diy 1-1 unun - Page 1
Forum section: electronics / rf-microwave

author: p.larner
author_rank: Frequent Contributor
timestamp: April 04, 2024, 10:55:27 am
content: i have a 43 mix binocular core,i want to make a 1-1 unun using that and some rg-174 coax,how can i make it,wind etc,thanks in advance.

author: A.Z.
author_rank: Super Contributor
timestamp: April 04, 2024, 02:13:33 pm
content: are you asking about a 1:1 BalUn/Choke or what ?if so, just follow this by the letterhttps://www.dj0ip.de/rf-cmc-chokes/different-kinds-of-chokes/d2-guanella-choke/

author: p.larner
author_rank: Frequent Contributor
timestamp: April 04, 2024, 02:39:00 pm
content: Hi,its for connecting my 300 ohm antenna feeder to the input of an atu-100 atu so i assume its a 1-1 unun i need,i have an ft-240-43 core but no room in the case for that,but the binocular core would fit,i just am not 100% sure on the winding details ok 73.

author: A.Z.
author_rank: Super Contributor
timestamp: April 04, 2024, 02:50:53 pm
content: Quote from: p.larner on April 04, 2024, 02:39:00 pmOk, so follow the directions at the link I posted, connect the BalUn to the ATU using some coax (leave it outside the ATU) and connect the other end to the two conductors of your balanced line, all the infos you need are at the link, just focus on it and read carefully

author: vk4ffab
author_rank: Frequent Contributor
timestamp: April 04, 2024, 09:44:29 pm
content: Quote from: p.larner on April 04, 2024, 10:55:27 amWind the coax in one hole, out the other, over and over again. Nothing difficult here, a single winding on a binocular core is in one hole out the other in a U shape. If you can get 2 or 3 windings on that core you are good to go. Connector on one end to the transmatch, solder the other end direct to the open line feeder. BOOM, DONE! Probably better to do that on a larger single core or to use 1mm enameled wire on the binocular core. The largest binocular core I have is good to 100w, but the holes are not big enough for enough windings using 174 coax to get decent choking.

author: p.larner
author_rank: Frequent Contributor
timestamp: April 04, 2024, 09:52:42 pm
content: az cheers for the link but theres no mention of any ununs wound on a binocularcore tho,they are torroid rings not binocular cores.

author: Andy Chee
author_rank: Super Contributor
timestamp: April 05, 2024, 05:24:35 am
content: This is one winding on a binocular core:I don't know how many turns of RG-174 you'll be able to fit, but if you can, use the same number of turns as if you were winding a toroid. Otherwise just fit as many as you can.The input and output terminations will be exactly the same as a toroid.

author: A.Z.
author_rank: Super Contributor
timestamp: April 05, 2024, 07:56:10 am
content: Quote from: p.larner on April 04, 2024, 09:52:42 pmFirst, you will need a BalUn (from BALanced-UNbalanced) since you're connecting a BALanced line to an UNbalanced one (your ATU), then, as for the binocular core, which type/material is it ? Or, if you don't know that, what's the size of that core ? Because, see, aside from some pretty large binocular cores, most of them don't have enough room for the needed windings, that's why people prefers using toroidal cores, and since you wrote you have an FT240-43, I think you'd better consider using it and placing the unit outside your ATU and not inside it and there are some reasons to place it therehttps://www.dj0ip.de/balun-stuff/tuner-baluns/also seehttps://www.dj0ip.de/balun-stuff/tuner-baluns/d-i-y-tuner-balun/

author: A.Z.
author_rank: Super Contributor
timestamp: April 09, 2024, 06:05:14 pm
content: ok ... as usual, didn't expect anything else

author: p.larner
author_rank: Frequent Contributor
timestamp: April 10, 2024, 09:42:24 am
content: the point of using a binocular core was down to room,its to fit inside an at-100 kit,there is not room for a torroid,this is why i asked the question in the first place ok.

author: A.Z.
author_rank: Super Contributor
timestamp: April 10, 2024, 01:17:54 pm
content: ok, despite what was written, you WANT to use a SMALL binocular core, go on, do it and when you'll discover it doesn't work as expected and it cannot support your TX power come back and open another discussion ... as usual

author: vk4ffab
author_rank: Frequent Contributor
timestamp: April 10, 2024, 09:34:12 pm
content: Quote from: p.larner on April 10, 2024, 09:42:24 amOK, we have been giving you bad information from a lack of information. You do not want to wind this as a current balun IE a common mode choke, you do not want your little binocular acting as a choke it does not have the mass to dissipate the heat. Rather you want to wind this as a voltage balun. The smaller binocular should be fine to 100w would this way. Using 0.5mm wire minimum, you want 5T primary and 5T secondary and that will make the single ended output of the tuner, differential for the open wire feed antenna.

author: p.larner
author_rank: Frequent Contributor
timestamp: April 11, 2024, 08:43:02 am
content: Ok i have had a rethink on this,i will use a ft-43 torroid,is it ok to have it mounted in an eddystone type cast aluminium box?.or will the metal box affect it?.

