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Author Topic: 9:1 Balun (Dare I Ask)  (Read 24401 times)
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n3lrx
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« Reply #25 on: November 08, 2013, 10:15:26 PM »

Actually Steve, all the spark box needs is the plastic supporting ribs on the inductor to be replaced. The glue is probably dried out enough that they might just pop off. No wires are broken, no bent or zorched caps. I just never put the time into it because I couldn't use it. But if I pull it apart and replaced the supporting ribs it would be a fine 250 Watt tuna for someone. Maybe I'll make that a winter project. I can learn some restoration skills. Then donate it to an aspiring AMer with an Apache or something.

Well Jim, I actually had the same problem with not being able to read my cross needle on the tuner and I replaced the bulb today with a white LED wow! I can see. It illuminates the entire back panel rather than just a blob of yellowy light in the center and dark corners the whole meter lights up. As the home decorators like to say, 'It really makes it pop!" Wink
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Randy, N3LRX (Yellrx)
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« Reply #26 on: November 14, 2013, 04:02:49 PM »

Just practicing making baluns.. Ya think it will work at a KW? (J/K)


* DSC00324.JPG (503.93 KB, 4608x3456 - viewed 451 times.)
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Randy, N3LRX (Yellrx)
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« Reply #27 on: November 14, 2013, 05:12:36 PM »

Just practicing making baluns.. Ya think it will work at a KW? (J/K)

Without looking at the jpg, and at distance. The answer is could be no. The Lou McCoy Ultimate Transmatch used three (3) T200-2 cores stacked. And from 30 years plus usage on mine, 350 watts carrier AM is close to the max for olde buzzard transmissions.

So how you measure a KW might come into play. The 1976 ARRL handbook said 2000 watts, but that is PEP for the three stacked cores.

YMMV

Craig,
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n3lrx
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« Reply #28 on: November 14, 2013, 05:24:51 PM »

Yeah, that's just a joke, a practice balun. I have no intention of running a Kw through it.  I found a T200-2 and wrapped up some 12 ga. solid house wire for fun.

I'll be ordering a bunch of T200-2 cores soon. I'm going to wrap about 12 of them with 12 ga. stranded until I can't wrap anymore. I've got about 50 feet of the 12 ga. wire in black and red (25 ft. each spool) so we'll see what I can do with it. That should be more than enough for my transmitter.

I've also got the aluminum project box and the perf board. I just need to order the ceramic feed throughs for the balanced line an the SO-239 for the coass. I'll be ordering several SO-239's because I have yet to finish my diode detector.
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Randy, N3LRX (Yellrx)
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« Reply #29 on: November 14, 2013, 06:28:55 PM »

OK, both my 74 and 78 ARRL handbooks say 10 bi-filler turns.  My 88 ARRL handbook has no windings set in text. So I'll stick with the 10 turns since it's recommended in 2 books over the one. Mind you the 74 and 78 go into much more detail in a quite few applications than the 88 does, and the 88 is a bigger book! I'll stick to the older published books for most of my future research. I think I can actually learn something from them.

I used to have practically every ARRL Handbook ever published up to 1996 but I sold most of them off before I moved to California, and a few more I had in storage when I moved to Massachusetts  I regret that now. I've only managed to procure the 74, 78 and 88 for my collection. I forgot I had the older ones. I just had my 88 on the shelf the older ones I inherited when a friend passed away. They were on the shelf in a box. Every time I go to a hamfest the older ones are always on my pickup list for years I don't have. (If they aren't outrageously priced.) I"ll also be looking for the ARRL Antenna Book (Which I also sold off) at the local upcoming spring hamfest. Moar Books!

I'll be using the Big Bacon Balun modified with 12 cores instead of 8, and 12ga. stranded instead of combined 16ga stranded. As Frank put it, for high powah you can never have too many cores!
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Randy, N3LRX (Yellrx)
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« Reply #30 on: November 14, 2013, 07:31:03 PM »

Nothing in those ARRL HB regarding baluns that can't be found in the Web. In fact, you'll find much more info on the Web. Save your $$.
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n3lrx
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« Reply #31 on: November 15, 2013, 03:06:51 PM »

Well, I went to the hardware store today, bought a bunch of nuts, bolts and washers for my balun and I forgot one freaking $0.10  nut. I should have just bought a handful but hindsight is 20/20. I'm gonna do that on my next trip there. I'll just buy a handful of nuts, washers and bolts. I don't have 10-24 or 10-32s in my inventory and they can come in handy.
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Randy, N3LRX (Yellrx)
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« Reply #32 on: December 09, 2013, 03:23:57 PM »

Well, I got most of my balun built. Still waiting on the SO-239 and the feed through posts for the balanced line.

