Current Flow Fundamentals for an “End-Fed” Antenna – part 1

Part 1 – A simple transmitter, transmission line, and an “End-Fed” antenna WITHOUT a formal “Counterpoise” – We will see why common-mode current must ALWAYS flow on the coax shield.

End-Fed Antennas have been around since the good ‘ol days and were once most popular.  Yet for some reason, much discord still exists regarding the “counterpoise” – what its behavior is, or if one is even needed.  Not all that surprising since the term “counterpoise” doesn’t seem to have a firm definition.  Hopefully, we can figure out what’s going on despite the semantics, and deal only with easy to understand basic principles.

Principles like this from basic physics:

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

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Current Flow Fundamentals for an “End-Fed” Antenna – part 3

Part 3 – We place various devices at the feedpoint of an “End-Fed” antenna without a formal “Counterpoise” – We will see why the SAME common-mode current must ALWAYS flow on the coax shield just as in Part 1.

The typical “end-fed” generally has an impedance greatly different from 50 ohms, so it is rarely fed directly with coax, as losses on the transmission line will be undesirably high for lengths of coax greater than a few 10’s of meters.

Note the high loss on several bands when a 42 ft “end-fed” is directly fed with 50 ft of RG8x coax (yellow bars)* ===>

cableloss_unun-vs_direct_feed Continue reading Current Flow Fundamentals for an “End-Fed” Antenna – part 3

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Some Early Tubes and Circuits

Some early tubes and radio circuits from Radio News and BELL Telephone Laboratories.

searlytubes1926 1926_Radio-News__tubes-and-there-uses

higheffpa_1928_articlecover1936_BELL_Labs__high-efficiency-power-amp-for-modulating

fm_receiver  1940_Radio_News__design-notes-on-a-fm-receptor

 

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Simple Ultra Wideband (UWB) Antenna – 200 MHz Bandwidth

In the course of my career as an EE specializing in Ultra Wideband radio, radar, and antenna hardware, the need often arises for a useful and easy to reproduce UWB antenna.

dualplatepic_200-400_mhz Continue reading Simple Ultra Wideband (UWB) Antenna – 200 MHz Bandwidth

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Classic Collection of Early James Millen

Here is a collection of some of James Millen’s early work in radio communication techniques.

radio-design-guide-1935-cover

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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.

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Conformal Dual Patch Antenna for a Rocket

An interesting pro-bono project: design a conformal antenna for a university class-project rocket’s data link.

testrocket

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