Pictured is a 4:1 balun. It is also the same as that used on the M0CVO HW range of antennas. It will take full legal limit (UK) of 400 Watts RF power easily and is used to convert a 200ohm impedance to the 50ohm required by most transceivers of today. Ideal for use when constructing antennas such as an Off Centre Fed Dipole, Windom or Delta Loop. Use this as your feedpoint and feed with 50ohm coaxial cable.
Also available is a 1:1 balun. This will also handle up to 400 Watts of RF power and is used to feed a balanced antenna, such as a centre fed dipole with an unbalanced feeder, such as coaxial cable. It will reduce static on the feedline, thus reducing unwanted noise and prevent RFI being fed back into the shack.
UNUNs used to match an unbalanced antenna such as an end fed long wire or vertical antenna to an unbalanced feeder (coaxial cable). The 9:1 UNUN is for a long wire antenna and the 4:1 (Magituner) is for a shorter wire vertical that could be mounted on a fishing pole (fibre glass). The Magituner (B) is for use with a CB vertical to convert it for HF use.