Month: December 2016

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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Classic G3TXQ Balun / Choke Article

Excellent technical reference article by Steve G3TXQ:

choke_impedances_g3txq

Amateur Radio (G3TXQ) – Common-mode chokes

The above chart presents the results of impedance measurements made on a variety of common-mode choke implementations across the frequency range 1MHz to 30MHz. Amateur frequency allocations are indicated approximately by the vertical grey bands. Continue reading Classic G3TXQ Balun / Choke Article

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Classic N6LF Radiation Resistance Article Series

rr-study-appendix-a-1 pdf

rr-study-appendix-b-v2-1 pdf

rr-study-appendix-c-rev-1-1 pdf

rr-study-appendix-d-1 pdf

   rr_study_n6lf

 

from http://from http://rudys.typepad.com/

 

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Non-Resonant 25 ft Vertical with Metal Fence Counterpoise – 7 Bands

With the interest in 43 foot untuned verticals, and some of the less than accurate claims being made, I thought I’d share the results of a 25 foot untuned vertical antenna I developed a few years ago. Hopefully, I can shed some more light on its practical use, as well as show how to gain a bit more performance.

Continue reading Non-Resonant 25 ft Vertical with Metal Fence Counterpoise – 7 Bands

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