Will an ugly balun exhibit adverse effects if more coax is wound onto it than the recommended 18 - 21 feet?

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The antenna in this instance is a 40 Meter Delta Mono Loop that suggests using 22'-6" of 75-Ohm coax to transform the impedance of the feedline closer to the nominal 50-Ohms. Any reason why I shouldn't wind it all onto the choke balun coil form?

[Epilog]: I just received this email from W6NBC, who has an ARRL video on the design of ugly baluns.

"The Q of the choke at resonance is not critical in a choke balun. As a choke it is a broad band device that works by its impedance, which is high over a wide range of frequencies. Baluns do not have to be tailored to a band, though they can be of fewer turns if only used at the self-resonant frequency. Don't be afraid of supposedly "too many turns."



2 Answers 2


You can make the coil as long as you like without adverse effects. You will reach diminishing returns and waste cable if you go too far. For 40 m you do need a fair number of turns, maybe 10-20 turns on a 3 inch former, from memory.
Using all the RG-59 sounds like a sensible idea, then you can make one choke-matching device with a socket on the bottom and screw terminals on the top.

Keep winding the coil in one direction, on a former of some kind. A coil that's a bundle of wire doesn't work as well because of the capacitance between the start and the end of the coil.

The length of the 75 ohm matching section seems to be important, so keep that the same, whether it's coiled up or not. To be fair, if you're using a tuner, you probably don't need the matching section, but if it makes it work with no tuner, that's very neat.


Yes, it can. Ugly baluns aren't that broad-band by nature — in fact, they only really have a high impedance over a relatively modest frequency range, which is directly impacted by the number of turns (also the diameter and spacing).

Take for instance the data at the end of this post which contains VNA measurements of a few different shapes and sizes of baluns. The first two columns use the same diameter and turn spacing, but different numbers of turns. The one with 6 turns has a peak impedance of about 16k ohms at 24MHz, while the one with 12 turns is good for 42k ohms at 15MHz.

WF3T says that a choke is useful if it has a Zmag of >500 ohms, in which case the 6-turn one suffices for 14-30MHz and the 12-turn one for 7-28MHz. Personally I adhere to the theory that a choke should be >2000 ohms, especially if it's chiefly reactive. By that standard, the 6-turn balun is good from 21-27MHz and the 12-turn one from 12-19MHz, roughly.

Or see G3TXQ's choke data — the "air-cored" section on the graph represents ugly baluns, and again you can see the direct effect of number of turns. If your standard is Zmag > 500 then all of them are good over 2-3 octaves, but if you're shooting for a few thousand ohms then you need to design for your band, and G3TXQ makes arguments for why 500 ohms isn't such a great standard.

It's clear that if you made the thing 100 turns you would end up with a choking impedance that was quite high somewhere below 1MHz, but hardly any choking action at 7MHz, so there is such a thing as too much. Though by my math, 22'6" on a 4.25" form is only about 20 turns, which is actually quite reasonable for 40m.

If you're building a monoband antenna and you want to make an ugly balun, it makes sense to use one with its SRF right in the band of interest rather than just use however much coax you have. If you want a choke that works on several bands, something with ferrites is likely to be a better idea.


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