The challenge with the last choke is using individual wires. You are forming a transmission line from those individual wires, and the characteristic impedance is highly dependent on the pair spacing- not the number of wraps or doing a crossover or anything like that. In particular, the capacitance per unit length is highly sensitive to the pair spacing and the permittivity of the insulation. While it’s possible to get it close to 50 ohms, it will be very fidgety. That’s why you will almost always get better swr results by wrapping coax, since its conductors are already spaced properly by design.
Found this video series very informative and confirmed what I thought I already knew. The information is presented in a professional manner and was easy to follow. Great job, thanks.
Again, really good explanation of the terminology and the choke use-case. You certainly have a talent for getting your message across -- with just the right balance of theory, experimentation and 'cutting to the results' without making the viewer watch a complete test, 'soup to nuts' (as we Brits say.) Your 'disappointing' home made choke with parallel wires in your 'choke box' would probably be improved if you twisted the wires together as I suspect at least part of the problem is stray capacitive coupling at the higher frequencies that are messing up the 'balance' between 'inner' and 'outer' conductors and hence the SWR, -- a problem that does not occur when you use coax and either ferrite 'sleeve' or ferrite 'core.' You might also try 'crossing over' on the toroid at the 50% turns point winding half the toroid in the opposite direction. This also has the advantage of separating your 'input' from your 'output' as each will be at opposite side of the completed toroid. 73 Bruce G4ABX
Have you done a video comparing different wraps on the same type core? Your coax and power cables are just wrapped in one direction, some of your cores wrap left then cross through to right, and one split and went left and right. It would be awesome if you could show what the differences are!
Here is a link to my playlist where we test all kids of stuff: Learn about Chokes, Baluns and UnUns for Ham Radio Antennas ruclips.net/p/PLm8ROkpFeqoqkGQtBYfcT9Y-2GCKxBuuk
I bought a choke that performed worse than the one you made. I found that tying the pair of wires together at each loop around the toroid with dental floss kept the impedance constant and made the plot flat. One could tie the wires or tape them prior to winding, too.
Hi Ape - Thanks for sharing your experimental results. Since the focus of this video is on chokes, it seems (as I think another reader mentioned) that an attenuation measurement (S21) would be more revealing than a reflection (S11),or SWR, measurement. In fact I’m not sure how to interpret the reflection measurement results as I think they say more about impedance mismatches than they do about attenuation (i.e., choking). I guess some of the results leave me wondering as to the source(s) of impedance mismatch suggested in some of your plots. Interestingly, the commercial product ( short piece of coax wrapped in ferrite beads) showed essentially no variation in SWR versus frequency, which is kind of what I expect. Anyway, I’m not being critical of your results. Rather I’m trying to make sense of them. - Cheers! - Jim
Good video, as always. What is the length of the RG8 cable that you wrapped around the toroid at 1:44 in the video? I think that looks like an easy first choke project.
Would have liked to see the CMC attenuation on the last three chokes that you showed. Thanks for showing the disappointing results of your home brew core VSWR, I’ll be sure to test for that now.
Remark at 3:45 in the video "I" is not L .... "I" is the symbol for current like in Ohm's law or Kirchoff's law. It's confusing. It's not L1 coming in but I1 ... pronounced lke "eye 1" You guys in america happen to write "I" a lot meaning the letter L. That's why you probably say L in the video. Where talking about currents here .... not something else. In europe we make a clear difference between the two. "L" is voor coils .. meaning inductance. "I" is for current ... Ampère or Amps. Keep up this nice work. 73
Glad I wasn't the one to make this comment. It is appropriate, however. The capital "I" (here) sure looks like a small "l" (L) and on my keyboard (Logitech brand) there's no difference visible between the two. Still, should have known it's an "I" (a basic electronic symbol) as there's no inductance running up and down those conductors.
5:57 "What Ape Chokes" 😂😂😂 Are you using snap on ferrite cores for the other choke points? Or are you using the same choke you're demonstrating in all of those places as well?
Hi Ape. An equally informative video as part 1. I just bought my first HF radio and is planning on putting up a homebrew EFHW antenna with a 49:1 balun to connect to my radio. In my understanding the 49:1 balun will also act as a choke to eliminate CMC, since the connecting wires goes through a ferrite core (planning to buy 2 pcs of T240-43 for my balun). Am I correct in this assumption? Or am I missing something? Thank you for the help. 73 de 4G1FBL from the Philippines.
Hi Ape, I know this video was posted 2 years ago but was hoping you could offer some advice on this topic. I have LED overhead lights in my home and I cannot replace them as I am renting the place. These LEDs are causing interference. Diagonal lines show up on the waterfall display of my FT-991A as soon as I turn on the LED lights. The interference is visible on the VHF 2m / 144-166 MHz band but not on UHF 70cm / 430-440 MHz. It looks like the coax cable is picking this up and sending it into my radio. If I unplug the antenna, the waterfall turns black so the radio itself is not picking up the interference. I want to operate on VHF. What sort of choke/toroid mix could I use to suppress this interference going into my radio but allow my desired VHF signals to be transmitted ?