I got my cores in this morning and went to work. Here's what I've got so far.



This damn thing is heavy, I bet it weighs 5 lbs or more, It's got 12 T200-2 cores  in it.
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Randy, N3LRX (Yellrx)
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« Reply #33 on: December 09, 2013, 06:52:21 PM »

If it's not too late to back up and go ahead, I'd like to see  3M glass cloth tape run through the center of each stack of toroids, completely enclosing them.  I was too impecunious to do that when I made my first one, but I used plumbers teflon tape for the same purpose, then tacked it down with a bit of black poly tape.
On my original balun years ago in my Ultimate Transmatch, bifilar wound on a three T-200 stack, I have had arcs to the core, and I found some one-inch wide teflon tape that cured it, and looked very techy as well.
Other than that, it's a handsome unit.
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n3lrx
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« Reply #34 on: December 09, 2013, 07:02:32 PM »

I can't find my glass tape Sad I know I've got a roll around here somewhere and I've torn this place apart looking for it. Sad  It sat in the same location for years because I had no use for it. Now that I have a use for it I can't find it. Go figure. It's 12ga. Teflon wire so hopefully that makes a difference.

Incidentally, I did get a note from UPS my parts did ship today. So I'll have them around the 11th. Grin
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Randy, N3LRX (Yellrx)
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« Reply #35 on: December 09, 2013, 07:45:28 PM »

That's a really cojones-style balun there! Looking at your product, which is very impressive, the only comment would be to employ more insulation against high voltage.

That is what blew up the old '3KW' balun here.
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n3lrx
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« Reply #36 on: December 09, 2013, 11:03:44 PM »

Thanks for the compliment. It was really quite simple once I had it explained to me in simple terms for my simple brain. (What's left of it.)

Hopefully I won't have any problems with it arcing within itself. It's Teflon wire, rated at 600 volts, which is the highest I could find.  I actually was going to use 10ga.  but opted for the 12ga. because I couldn't find enough 10ga. Teflon wire in two colors at a reasonable price. I found 12ga. in 12' x 2 (24 Feet total),  in 2 colors for $20 shipped, so I bought it.

It's certainly built like a brick outhouse. It's probably capable of handling much more than my transmitter can throw at it, and will probably work with any antenna within reason. But it was built that way intentionally.

If an idiot like me can do it you can too!

Now all I have to do is set up a station at my moms house and try it out! I certainly can't use it in this apartment.
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Randy, N3LRX (Yellrx)
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« Reply #37 on: December 10, 2013, 01:30:20 PM »

Dammit, It figures, now that I have finished wrapping my coil, wire trimmed. and the ends on it, I find my glass tape. Go figure. I don't think I can unwind it and get it right now that the wires are trimmed to length. Cry
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Randy, N3LRX (Yellrx)
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« Reply #38 on: December 10, 2013, 02:04:22 PM »

Nope. The ends are trimmed and the eyelets soldered on I'd have to cut them off and re-wrap it. I can't fit the eyelets through the cores with the wire wrapped. I hate how Murphy's law works. If I cut the eyelets off I won't have enough wire left once re-wrapped.
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Randy, N3LRX (Yellrx)
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« Reply #39 on: December 10, 2013, 02:24:54 PM »

With my current design, with the lack of the HV tape, do you think I will have arcing problems at 1-1.5 Kw? I certainly won't be running any more power because the transmitter has a hard limit at 1.5 Kw peak. Anything beyond that causes nasty negative peaks so says Bruce. So 400 W carrier (MAX) 1.5 Kw PEP (MAX)

I don't plan on loading up lawn furniture I'll use a respectable antenna with it.
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Randy, N3LRX (Yellrx)
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« Reply #40 on: December 10, 2013, 03:24:49 PM »

It will either arc or it won't.  Your 600 volt wire probably won't arc at 601 volts.  And much depends on whatever complex impedance your antenna and line combination presents to the balun input terminals.
The advantage of being a real homebrew-savvy radio amateur, instead of one of those appliance operators in their disco shirts and shiny platform shoes, is that you can rebuild it if it smokes.  And better next time.  Put that 3M tape someplace safe, but not as safe as last time.
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n3lrx
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« Reply #41 on: December 11, 2013, 04:42:03 PM »

OK, here she is.. http://qsl.net/n3lrx/balun-how-to-markup.html I documented every step I took to build a 4:1 balun. Feel free to comment for any corrections.

Thanks to all those that helped.
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Randy, N3LRX (Yellrx)
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