it’s important to not use the shield, why is that?
@@azarellediaz4892 I am only interested to measure one conductor since both windings are identical. And in practice they work one against each other canceling the currents passing trough. That is what I also understood so far from others that I learned from.
What measurements do you get with both of those inline?
I can't remember honestly but I will test when I get back home next week.
What type of coax did you use? RG-178? Are These thoroids both FT 140-43? And the final question: what diameter (or AWG number) of insulated copper wire?
The coax was just simple RG-58... but I tried to buy one that was more flexible and also I left it out in the sun to warm up and become even more flexible when making the turns on the toroid. The toroids are both FT140-43 yes. Its better to use 240-43 or 240-31 even better. I used what I had available. The insulated cover wire is 0.5mm no insulation / 1mm measured with the insulation.
@@dxexplorer Thank you!
@@АлександрКулеш-э3ж Always a pleasure buddy. 73
Connector loss at HF is minuscule, but fewer connectors means much higher reliability.
Less to worry about 😁. Especially when it comes to cheap ones that always have "surprises" 😅. 73, YO6DXE
Enjoyed your explaination and demonstration. 73, GL GD DL ZS1XB
Not sure how accurate it is, but in practice it does seem to show that the coax one is not as effective as the other one. Still lots to learn 😅😅. 73, YO6DXE and thank you for watching 🙏
That's nice
Thanks so much my friend. 73, YO6DXE
Not sure if ferrite cores are UV resistant.
I don't know that either. But since I like having all in enclosures I don't stress too much about that. Or if I would build the coax version and exclude the enclosure, most of the time I stay in the shade so again no stress 😅😅. 73, YO6DXE
Nice I prefer coax! cheers
Thanks so much. I also enjoy that one as well. It seems way more simple and with the latest tests ( off camera ) it also seems that is not changing much the SWR of the antenna as it is with no RF choke. So I think I will also stick to coax. 73, YO6DXE
@@dxexplorer I think the isolation is better for choking RF the coax shield does a good work.
So you consider put another one at the beginnig of the line to avoid SWR bounce back? cheers (Ruben LU8ARM)
@RA-Arg I tried having one at the beginning of the line as well... actually I have been playing with it in all sort of positions... the best results I had with the RF choke at the end of the line. When I tried it at the beginning of the line ( at least with the EFHW antenna ) it was messing the SWR on all bands. Basically it was shifting the SWR up in frequency comparing to what it was with no RF choke at all. When it comes to the shield of the coax... indeed that is usually enough if there is a lot of coax on the ground especially. But if the coax is shorter or not much on the ground, then the RF choke comes in handy. I remember I tried a vertical last year and I always had bad reports ( I was using only 3m of coax ). As soon as I put the RF choke at the end of the line... boom... good reports only hahaha. So clearly I was getting common mode curent coming back in the transceiver messing up everything. I am still learning about this but is fun. 73.
We are meant to be measuring Common Mode Attenuation. This flows on the OUTSIDE of the coax. PLEASE REVISE YOUR TEST JIGG!
I think many people missunderstand the way it works and how it gets measured as it seems to create a lot of confusion. The curents running through the cables.. either coax or two parallel wires will always work out of phase from each other... so no matter what wire I measure, the results will always be the same in practice. I kept searching on this and 99% of the people measure the same way and the results are very similar both in measurements and as well in practice. So honestly I don't really know other way to measure as the other 1% I got to read on were really badly made measurements that I really don't trust 😄. 73, YO6DXE
@@dxexplorer The coax version works on the idea of increasing the outside resistance to current flow. The wire version works on the idea that the resulting fields are opposite and will cancel out. It also works on the idea you are creating 2 x 100 ohm lines working in mirror with the end result being 50 ohms in and out.
Tested properly.... you will see the coax version with not return the same attenuation level across as wider range. The wire version will kick it's arse! But the wire version will not be any good for down around 160m. Attenuation drops off very steeply down low and into the broadcast band (where I needed mind to work). I got recommended to try it too. Burnt my core out in 3 minutes (red hot) with 100w of AM on 1611 khz! Correctly tested you will see something like well over 25 to 30dB of attenuation from about 7mhz all the way up to 60mhz. But forget it on 160m or where I am on 1611 khz.... You will see the graph on the VNA under 18dB for the likes of 1611khz.
