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Maths is beautiful. Why do so many skip the pure elegance of it.

A video about your Common mode test board would be helpful for the folks that purchased one

You've probably figured this out by now, but when you keep saying you are making the circuit so that it is less resonant in that one place on the spectrum so much, what you are actually doing is lowering the "Q". Low "Q" equals wide bandwidth without the "performance" at any one frequency than you had before you started lowering said "Q". It's the same principal as the tank circuit in your vacuum tube linear amplifier. We shoot for about 12 "Q" because there we get a pretty wide bandwidth in which to work without making it so that when we go to tune it up on our frequency of choice within a band, we don't have so high a "Q" that if we breathe on the tuning capacitor we're not off into another band. I once built an amp with a "Q" of 40 or so and the tuning was so sharp that as the tubes warmed the amp up it would go out of resonance and I'd end up arcing everywhere because the plate circuit was so far out of resonance. A life lesson learned... Same thing applies here, though all you see is no help from the choke you designed. It's all about spreading that RF around nice and evenly and giving up performance where performance is not needed, as is in this case. It's all about trade-offs. Trade performance for function. 73 AA5IT

Good info but dude, your soldering needs some work.....LOL, Thanks for the video..

Excellent presentation-accessible to the newcomer but with enough information to whet an Elmer's appetite. It spurred me to buy the Halibut Electronics kit, and now I need to build ALL THE CURRENT CHOKES!

Wow, well taught! Thank you!

Excellent, excellent video…thanks for posting! 👍

I've no idea what is available to listen to on various satellites. How do I find out what is available and the associated frequency(ies) to listen to. I saw you at PACIFICON, but at the time you were tied up with two conversations, and I had to get back to the work I was doing at PACIFICON, for the event.

Maybe I missed this but why multiple common mode chokes are recommended (at feed point, at trx, in middle) and why single one at transceiver isn't enough for eliminating "bad things" entering trx?

Moore Margaret Harris Kimberly Perez Susan

5:28 ... "Necessarily balanced, becuzz physics" Dude! It's the TEM wave. Not deep physics. Though, of course, real coax isn't perfect so there's a tiny CM.

Lewis Dorothy Williams Melissa Allen Kimberly

Looks great. Can't wait for GA release. Now for the feature creep. Would be great to have a way of switching polarization remotely😂

Also looking forward to building this antenna. Thank you Smitty!

Excellent

It's been too long since I built a new antenna. Looking forward to this!

This is awesome! Very clever design! Excited to see all the EggNOGS in the wild, with a bit of cinnamon ;)

Great presentation! Is there a way that a NANO VNA can output it's choke results in the magnitude of "Z" rather than dB?

I tried to make a 1:1 today but my toroid seem to be smaller than all those yt examples.

Thanks a lot for this video, now it is clearer for me, except that you speak fast and for a non-english-speaker it's not easy to understand but i've seen it two times and it's ok now !😁

That's a GREAT video explaining Common Mode Chokes - One thing, you never talk about power handling ability since these are usually used with TX as well as RX situations. The air core coax wound chokes would be limited only by power handling of coax, or close depending on how much capacitance affected power handling. The ferrite cores would be my concern - I think even the clipon ferrites would handle 100 watts, but when 1000 watts is involved it would require more?

A question just came up in my mind: If you use two ferrites in series, does the separation between the two matter? IOW, does the flux from each one couple with that of the other one? I think I'll start saving up for a VNA. Also, I'm curious about one other thing *(NOT* related to coax). If I buy a pre-made common mode choke, can I connect one of the sets of windings backwards and turn it into a *DIFFERENTIAL* mode choke? How would that compare with using two *separate* inductors (wound on *different* cores) for that purpose? _73 de AF6AS_

_Cal Poly?_ Which one? I graduated from _Cal Poly, Pomona_ in 1976 with a BSEE. _73 de AF6AS_

What would happen if one were to place the common mode choke in an iron or aluminum tube? For instance, if someone were to insert a linear common mode choke into the support mast itself to protect the coaxial cable from weather elements like UV rays? What are the potential impacts, and have you ever measured them?

Is Halibut Electronics going to be at Dayton this year?

BTW: engineers do not build e.g. bridges by a "trial and error" approach 😅

I'm new to the hobby . . I have made a choke balun which i want to use near my HF radio, It is made of 240 mix 43 toroid and RG-58, my question is: is the distance between the balun and HF rig critical ? jumper i made will give me 8 inches distance b/w choke and radio

These are the answers about common mode that I have been looking for , for a long time. great lesson, thank you

Top presentation, graphics and explanation! I am yet to play with my VNA and just got some 31 mix torroids for this exact purpose. I have not seen anything like that test box but would like to build one. I have bookmarked the video for playlist to build. Perfect timing, thank you!👍🤠🇦🇺73 de VK1DON

Very good presentation and treatise of one of the most prevalent ham station basic problems....

Forgive my late input . I note in a few of the comments that many would love to see a comparison against a Coax bottle type Choke and what the attenuation figures come out like . . Great video by the way . Well done 73. Ron G4DIY

Hi, I find that a 1:1 choke will degrade my reception by 1-2 S. Is this ok? I have a choke on a toroid with 121 turns of coax

Excellent explanation and test work Mark. As another RF guy I am troubled by 2 things. One at 09:20, how can CM noise get inside a shielded radio when applied between coax shield and transceiver "ground"? I suspect all CM noise entry is either via poor coax or transceiver shielding. Two at 22:03 is the assumption that a CM choke should be X times the cable Zo. I doubt that the surge impedance on the outside of the coax is also 50 Ohms. Anybody wiser?

