Hi-VHF 4-Element Yagi Antennas - based on Dave47's antenna, designed per K7MEM (DL6WU) on-line calculator: http://www.avsforum.com/avs-vb/showthread.php?p=13785312 http://www.avsforum.com/avs-vb/showthread.php?p=16552404
Compares 300-ohm Folded Dipole Yagi (Dave47's) to 75-ohm non-folded Yagi: essentially the same performance. Same Boom Lengths=58.7-in.
Net Gain only covers Ch8 and Ch9. Raw Gain extends throughout Ch10, but with excessive SWR. So these 4-Element Yagis have LESS bandwidth than similar 8-Element Yagis.
NEC simulation normally does NOT include the boom. When constructing a real antenna, a "Boom Correction" is added to the length of each element to compensate for the additional loading from the metal in the boom, but ONLY when using METAL boom construction.
CLICK ON IMAGE (and click again) TO SEE HIGHER REZ.
Date(s): 30May2009. Album by holl_ands. 1 - 9 of 9 Total. 4754 Visits.
enlarge 0KB, 1024x747 1 Hi-VHF 4-El K7MEM Folded Dipole Yagi vs "Stick Dipole" Yagi: Essentially no difference.
Although Raw Gain covers Ch7-10, Net Gain is best only over Ch8-9. Rapidly falling Net Gain across Ch10 can cause reception problems.