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You can use either a 1:1 balun or a choke balun at the feed point of the antenna or where the balanced part of the system meets the unbalanced part. The choke balun usually does the same thing as a regular 1:1 current balun but adds the high impedance path to the common mode currents too.
a 4:1 balun, for example, for the needed impedance transformations in an OCF HF dipole, but for most other balun applications, a simple coiled-coax 1:1 choke balun works very well.
Build a High Power 4:1 Guanella Current Balun RF Choke and Transformer Using 2 Cores. As with the 1:1 Balun, there’s plenty of online info on building 4:1 Baluns. I’ve seen and read many articles on baluns and there’s’ plenty of pretty variable advice out there.
(D2): 1:1 Guanella (W1JR) Choke Balun This choke balun consists of : 1.40m (4'7") of special Teflon-like Coax (DXW142), similar to RG-142; with 17 turns cross-wound (W1JR) onto an Amidon FT-240-43 or FT-240-31 toroid core.* 2x PL-259 with gold-plated contacts and Teflon insulation. * for 80 thru 10m, use "-43"; * for low bands (160/80/40) use ...
Łańcuch okrągłych rdzeni ferytowych zamontowanych na przewodzie koncentrycznym. Złącza, beczka i kabel koncentryczny oraz rdzenie ferrytowe pochodzą od sprawdzonych dostawców i są najwyższej jakości. Po złożeniu elementy są uszczelniane rurą termokurczliwą. Gotowy produkt jest testowany elektrycznie.
A very common use of a 4:1 voltage balun is in the construction of a coaxial-transmission-line-driven WINDOM antenna, which can be used without much more tuning required, on several bands. Here are some examples: Educational Paper: http://www.packetradio.com/windom.htm
The 1:1 choke "balun" is not actually a balun. It's function is to help eliminate rf currents from flowing on the outside of coaxial cable using the principle of choke action. Another "name" for it is the air choke.
