[TowerTalk] J-Pole Antenna on HF Bands

[Mark L.]

Don wrote
<< ...snip...Is the J-Pole limited to the higher frequencies, or can it be 
also be used in the HF spectrum? If so, will the formulas work at these 
lower frequencies? >>

Hi Don,
Yes, HF J-poles really work! I think of it as an end-fed vertical dipole. My 
first 10m & 20m antennas here, before I put up my tower, were homebrew wire 
j-poles pulled up into trees. They were and still are, effective DX 
antennas.
I posted design data for these right here in Towertalk so you may try to 
find that in the archives.
For my designs, I used bare, stranded, 18 gauge wire for the radiators, 
assuming a nominal velocity coefficient of 0.95, and 450 ohm, solid 
copper-clad ladder line for the matching stubs, assuming a velocity 
coefficient of 0.91. Following the formulas with a 1/2 wave radiator and a 
1/4 wave stub, taking care to mind the velocity coefficients above, got me 
real close. A little experimentation on the feed point and you can have a 
great vertical.
I also used coax choke baluns at the feedpoints. I made pigtails from RG-58 
that had a connector on one end, for the feedline, a choke balun coil, and a 
free end that gets soldered to the tap points on the matching stub.
To stow them, you can just wind 'em up on one of those orange electrical 
cord reels, rope and all.

It never occurred to me to create radials under them to try and improve 
their efficiency as per the current discussion. I had a lot of fun with them 
just by themselves. A single rope over a high tree branch (70' at my QTH) is 
all it takes to get on.

Have fun experimenting and good luck!

--...MARK_N1LO...--

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