author: A.Z.
author_rank: Super Contributor
timestamp: April 11, 2024, 09:02:05 am
content: no metal box, it will affect the currents flowing over the braid use a "plastic" box, a simple electrical junction box will fit

author: A.Z.
author_rank: Super Contributor
timestamp: April 11, 2024, 10:28:28 am
content: As for the 1:1 BalUn/Choke, follow the directions herehttps://www.dj0ip.de/balun-stuff/tuner-baluns/d-i-y-tuner-balun/and you won't be wrong, place it into a plastic box, put a panel connector at one side and two binding posts at the other and you'll have it, using an FT240-43 toRoid (ONE "R" not TWO) it will serve you well from 80 to 10 meters and will also work on 160; notice that the "favors..." annotations at the above page mean that on the reported bands the CM impedance will be higher so the unit will be more efficient, but it will also work on the other bands, the idea is to "favor" the bands where your antenna tuning is "critical"; in general my choice is to wind 17 turns on an FT240-43, the above links also contains detailed instructions showing how to properly wind the toroid

author: p.larner
author_rank: Frequent Contributor
timestamp: April 14, 2024, 04:30:05 pm
content: can i use side by side speaker wire and wind it the same as the pic?, Or is rg-58 a must ?.

author: p.larner
author_rank: Frequent Contributor
timestamp: April 14, 2024, 04:37:00 pm
content: also can this be mounted in a metal box if the two binding posts for the ladder line and the outer of the so-259 are insulated from the box?.

author: A.Z.
author_rank: Super Contributor
timestamp: April 14, 2024, 05:18:29 pm
content: reread the link and my previous post, do not screw things.

author: p.larner
author_rank: Frequent Contributor
timestamp: April 14, 2024, 06:31:06 pm
content: Then please explaine how that answers my question on does rg-58 have to be used, Or are you just trolling??.

author: A.Z.
author_rank: Super Contributor
timestamp: April 14, 2024, 07:24:14 pm
content: the type of coax is clearly stated at the link I already posted, just a matter of reading with a bit of ATTENTION, no trolling aside from YOURS

author: vk4ffab
author_rank: Frequent Contributor
timestamp: April 14, 2024, 08:37:41 pm
content: Quote from: p.larner on April 14, 2024, 04:30:05 pmA transmission line is a transmission line yeah? None of my baluns are wound using coax. They are all wound using teflon sleeved enameled copper wire. Using speaker wire, as long as its of a suitable gauge for the power handling is perfectly fine. Its also easier to deal with when it comes to soldering on lugs for connecting to binding posts.

author: p.larner
author_rank: Frequent Contributor
timestamp: April 14, 2024, 08:54:38 pm
content: thanks for a sensible answer from the vk4, is it ok mounted in a metal case as long as the banana posts for the ladderline are insulated from the box, Also can i wind it the same as in the pic i posted, Same number of turns etc?.

author: A.Z.
author_rank: Super Contributor
timestamp: April 14, 2024, 09:07:47 pm
content: no, putting it inside metal box means that you did not understand how and why it works, fine, go on and blame yourself

author: vk4ffab
author_rank: Frequent Contributor
timestamp: April 14, 2024, 09:27:38 pm
content: Quote from: p.larner on April 14, 2024, 08:54:38 pmI do not have a suitable answer to that. My gut says it depends. I mean, think of an antenna tuner, the old school balanced ones, big air caps, big roller inductor, big balun all sitting in a metal box. They do not seem to have a proximity problem, will a metal can effect a big toroid? I do not know, maybe, but I honestly think it wont make a difference, ferrite is not overly conductive, being in proximity to other metal probably wont have much of an effect on a 1:1 balun at all, 4:1 and other combinations it might have a slight de-tuning effect.I do not have any good reference books here to lookup to get a better answer than that, but the last thing you want is for that metal can to become an antenna and start radiating, so for that reason along, i put things like baluns and my remote tuner into plastic. I hate antenna debates because there is a lot of voodoo out there and fan boys ranting and raving about stuff that has no basis in reality.Long answer where answered nothing, other than to say, I would go with plastic out of precaution, but seeing tuners have metal cases and baluns in them, its probably not a problem. Try it and see what is what. The internals should be floating anyway and the case not part of the transmission line.Yes wind and build as per your image.

author: p.larner
author_rank: Frequent Contributor
timestamp: April 14, 2024, 11:08:42 pm
content: Thanks for your answer, I will try it in both a metal box ten a plastic one and compair, its just i have some eddystone type boxes but few plastic 73.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: April 15, 2024, 12:20:03 am
content: Quote from: p.larner on April 14, 2024, 11:08:42 pmI am a big fan of using what you got and seeing if it actually makes a difference. Ashar Farhan use tap washers in one of his home brew builds instead of iron powdered toriods, because they was what he had on hand, it worked perfectly acceptably as inductors. Almost impossible to replicate by anyone else, but you get the point. Often best wisdom is often nothing more than old wives tales passed down from one ham to another as if its true.I had a flick though the arrl books I have here and could not find any info that was usable. So there is that LOL If you are worried you could mount the toriod 10mm or so off the metal case using a block of something non conductive. That will reduce any capacitive coupling.

