Designing Coiled Coax Ugly Baluns
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- čas přidán 10. 07. 2021
- Join John Portune, W6NBC/M0GCX to learn about how to design and use "ugly baluns"
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Great topic with really well explained usages and rationales. Just enough maths for hams who want to get it done, without needing to know the derivations.
The near field saturation especially in VHF/UHF will necessitate placing the choke at least 1/4 wl from the end of the nearest radial, element, etc.
Very true, I agree with you on your statement. That the coil would need to be at least a quarter wavelength below the base of the antenna. The question is is this a physical quarter wavelength of the same as the vertical radiator or are we talking the electrical quarter wavelength of the coax. Because then it gets really interesting, well calculating a choke for 103 megahertz. A quarter wavelength was only 18 in using rg213. I think it only extended a few more inches when I switched to rg400. Which is obviously far shorter than the physical free space quarter wave. So the question is at exactly what point and what version of a quarter wave would the choke coil need to be at.
Very clear explanations.
Just one of the reasons I like Ferrite chokes, as compared to ugly baluns, is that I worry that the large physical mass of the ugly balun will appreciably affect the shape of the RF field produced by the antenna.
I have seen improperly routed coax completely destroy the range of small radios. I realize that's not the entire affect in this case, but it is a part of it.
Great presentation John 👍. 73 de GI8WFA.
John, please explain to me why you stated that when a coax choke is self resonant, it works better when the theory behind an effective skin effect choke is to present a minimal inductive reactance of 200 ohms.
As to the question of making the CHOKE ,
" Square ", I took it to mean,
" As long, as it is Round " ?
6 inches long equal 6 inches in diameter ?
Not physically square ?
This was a great presentation! Thank you, and please make more :-)
Is there a reason on a dipole to put a choke at both the top and at the shack entrance?
Someone Please help me! why the coil inductance will only effect on the outside surface of the shield but not do the same thing with the inside surface of the shield?
A "square" coil was meant as one having the same length as width. Still a helix of coax, just the overall length and width being the same. Any advantage to that?
Since the shield is usually braided wires, the inside and outside surfaces are actually the same, as the wires weave in and out. So how does the return current know when and where to jump conductors, as they weave from inside to outside?
You're over thinking this by double. It's not following the individual strands of copper. The braid acts as one conductor.
It would be great if someone could just take both of these calculators and work them into a phone app or a single calculator. They already has your coax dimensions and common PVC pipe dimensions. If I'm kind of surprised it doesn't already exist. The one thing he doesn't touch on very much though is the size and dimensions for choke coils for vhf. 50 megahertz and up. I realize they would be small because that's in some cases where they're most needed.
Hi sir. What's the name of the site to calculate the choke balun? Greetings from the Netherlands.
Is it possible to have too much coax coiled up to act as an ugly balon? I have about 25 feet of Messi and Paploni UltraFlex 7 coiled up just below the antenna on my 10 meter dipole. KQ4OFQ, 73s.
Great presentation. Thank you. 73 PA5BAS
I think he has the ferrite mix data wrong. According to Palomar Engineer's web site mix 31 is for low HF (1 - 300 MHz), and mix 43 is for high HF (25-300 MHz).
I've never heard of microhenry's till now
When he was a kid they used to make fun of him, and now he spends his life overcompensating.
One thing that bothers me about these kinds of presentations, and they are common in the ham radio world, is lack of actual empirical evidence why this is important. My antenna without an ugly balun works fine. Show me how it will work better with an ugly balun, something more than take my word for it. I have added baluns/ununs to antennas because I read that I should, but any change in performance was imperceptible, so why do I need to do this?
i deleted my individual comments. There were too many of them. sheez..
Is it just me, or does this Ole' Boy lose his place a couple times, and invert his answers ?
No one else mentioned it ?
Especially where he discribed where a balun is placed on the open wire feeders !
Then earlier when describing what Mix to use at Vhf/Uhf ?
Addendum :
After reviewing the video, I did see where someone tried an over write, saying that the Balun for the coaxial fed dipole, goes at the Top !
Seems not enough attention to detail was made here !
This stuff is confusing enough as it is, to try and give the Old fellow a pass, because of age !
ARRL Staff can do a better job !
No reason not to correct these things !
This should be , Clear and Concise, if you're going to present them !
Just my 2 cents !
'73 !
I like it when 'learning networks' start with an accurate premise and accurate terminology. Coax coils are chokes, not baluns. Thumbs down.
G3TXQ (SK) did extensive testing. His work shows that coax inductors have a very narrow effective range and why they can very often make the common mode problem worse.
"Reactive chokes have the disadvantage that they can "resonate" with a [common mode] CM impedance path that is also reactive but of opposite sign - in some cases actually increasing the CM current flow rather than choking it..." That's why your friend made a proper wideband choke using ferrite cores - it's not an 'ugly balun with cores'...
www.karinya.net/g3txq/chokes/