[Elecraft] 4:1 balun

[Paul Christensen]

> "The down side of the 300 ohm twin lead folded dipole is that 300 ohm twin lead usually is made from small wire and not mechanically very strong, so it is not durable for fixed stations with varying weather conditions and the wire is too small for anything but low power.  With either the 300 ohm twin lead or a folded dipole fabricated from #14 or heavier conductors a 4:1 balun is needed to tune well with a 50 ohm output or to transition to coax.  Then it is about as good as a well made dipole."

I think the mechanical issues can be managed.  Generally, there's also less opportunity for water ingress than a coaxial line termination, unless more complex measures are taken for water-proofing.  I've got new respect for the folded dipole (FD).  The bandwidth of the FD is about 40% better between 2:1 VSWR points than a straight wire dipole.  This is due primarily to an effectively larger radiating conductor size (rather than end stub effects), wire size remaining constant.   For 80m-75m operating, the FD would be a good choice among the die-hard "I only use resonant antenna" ops.  For K2 or K3 owners, any common ratio current balun ratio would work reasonably well if equipped with the internal ATU.  If no ATU, then a 6:1 current balun would do the best job of transferring power into the line. 

The big drawback is that the FD won't work efficiently on even harmonics, even with a tuner at the shack end of the line.  But for mono-band performance, cost, ease of construction, it seems tough to beat.

Paul, W9AC