author: A.Z.
author_rank: Super Contributor
timestamp: April 15, 2024, 05:50:28 am
content: it isn't about the toroid, but about the windings and the couplinghttp://www.arrl.org/files/file/History/History%2520of%2520QST%2520Volume%25201%2520-%2520Technology/AntComp1-Lewallen(1).pdfusing a metal box we'll defeat the effect of the current BalUn due to parasitic coupling between the windings and the metal box, see it now ?And... no "old wives tale" here

author: shabaz
author_rank: Frequent Contributor
timestamp: April 15, 2024, 06:50:25 am
content: Could you highlight the relevant section in that 8-page doc if you don't mind?For sure, parasitic-created elements will impact more for some use cases, or if you do very unusual things (like strap the balun right against the conductive metalwork, without any gap/insulating shim/insulating standoff, etc.). Or if you didn't insulate the balanced end. But these are very solvable things, and once mentioned, it would be clear to a newcomer that the device should not be placed against metalwork, and that the balanced end needs insulating.If it were an unsolvable problem, then Minicircuits (and others) would obviously not sell baluns in metal enclosures. Didn't every high-end Hi-Fi radio receiver (folded steel enclosures) also contain them, for converting the 300 ohm balanced antenna input to 75 ohm?

author: vk4ffab
author_rank: Frequent Contributor
timestamp: April 15, 2024, 07:48:27 am
content: Quote from: A.Z. on April 15, 2024, 05:50:28 amI don't know AZ. I gave that document a quick skim over and it does not talk about cases for the balun or the effects of coupling. If i could be arsed one way or the other I could do the actual experiments here, but I doubt that adding a few puff is really going to make all that much difference. At least, not to the point of desegregating the choking and balancing ability.We have all used antenna that are out of balance. I ran portable for 2 years doing WWFF etc with a homebrew balunless dipole where the setup was invariably some level of inverted V often with dog legs, and then bought a sota beams linked dipole with balun and continued doing the same and it made no difference at all, when with it lashed to a tree beneath the canopy of a rain forest and other assorted stupiditiesI am still not convinced. I am not saying its not a fact, its just the proof offered so far is not compelling. If coupling was such a universal deal breaker just about every balanced tuner under the sun would not work in a metal box with caps and inductors millimeters away from the enclosure and toriods bolted to the chassis. Or other manufacturers that put baluns in metal cases. There is more to the story than don't do it and I still think its a be aware of the issues rather than a you cant type of thing.Happy to be proven wrong. Because I do not know for fact.

author: radiolistener
author_rank: Super Contributor
timestamp: April 15, 2024, 08:46:17 am
content: Quote from: p.larner on April 14, 2024, 08:54:38 pmyou can use metal box if you don't want to place it near antenna, but use connectors with ground isolated from metal box.Also note that small box is not a good choice, because you're needs to put your circuit at some distance from metal box in order to reduce capacitive coupling. So, a large box with a lot of space is better choice for that.Since you're planning to use it with ladder line it will be placed far away from antenna, so using metal box will be ok. I know old military antenna tuner which has metal shell and terminals for ladder line and it works very good.Here is example of antenna tuner in metal box, as you can see it uses terminals with isolators for symmetric or asymmetric antenna connection:

author: A.Z.
author_rank: Super Contributor
timestamp: April 15, 2024, 09:42:04 am
content: the point is, a metal box will need enough clearance to avoid undesired parasite coupling (same goes for tuners), so it's easier to use a non conductive material box for the balun, instead of making things more complex.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: April 15, 2024, 09:05:22 pm
content: Quote from: A.Z. on April 15, 2024, 09:42:04 amEven that, when i think about it, how much separation is enough and how big is the effect? Probably not a lot and the effect is small anyway. Think of a yagi or hex beam. Sure the balun is in a plastic box, but its securely attached to the boom which is made of metal. So 3mm of plastic is some separation, but it is still a capacitor. The bigger reason to use plastic outdoors is that its much easier to seal up and its non corrosive and low cost.And even then, there is more capacitance in the windings, inherent in coax itself, or twisted pair, that i think a few more pf really wont make much difference. as long as the self resonant frequency it stays above the 30mhz in the OP's case, it should not suffer any performance costs.That is something the OP can check himself with a VNA.

author: A.Z.
author_rank: Super Contributor
timestamp: April 15, 2024, 09:50:26 pm
content: think at a classic guanella current balun, some turns of coax wound over a toroidal core; some portion of that coax will have current flowing on the outer surface of the shield... see it ?I agree that it may be more a "belt and suspenders" approach, but if we can prevent issues, why not ?