Mix 31 is good to about 200MHz if I recall correctly. Above that we will need to talk. CHeck out this site: palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection
@@TheSmokinApe Thanks so much, I'll give that a shot. My biggest dilemma is whether this sort of choke would negativity affect the signal going out from the radio. I just can't get my head around the fact that this stops the current on the outside of the shield but won't affect what's going on on the center conductor / inside the shield. Guess I have to read more..
@@TheSmokinApe Just to clarify... The problem is that the coax actually has 3 transmission paths, the outer surface of the shield, the inner surface of the shield, and the center conductor. Sorry for nit-picking, this just in case Mr Suku was thinking there were three individual "conductors" in the cable....
@@ohaya1 Just to clarify... The problem is that the coax actually has 3 transmission PATHS, the outer surface of the shield, the inner surface of the shield, and the center conductor. See "skin effect".
SK G3TXQ published a lot of his test results on different mixes as well as air core chokes. www.karinya.net/g3txq/chokes/ His recommendation was that you want to have as much of the impedance to be resistive at the frequencies of interest because inductive components can actually increase common mode current under some circumstances. I'm hoping to set up a fixture to use a NanoVNA for testing homebrew chokes. Thanks for the great videos!
Please explain.... what is the definition of "skin effect" (If that was a joke, I didn't get it) I understand the current flows on the shield to be just that.
The challenge with the last choke is using individual wires. You are forming a transmission line from those individual wires, and the characteristic impedance is highly dependent on the pair spacing- not the number of wraps or doing a crossover or anything like that. In particular, the capacitance per unit length is highly sensitive to the pair spacing and the permittivity of the insulation. While it’s possible to get it close to 50 ohms, it will be very fidgety. That’s why you will almost always get better swr results by wrapping coax, since its conductors are already spaced properly by design.
100% agreed
Found this video series very informative and confirmed what I thought I already knew. The information is presented in a professional manner and was easy to follow. Great job, thanks.
Glad you enjoyed it! Thanks Jim
Again, really good explanation of the terminology and the choke use-case. You certainly have a talent for getting your message across -- with just the right balance of theory, experimentation and 'cutting to the results' without making the viewer watch a complete test, 'soup to nuts' (as we Brits say.)
Your 'disappointing' home made choke with parallel wires in your 'choke box' would probably be improved if you twisted the wires together as I suspect at least part of the problem is stray capacitive coupling at the higher frequencies that are messing up the 'balance' between 'inner' and 'outer' conductors and hence the SWR, -- a problem that does not occur when you use coax and either ferrite 'sleeve' or ferrite 'core.'
You might also try 'crossing over' on the toroid at the 50% turns point winding half the toroid in the opposite direction. This also has the advantage of separating your 'input' from your 'output' as each will be at opposite side of the completed toroid. 73 Bruce G4ABX
Thanks for the info Bruce, I am looking at alternative wrappings. Stay tuned!
Good info
Thanks Tom
Have you done a video comparing different wraps on the same type core? Your coax and power cables are just wrapped in one direction, some of your cores wrap left then cross through to right, and one split and went left and right. It would be awesome if you could show what the differences are!
Here is a link to my playlist where we test all kids of stuff: Learn about Chokes, Baluns and UnUns for Ham Radio Antennas
ruclips.net/p/PLm8ROkpFeqoqkGQtBYfcT9Y-2GCKxBuuk
This. Well done. Nice setup before the demo. Good explanation of terms and a real experiment. Thanks!
Thanks Jim, I tried to lay it out in a way that made sense.
Loving this series on roids. Good stuff, Ape!
Hahaha... More to come!
Yinz are doing a good job.
Thanks 👍
I bought a choke that performed worse than the one you made. I found that tying the pair of wires together at each loop around the toroid with dental floss kept the impedance constant and made the plot flat. One could tie the wires or tape them prior to winding, too.
Dang, sorry to hear you had to mod it
Hi Ape - Thanks for sharing your experimental results. Since the focus of this video is on chokes, it seems (as I think another reader mentioned) that an attenuation measurement (S21) would be more revealing than a reflection (S11),or SWR, measurement. In fact I’m not sure how to interpret the reflection measurement results as I think they say more about impedance mismatches than they do about attenuation (i.e., choking). I guess some of the results leave me wondering as to the source(s) of impedance mismatch suggested in some of your plots. Interestingly, the commercial product ( short piece of coax wrapped in ferrite beads) showed essentially no variation in SWR versus frequency, which is kind of what I expect. Anyway, I’m not being critical of your results. Rather I’m trying to make sense of them. - Cheers! - Jim
Hey Jim, in part one I did the attenuation measurements and folks asked for a part 2 measuring swr.
Good video, as always. What is the length of the RG8 cable that you wrapped around the toroid at 1:44 in the video? I think that looks like an easy first choke project.
In the newer ones I have made I have used 36"
good
Thanks
Would have liked to see the CMC attenuation on the last three chokes that you showed. Thanks for showing the disappointing results of your home brew core VSWR, I’ll be sure to test for that now.
