ANTENNA RADIATION EFFICIENCY
The single most important thing for any antenna to radiate effectively is that voltage and current on the antenna be IN PHASE at the feedpoint. This article discusses reality of what is needed for an antenna to radiate effectively.
Understanding Resistance, Reactance, Resonance and Impedance
The relationship of Resistance, Reactance, Resonance, and Impedance is confusing to many, partly because of the use of the term "resistance" to mean two entirely different things, and partly because of the "folk lore" surrounding these terms that is contrary to well-established and proven Engineering practices and theory.
This article delves into these as they apply to antennas, their design, and their performance.
EZNEC Pro V7 Wires and Source data for Fan Dipole: EZNEC Wires and Sources
Antenna Orientation Tool (This is an Excel file that allows you to design to fit antennas to your space.)
This is the link to the updated NVIS PATH ANALYSIS TOOL with instructions. I created it to allow a single point view of all of the significant parameters involved in NVIS communications planning. This tool takes VOACAP outputs for multiple SSN and produces graphs of MUF, Take-off angle, Virtual Height, and Signal-to-Noise Ratio for each of five Sunspot Numbers on the date specified. It is useful for wide area emergency communications planning for long periods with widely differing Sunspot Numbers.
It is suggested that you run the tool for a minimum of 4 dates separated by 3 months each. I like to use the sumer and winter Solstices (~ 21 June and 21 December) and choose the same day of the month in March and September, even though that may miss the Equinox by a day.
Note that both VOACAP and the tool support multiple SSN on the same date -- so only one run per season is required. That allows you to decide to run monthly predictions with only 12 runs, should you so desire.
NVIS Path Analysis Tool
Near Vertical Incidence Skywave Presentation
This is a still image version of my fully animated NVIS presentation.
It contains propagation graphs (produced using the NVIS Path Analysis tool below), with visibility of the "WHY" for each time period. I have included several NVIS antenna designs -- including one that looked really good in an old version of EZNEC, but not in the latest EZNEC Pro. (See slide 46: "3.8 / 7.2 MHz “Double Vee” Dipole").
The other antenna designs shown have been peer reviewed and verified by a couple of experts in antenna design.
NOTE: The fully animated video of this presentation (with audio) is in production, and will be posted here soon. It answers several questions not well addressed as "bullets".