I took issue with the description of a coax as a differential cable early on in the talk (around 4 minutes). Signal Integrity engineers refer to them as single ended for a reason or two - a differential cable, for example requires at least 4 vna ports set into 2 logical port groups; and the shield is not the return conductor, it is a shield. It serves the same purpose as the shield over a twisted pair like in an ethernet cable, which is a true differential system. One more comment is that shields of coax are almost always tied to the chassis ground on both sides, not the signaling elements of a transceiver so there is no push-pull of currents. Any differential currents created are simply inductive coupling between the center conductor and the shield. That all said, I love the data collected on the experimental chokes the nanoVNA plots. I wish we could have seen data for 2 chokes placed on a single gordian knot to see how adding chokes improved the common mode rejection also.

FANTASTIC tutorial. 30+ year BSEE and Electromagnetic major here. You know your subject and can present it well. Thank you for all the work put into this.

I too have done some research and testing to determine the optimum ferrite materials and number of turns to get the most out of my RFI choke filters. I based my conclusions on ferrite manufacturers equations and my personal tests using signal generator, oscilloscope and nanoVNA to sweep the entire HF band (e.g. building a combined differential and common mode filter for the output of a home-brew DC switching power supply for my shack). I too found that, for a snap-on ferrite, 0.5 inch hole, type 31, 3 turns was optimal before capacitive coupling between turns reduced effectiveness. But for an FT-240-31 I think 5 to 7 was optimal, according to manufacturer's equations and testing (this was 3 years ago so I don't quite recall exactly). However, I also built a 1:1 current balun for use as a wire dipole feed point and I put 11 turns (16 AWG PTFE insulated wire, split and wound in two direction) on that one, and it tested extremely well, -35 dB attenuation across most of the HF band. So it seems the geometry of the toroid makes a big difference in terms of how many turns is optimal. And your tests also showed better braud-band attenuation with the 13 turns around a FT-140. Do you have a general explanation for this? Why does the capacitive coupling add up so much with the snap-ons?

I never bothered with chokes at one time but decided to try ferrite rings a few years ago. I looked at the G3TXQ site for information which rings to use and how many turns to use for a particular range of frequencies. No dipole of mine has ever been in the clear and my inverted vee is squashed into a 25' x 12' garden but, hey, it works! The first was on my 60m inverted vee at the aerial. It didn't seem to do much to stop r.f. getting down the coax and back into the shack. I then tried it inside the shack and it did stop r.f. getting back. I put two more at the aerial ends of my two coax cables to my five 20m to 10m dipoles in the attic. I did the same with these and put them in the shack. These are now in the shack as well. I came to the conclusion that r.f. was getting onto the cable after the choke so they might be better lower down the coax. If you think how long a wavelength is it can easily get on the coax below the choke. I've seen two aerial manufacturers say these two different things about where to put them. I also thought that two chokes, one at the aerial and one close to the tx might be a good idea. G4GHB.

Another benefit of the OHIS is user experience and ease of use. How many times have you purchased a headset or mic and didn't get the right adapter, or had to build your own adapter? How much time have you poured over pinout diagrams or relied on vague descriptions from some log forgotten blog post? Did you read the pinout backwards? Oops. Time to rewire or buy another connector. The user experience improvement benefits both device and radio makers.

16:00 - outer conductors of the two NanoVNA ports (at least on the old 1.5G one, the one made out of three SA612A mixers) are shorted through the device's common ground, just FYI

Excellent video brother

Thank you. Very nicely made and easy to understand.

Dude, you need to make more videos ! Good Job !

What if the coax has two shields, one inner foil and an outer braid?? Does that mean 5 currents?? How to wire up an RF choke with toroid ferrite??????

I think this is a good idea and not just for hams. There are plenty of devices with unusual audio interfaces outside of ham radio. Not as common but they're out there. I'm skeptical of the idea that manufacturers will put this interface in radios because my understanding is they make a big chunk of money off of selling accessories and if they have to compete for accessory sales they will be financially up a creek.

Very cool...and timely. It would be nice to add the CW Keying Line...but all out of pins, (maybe in CW mode the PTT line becomes the keying line). My interest is in being able to easily SWITCH between radios in my collection of rigs. I've just completed a modular desk project that allows me to physically arrange the equipment for ease of access. This standard helps tremendously with the switching project, even though my rigs' manufacture dates span decades. I look at the "Adapter Project" as a retrofit solution for legacy equipment. If all radio manufacturers, starting tomorrow, were to equip their radios, with OHIS ports and the headset, mic PTT switch manufacturers released their products with OHIS plugs, obviously no adapters would be needed; hence my view of the current status as a retrofit of legacy equipment. Various attempts have been made to produce products for RIG selection, but none that I've seen have taken the 40,000 foot view that you have...great work!

Good idea but how about a bluetooth interface with it too.

Nice presentation and it makes sense to test any balun before use to actually know what you are getting. Thank you and now I need to test.

Excellent thank you very much

Thanks for the video. As I was watching I was wandering about influences of possible phase shifts in the device. The influence on the working of the common mode choke. Signal coming in the choke (on one side) and signal comming in (on the opposite side and from the opposite direction) may have some phase shift. The load is probably not pure resistive....