2.
VHF Simple-VEE-Rabbit-Ears (14 Feb 2011)VHF Simple-VEE-Rabbit-Ears (no matching network) analyzed using 4nec2.
Hi-VHF Band Optimum Whisker Length = 14.75 for Quarter-Inch-Copper-Tubing (QICT) with Feedpoint Gap = 0.75-in.
For 45-degree Angle, Horizontal Polarization Gain was equal to Vertical Polarization Gain across Hi-VHF Band.
Note: Even a 0.5-inch error in lengths of Rabbit Ears severely degraded SWR, although only minor impact on Raw Gain.
EDIT (10Sep2011): Added a "What-IF" exercise to illustrate the Raw Gain and SWR (if 300-ohms) from Ch2-13.
Note that SWR in Hi-VHF Band is four time higher than for 75-ohms, and becomes even more excessive
on lower freqs, as the Impedance becomes nearly all Capacitance (negative Reactance).
EDIT (16Jan2012): Added Circular Polarization Azimuthal Plots. Note that Right Circular = Left Circular
at 90-deg & 270-deg Azimuths, so there is very little suppression of Cross-Polarized (e.g. reflected Multipath) signals.
ERRATA (5Sep2014): Uploaded revised 4nec2 File with sin and cos functions reversed to match
Angle Definition in Comment description. Since all charts were for 45-degree Angle, they are NOT affected. |
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