Single Band 40 Meter Dipole

Posted by Phil Hystad-3 on Jan 01, 2012; 5:14am
URL: http://elecraft.85.s1.nabble.com/Single-Band-40-Meter-Dipole-tp7141541.html

OK, lots of discussion on open wire feeders and other ideas so I thought I would throw out a question to soak up some of the Elecraft community knowledge and wisdom.

Given a 40-meter dipole antenna, up about 50 feet, what is the best feed configuration for single band usage to minimize loss and minimize common mode currents and radiation from the feed line?

I am thinking of building such an antenna and I would have no plans for using it on any other band but I would like to use it on the full spectrum of 40 meters with primary focus on the low end for CW.

My current idea is to cut the antenna for 7.1 MHz but I am not sure about the best plan to feed it.  I am thinking of 450 ohm window line (aka ladder line) to a 1:1 balun and the coax the rest of the way into the shack.  Or, how about 300 ohm twin lead into a 6:1 balun with coax the rest of the way into the shack?  Would this be a significant difference?  Or, some other combination?

Or, maybe a 1:1 balun right at the antenna feed point with coax the remaining distance to the shack?

Any comments or suggestions?

I am thinking of also raising up two other dipoles.  I have room to put up 80, 40, and 30 as separate dipole antennas -- it is actually a little bit more awkward to do a fan dipole so I am leaning on not doing that.

73, phil, K7PEH

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