Hey John, sorry I didn't show it for the last there. I am planning more in the future.
More good info. Thanks!
Glad it was helpful!
Remark at 3:45 in the video
"I" is not L .... "I" is the symbol for current like in Ohm's law or Kirchoff's law. It's confusing. It's not L1 coming in but I1 ... pronounced lke "eye 1"
You guys in america happen to write "I" a lot meaning the letter L. That's why you probably say L in the video.
Where talking about currents here .... not something else.
In europe we make a clear difference between the two.
"L" is voor coils .. meaning inductance. "I" is for current ... Ampère or Amps.
Keep up this nice work. 73
Glad I wasn't the one to make this comment. It is appropriate, however. The capital "I" (here) sure looks like a small "l" (L) and on my keyboard (Logitech brand) there's no difference visible between the two. Still, should have known it's an "I" (a basic electronic symbol) as there's no inductance running up and down those conductors.
Can you just add the beads to your coax and just shrink-wrap them in place?
Sure can.
how much power one ft240-43 can withstand in this configuration with rg8 or with wire
What was the core material (and ring size that you used for the choke you compare to the Chameleon. I must have missed it.
T240-31
5:57 "What Ape Chokes" 😂😂😂 Are you using snap on ferrite cores for the other choke points? Or are you using the same choke you're demonstrating in all of those places as well?
Ah never mind you showed the other chokes you use right after
Hi Ape. An equally informative video as part 1.
I just bought my first HF radio and is planning on putting up a homebrew EFHW antenna with a 49:1 balun to connect to my radio. In my understanding the 49:1 balun will also act as a choke to eliminate CMC, since the connecting wires goes through a ferrite core (planning to buy 2 pcs of T240-43 for my balun). Am I correct in this assumption? Or am I missing something?
Thank you for the help.
73 de 4G1FBL from the Philippines.
Hey Elmore. The 49:1 will not act as a UNUN / transmatch and CMC choke, you will need to add a CMC choke if you want to use one.
@@TheSmokinApe thank you 👍
Hi Ape, I know this video was posted 2 years ago but was hoping you could offer some advice on this topic. I have LED overhead lights in my home and I cannot replace them as I am renting the place. These LEDs are causing interference. Diagonal lines show up on the waterfall display of my FT-991A as soon as I turn on the LED lights. The interference is visible on the VHF 2m / 144-166 MHz band but not on UHF 70cm / 430-440 MHz. It looks like the coax cable is picking this up and sending it into my radio. If I unplug the antenna, the waterfall turns black so the radio itself is not picking up the interference. I want to operate on VHF. What sort of choke/toroid mix could I use to suppress this interference going into my radio but allow my desired VHF signals to be transmitted ?
Mix 31 is good to about 200MHz if I recall correctly. Above that we will need to talk. CHeck out this site: palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection
@@TheSmokinApe Thanks so much, I'll give that a shot. My biggest dilemma is whether this sort of choke would negativity affect the signal going out from the radio. I just can't get my head around the fact that this stops the current on the outside of the shield but won't affect what's going on on the center conductor / inside the shield. Guess I have to read more..
It won't affect it. The problem is that the coax actually has 3 transmission lines, the outershield, innershield and the center conductor.
@@TheSmokinApe Just to clarify... The problem is that the coax actually has 3 transmission paths, the outer surface of the shield, the inner surface of the shield, and the center conductor. Sorry for nit-picking, this just in case Mr Suku was thinking there were three individual "conductors" in the cable....
@@ohaya1 Just to clarify... The problem is that the coax actually has 3 transmission PATHS, the outer surface of the shield, the inner surface of the shield, and the center conductor. See "skin effect".
Would a choke be appropriate on VHF where I have a certain frequency interference on receivng only from one repeater?
A choke like these wouldn't help.
Is it Toe-Roid or Tow-Roid?! Good info as always, man!
Both! Haha, this has me crying...
@@TheSmokinApe You're doing an awesome job, man! You're putting good information out there! :)
In other words, think of it as Tor - Oid...these two syllables.
Thats what I said son, Toe-roid
Awesome #2, ohhhh that didn't sound good! Lamo 😂
Lol 😆
SK G3TXQ published a lot of his test results on different mixes as well as air core chokes.
www.karinya.net/g3txq/chokes/
His recommendation was that you want to have as much of the impedance to be resistive at the frequencies of interest because inductive components can actually increase common mode current under some circumstances.
I'm hoping to set up a fixture to use a NanoVNA for testing homebrew chokes.
Thanks for the great videos!
I've referred to that site before, its a good one! Thanks for sharing... good luck with the VNA project 👍
That's not Skin Effect!
Glad you liked the video!
Please explain.... what is the definition of "skin effect" (If that was a joke, I didn't get it) I understand the current flows on the shield to be just that.
@@thomasnewbery7449 en.wikipedia.org/wiki/Skin_effect
Nice 'roids man
You know it!
be careful of 'roid rage. :-D
Always need to watch out for that 👍
Kewl qrz.com/db/kn6dam