Verticals and Inverted-Ls for the Low Bands – Horizontal Antennas for High Bands

Ever wonder why successful DX-seeking stations so often use vertically polarized Verticals or Inverted-Ls on those lower bands?  And why horizontal dipole-type antennas are most often seen for use on the higher shortwave bands?  Even loop designs, intended for DX chasing on these lower bands, most often employ vertical polarization.

There’s good solid technical reason for this old adage:

If you can’t get a horizontal antenna up around 3/8 wavelength or higher, then use a vertically polarized antenna.

Continue reading Verticals and Inverted-Ls for the Low Bands – Horizontal Antennas for High Bands

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Current Flow Fundamentals for an “End-Fed” Antenna – part 2

Part 2 – A 40 Meter EFHW with a “Radiator” wire and various length “Coax-as-Counterpoise” wires is analyzed – We will see that the common-mode current is almost always LARGER on the coax shield some distance away from the feedpoint, which is why the “counterpoise” radiates and is called “the other half of the antenna”.

It is sometimes said that common mode current flow on the coax shield of an “End-Fed” antenna system is everywhere low,  simply because the feedpoint current is relatively low.  This is claimed even for systems with no “counterpoise”.  In this article we will see that this is not true.

…charge conservation is the principle that electric charge can neither be created nor destroyed.”*

As shown in Part 1, from this perfectly reasonable principle we now know that there are NO 1-Terminal RF power sources!

nooneterminalacsources2 Terminals – YES!            1 Terminal – NO!

Continue reading Current Flow Fundamentals for an “End-Fed” Antenna – part 2

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End/Base-Fed Inverted-L, 45 ft version, Elevation and Azimuth Radiation Plots

Below are presented the results of EZNec modeling of a 45 ft long End/Base-Fed Inverted-L, 23 ft high and 22 ft across.  Elevation patterns and Azimuth patterns at the peak of low angle radiation are plotted for all ham bands 80 Meters through 6 Meters.

For modeling purposes, a multi-connection distributed grounded counterpoise is used. This empirical structure provides a reasonable broadband counterpoise over the frequency range of interest.

inv_l-model-pic

Continue reading End/Base-Fed Inverted-L, 45 ft version, Elevation and Azimuth Radiation Plots

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End/Base-Fed Inverted-L, 90 ft version, Elevation and Azimuth Radiation Plots

Below are presented the results of EZNec modeling of a 90 ft long End/Base-Fed Inverted-L, 45 ft high and 45 ft across. Elevation patterns and Azimuth patterns at the peak of low angle radiation are plotted for all ham bands 160 Meters through 6 Meters.

For modeling purposes, a multi-connection distributed grounded counterpoise is used. This empirical structure provides a reasonable broadband counterpoise over the frequency range of interest.

inv_l-model-pic Continue reading End/Base-Fed Inverted-L, 90 ft version, Elevation and Azimuth Radiation Plots

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