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HiVHF 11-El Bi-Directional FD-Yagi - OPT (4 Jul 2016)Hi-VHF Bi-Directional [Push-Pull] Folded Dipole Yagi analyzed using 4nec2 after determining "best"
Dimensions using nikiml's Python Optimization Scripts.
Hi-VHF Raw Gain = 6.1 to 6.9 to 6.2 to 7.0 to 6.2 dBi and SWR (300-ohms) Under 1.3.
Not all that impressive...COMPARES to Gain of Hi-VHF 3-El FD-Yagi - OPT in each Direction:
http://imageevent.com/holl_ands/yagis/uhf3elfdyagiopt
Hi-VHF Raw Gain = 6.5 to 6.1 to 7.5 dBi, F/B & F/R Ratio Minimum = 13.3 dB (FAIR) and SWR under 2.1.
Essentially the SAME performance could have been provided by two Vertically Stacked 3-El FD-Yagi's,
going either to an A/B RF Selector Switch...or two Vertically Stacked 4-El FD-Yagi's going through
a properly designed Bandpass/Band-Reject Filters [e.g. JoinTenna or Tin Lee or Jan Jenka Channel
Injection Filters]. And even higher Gain with two Vertically Stacked 5 or 6-El FD-Yagis, with roughly
same total number of Elements instead....
There are very few articles re a Bi-Directional Yagi, other than the following, which indicates
about a 3 dB Gain LOSS between a standard Uni-Directional Yagi and a Bi-Directional Yagi,
or about the same as was found above:
http://www.jpier.org/PIERC/pierc44/08.13082204.pdf |
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