The problem I had was I'm running low power AM services with short aerials. The aerial system was trying to use the coax feed back to the TX rack as part of the radial system (and the SWR dection in the TX was not liking it). So I needed to "choke off" the coax. The fix for me was the RG400 version aka the coax version here. But with a twist! I used the winding style and added a second choke. I wound it the same way but done with 2mm transformer wire. The two in series fixed it right up! Either one on their own was not so good. The version refered to here as the wire version - burnt out in no time as mentioned.
Cheers 73's
@petertate3436 I come back tomorrow as is 2.30 am here 😅😅. Yes indeed this is how they work. But I measured the coax version the other way around too, basically measuring the outer braid and the results where very similar comparing to when I was measuring the center wire. On the frequency range to cover... I think it must be the material the core its made from. So far I only had the 43 on hand... I've heard 31 is better for chokes so I will try to get a few of those to test and see the results. For me with QRP power is easy life 😅😅. We chat soon. 73, YO6DXE
Is it a SMA connector?
Yes.. but I only use this one for tests since the nanoVNA has the same connector, otherwise I use normal BNC connectors. 73, YO6DXE.
так оплетка же тоже является частью контура дросселя, а вы ее исключили замкнув вход с выходом
No no no... you just connect the coax to the BNC for example as normal... nothing unusual. You end up with one BNC in one side, and another one in the other side. One side goes to the transceiver and the other BNC to the antenna. Is just the one with the copper wire that you have to do the wire connections since you have two separate windings. One on the left one on the right. But there also you connect the BNC the same way as you would with a coax once you connected the wires together as in the video, because you end up the same with two in one side and two in the other side. I hope it makes sense, hard to explain I just woke up a little earlier 😅😅. 73, YO6DXE.
ох да, мои английский не очень хорош, но я вас смог понять))) в качестве balun 1:1 я бы советовал тот что мотается тремя проводами (ссылки тут размещать не получается) они у меня показали лучшие результаты чем такие из коаксиального кабеля или из двух проводов))) хотя в моем случае ферритовые кольца на которых я их мотал были далеко не лучшего качества)))
@piterstein9625 Хорошо, что вы поняли насколько. Про трехпроводной не знаю. Может быть, вы можете отправить мне электронное письмо со ссылкой, если у вас есть время. (это адрес электронной почты на странице контактов в блоге или в QRZ). Мне тоже интересно попробовать этот вариант. 😅😅
@@dxexplorer This balun can be easily found on Google by searching for “1:1 voltage balun” or “vk6ysf”. I took the design from the website of this radio amateur in the projects section. With the unnamed ferrite rings I have, this design showed very good results. )))
@@dxexplorer эту конструкцию можно найти на странице радиолюбителя VK6YSF в разделе проекты "BALUN 1:1 VOLTAGE".... надеюсь это сообщение модерация youtube все таки пропустит))))))
I did similar choke using enameled copper wire, and the parameters depended on the winding method. In my case, keeping black&white close to each others caused worse results, probably by adding capacitance. When I separated them to equal distance the difference was huge on plus.
I didn't got to test this but I was told in the past that usually thicker insulation on the wire helps in getting better results... so I guess is true. Thanks for this. Is good info to write it down. 73, YO6DXE
Why put a 1000:1 attenuator between TX and antenna ?
1000:1 may not be a good idea 😁😁. 1:1 may help a bit to make sure we do not have the common mode curent that bothers a lot especially when transmitting CW with a metalic key... and we get surprises in the fingers 😅. Also the TRX is happy when there is no common mode curent coming back into the transceiver 😁. 73, YO6DXE
@@dxexplorer Try a 3dB 50 ohm attenuator between TX and ATU, this limits the range of SWR seen by the TX.
@FarleyHillBilly I don't use an ATU. But I have this written down for the future... you never know 😁.
@@dxexplorer Interesting book
www.worldradiohistory.com/Archive-DX/QST/ARRL-Publications/ARRL%20Solid%20State%20Design%20for%20the%20Radio%20Amateur.pdf
@@FarleyHillBilly you want to waste half your power?
My friend, it was a nice try but no banana. Not trying to be harsh, but you are showing impressionable newer hams the wrong way to test a CM choke. In all fairness you would remove this video until you can re-shoot it showing the proper method.
What is the proper way ? Asking because 99% of the hams I learned from use the same method. Taking in consideration the fact that I no longer have issues with common mode curent, they must be doing something right. 73, YO6DXE