[ADXA] I made a 40m Dipole

[Stan Stockton]

Thought I would share this with you.  I wanted to put up a flat dipole and the space between the two towers was not enough.  I didn’t want other ropes taking ends down close to the two towers, one of which is shunt fed for 80 and the other for 160.  

At each end there is a six foot piece of 1/2” aluminum tubing.  The dipole is 47 feet long and connects to that tubing in the center.  From each end of the 6 foot pieces of tubing a wire comes back and is soldered to the main wire at 149 inches out from the center (or 133 inches back from the end.

You’ll have to blow the picture up to see the dipole.  This is 2/3 the length of a normal dipole.  It is a perfect match to 50 ohm coax.  A flat, full sized one will never be better than 1.5-1 without some matching.  

There are lots of applications for this style for the low bands including sloping dipoles (about 88 feet for an 80m dipole) shorter verticals for a 4 Square, etc.

Unfortunately this thing doesn’t model too well even with NEC-4.  It showed resonance about 150 kHz lower than it really turned out to be.  NEC-2 showed resonance 535 kHz low!

The software was good to determine what to change to move it however much it needed to be moved after I put it up.

73…Stan, ZF9CW (Sorry, it’s 75 degrees here) 😀



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