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Ham Talk Live! Episode 248 - Building the Big Ugly Balun

Discussion in 'Amateur Radio News' started by WB9VPG, Feb 24, 2021.

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  1. WB9VPG

    WB9VPG XML Subscriber QRZ Page

    The "big ugly" might be a famous 22 ounce hamburger in Indiana, but this week on Ham Talk Live! we're talking big ugly baluns! John Portune, W6NBC will be on the show to take your questions about building an ugly (coiled coax) balun and why they are useful.

    Tune into Ham Talk Live! Thursday night at 9 pm EST (Friday 0200Z) by going to hamtalklive.com. When the audio player indicates LIVE, just hit the play button!

    If you miss the show live, you can listen on demand anytime also at hamtalklive.com; or a podcast version is on nearly all podcast sites a few minutes after the live show is over. Some sites include Apple Podcasts, Google Podcasts, Spotify, SoundCloud, Stitcher, Spreaker, TuneIn, Vurbl, and iHeart Podcasts; and it's also available on YouTube.

    A replay is also broadcast on WTWW 5085 AM shortwave near Nashville, TN on Saturday nights at approximately 3:30 pm Eastern.

    Be sure to CALL in with your questions and comments by calling 859-982-7373 live during the call-in segment of the show. You can also tweet your questions before or during the show to @HamTalkLive.

    bigugly.jpg w6nbc.jpg
     
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  2. K2WPM

    K2WPM XML Subscriber QRZ Page

    Thought this was very interesting, thanks for the article John.
    I also really liked John's experiments with ladder line. w6nbc.com/articles/openwireline.pdf
    Be aware of the QRZ controversy over John's article however ... the thread is up to six pages!
    But coax-wound baluns aren't going anywhere; just search the antenna forum using the word "ugly."
    For ugly balun.
     
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  3. KM1H

    KM1H Ham Member QRZ Page

    Id love to see a NanoVNA (or any other plot) of that thing as they have a reputation of being very narrowband.

    Carl
     
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  4. W1YW

    W1YW Ham Member QRZ Page

    My preference would be to see this coil balun on CPVC rather than PVC, at least at HF.

    Nowadays one can VNA-measure the insertion loss of such coil baluns by a S12 'thru' normalized via a wee short length of hardline for the 'normalized' length. Anyone know its insertion loss at various freqs:)?

    Anyway, the objective of the Big and Ugly is to get folks to build stuff, always a welcome and valuable opportunity.

    I always enjoy frying concatenated choke baluns myself;-) Many years ago, my neighbor called the cops because such ferrite choke baluns are built into PVC pipe and look like pipe bombs... I asked the cop: what was I supposed to be blowing up... a bush in my backyard?
     
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  5. K6MIT

    K6MIT Ham Member QRZ Page

    ITS NOT A BALUN why do people keep calling these a balun ? a balun matches two different impadances.
    all this is is a rf choke..doesnt match anything...just stops rf from traveling on the shield of the coax...
    and even then, its only effective on the design freq of the choke and useless on all other freqs.
     
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  6. PA0MHS

    PA0MHS Ham Member QRZ Page

    Wrong. A balun matches a balanced entity to an unbalanced entity. And that's exactly what this thing can do. And technically speaking, this is a transmission line transformer with a 1:1 ratio. And if you ground one end, the other end becomes symmetrical with respect to ground. And it presents a high impedance to common mode currents flowing through both the center conductor and the shield.
     
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  7. W1YW

    W1YW Ham Member QRZ Page

    No, a balun interfaces a balanced load with an unbalanced load.
     
    Last edited: Feb 25, 2021
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  8. K5SOP

    K5SOP Ham Member QRZ Page

    Balun: A device or method used to match balanced people to unbalanced people.
     
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  9. KA1VT

    KA1VT XML Subscriber QRZ Page

    Called a Choke but also referred to as an Ugly Balun, it works and that is what is important. I made one with terminals for my G5RV and one for the OCF antennas I run. See below. Keep them away from metal, and I supported mine with the loops shown onto a wooden support. I used 2" wide electrical tape - and used 23 feet of coax. ugly choke.JPG
     
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  10. KZ5R

    KZ5R Subscriber QRZ Page

    New Model 1115.jpg 1-1 Compare Air Coax - 1115u.jpg 1115u v Air Wound Coax.jpg

    These three scans are for Carl who requested a scan of an air wound balun. The second graph compares SWR, Transformation and return loss to a toroid wound balun and the bottom graph is choking impedance. The core used in this last graph has since been updated and you can see the choking it now provides in the first scan. Hope this helps.

