160m INVERTED-L / 12m SpiderPole
( "ANY PORT IN A STORM" - ANTENNA )
I built the following antenna once, last minute, just before a CQWW 160m contest. I do not have the exact measurements anymore, but it must be adjusted for each different QTH anyway, so this information should be good for a start.
This is it, quick and dirty.
It won't work as well as our verticals on longer Spiderpoles but will work a lot better than ALL short commercial 160m vertical antennas.
Keep in mind that a couple of the lengths must be adjusted in the field, especially L2, so cut the wire a couple of meters longer and fold it back on itself. L3 (the vertical wire) is not critical since L2 is adjusted to compensate for variances in L3.
The capacitor will help raise the radiation resistance at the feed point. For permanent use, we would adjust the value of the capacitor as well as L2 until we optimized the match, but this is too difficult in the field on short outings. The 5kV rating of the capacitor should be good enough for 1kW. For 100w it can be about 1kV.
The RF choke is never a bad idea but not absolutely necessary.
(see "Choke D" on that page)