notes:
Co-linear/Phased
http://www.w6kan.com/k3mrg2.html
http://iacantennas.com/docs/Double-Bazooka-Phased-Array.pdf
http://www.sage-american.com/SK/cebik/a10/scv/bc40ab.html
http://ac0c.com/attachments/40m_parasitic_to_phased.pdf
Moxon
http://www.iw5edi.com/wp-content/uploads/2013/06/40-Meter-Mini-MOXON-Beam-Antenna.pdf
http://www.moxonantennaproject.com/IK0GDH/IK0GDH.htm
http://www.moxonantennaproject.com/w1zymoxon.htm
http://www.optibeam.info/index.php?article_id=85&clang=1
Quad/loop
http://n4jte.blogspot.com/2006/10/2-element-40-meter-reversable-quad.html
http://www.hamuniverse.com/na4lquagibeam.html
Yagi/dipole
https://www.dxengineering.com/parts/csh-d4
http://www.jkantennas.com/jk403.html
http://www.rssl.lk/40-meters-3-element-wire-yagi-by-ve3vn/
http://amfone.net/Amforum/index.php?topic=19385.0
http://lists.contesting.com/_towertalk/1997-12/msg00178.html
http://ve3vn.blogspot.it/2014/05/40-meters-3-element-wire-yagi.html
http://ve3vn.blogspot.it/2014/12/40-meters-4-element-wire-yagi.html
http://lists.contesting.com/_towertalk/1998-05/msg00610.html
http://egpreston.com/40mbeam.txt
http://www.dxzone.com/catalog/Antennas/40M/40_meter_Yagi_Antennas/
(3-6-9) http://radio.n0gw.net/radio05.pdf