    Bob, Balun Designs
     
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  11. KM1H

    KM1H Ham Member QRZ Page

    Thanks Bob and that confirms how poor the ugly coax balun really is and has been long suspected for decades.
    They can be made to do a fair job on a 14-30 Mhz yagi for instance but does require some test equipment and patience.

    I got involved with them in the 80's when dealing with owner problems with various Mosley yagis which seemed to be exceptional TVI generators as built.

    Carl
     
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  12. W1YW

    W1YW Ham Member QRZ Page

    Nice, but---

    What is REALLY important is the insertion loss. A -30 dB return loss is a trivial improvement in mismatch loss from, say -20 dB.

    If you want to know where you are losing POWER (and how much) in the device, you must know the insertion loss, and separately, the mismatch loss.

    You can certainly figure out the (trivial) mismatch loss from the return loss. But the insertion loss is far more important in the overall power loss to this device.

    You can get the insertion loss by S12 (that is, the 2 ports) thru a short piece of hardline in-line, normalizing, and then replacing with the device in-line. The second curve you see, to good approximation, will be the insertion loss as a function of frequency for the device.


    Most people have no idea what a 'return loss' is, and assume that going from -20 to -30 dB return loss means its "10 dB better!".

    Wrong, It means it is a trivial amount better because you have slightly decreased the mismatch loss.

    If your device has an insertion loss of, say 2-3dB (ugh)! chances are you are generating a fair amount of heat. At 1500 watts there is the potential for fire: over 700 watts worth of heat in a small volume. So understanding the INSERTION LOSS is key not only for PERFORMANCE, but also for SAFETY.

    The 'line isolator' (looks like a pipe bomb but isn't)I referred to was lossy at MF and crisped up nicely. Nice, dripping plastic. Buh-bye line isolator! It had a 2 dB insertion loss on 160m, as measured on an HP VNA.

    I shudda known better (this was many years ago), and am passing this on.

    :)

    73
    Chip W1YW
     
    Last edited: Feb 25, 2021
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  13. KM1H

    KM1H Ham Member QRZ Page

    Return Loss has historically been an engineering term used in labs, formal specifications, publications and the like. The CATV industry has used it as long as I can remember which goes back to the 70's.
    Since it is reported in dB it is so much easier to integrate it into other functions and test equipment.

    Hams seem to be stuck in the VSWR world for some reason and many still dont even understand that much less own things that measure it accurately

    Here is a chart to make it easier.

    https://www.minicircuits.com/app/DG03-111.pdf

    I wont get into dBmV and dBm(W) today:eek:

    Carl
     
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  14. W1YW

    W1YW Ham Member QRZ Page

    I can't tell you how many times I have seen people say that 'return loss' is 'insertion loss'.....:-(
     
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  15. K4YNZ

    K4YNZ Ham Member QRZ Page

    RF Choke, transformer or balun will have a calculated bandwidth. The simple loop RF Choke was standard for 28-14 mHz antenna. Did not see them on say 6 meters. Our standard, in 1977, was simple. SWR OK? Mic bite you? Neighbors complaining of TVI? If there was a lot of loss at the antenna who knew? Unless you had a failure. Now today we have different challenges. We want our internet, PC, and associated sound cards and audio chain to be RF free. My Drake's did not have DC ground loop issues either.
    Now we did run RTTY with a VIC 20.

    My two cents? The typical radio operator, today, wants multi-band antenna. In some cases 6-160 meters. Math says this is a challenge. In 1977 I used resonant antenna only. Tri band bean for 10-15-20 meters SSB. Trap dipole for 40/75 meters SSB. If I wanted to operate CW I had to use the Dentron tuner. The reason was loss and heat if you went down to the CW end.
    Now today's radio operators are too cool. We have inexpensive Vector Network Analysis tools. First time I swept microwaves we used at least 100 pounds of HP gear costing a small fortune! Open, short, an Wed 50 ohm line sweep. Measure feed line insertion loss. Then a system sweep. A way of life for 30 years.

    1977 I had a Bird watt meter, grid-dip meter and a noise bridge. Now I have a MFJ analyzer, A LP 1000 watt meter that will give me SWR, power, return loss and X,Y and impedance! You have to do the math and measure the real world and compare.

    Oh, Chip. The fractal antenna thing. I'm still trying to get my mind around that. OK Weak in geometry.
     
    Last edited: Feb 26, 2021
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