(work in progress)
An “end’fed” is kind of a misnomer – there is ALWAYS a counterpoise.
For resonant antennas, the counterpoise requirement in minimal. Often the feedline is used as a sort of unintended counterpoise – not a very good idea because of the problems that can happen when the feedline is part of the antenna, like noise pickup, inefficiency, pattern skew, and RF-Bitey-Mic reasons.
A better setup is to use the 0.05 wavelength (or thereabouts) formal counterpoise that is recommended in articles like Steve AA5TB’s. These are generally used with the 49:1 (or thereabouts) transformer, and often has the “cross-over” winding”. This transformer brings the resonant Z of around 2.5 K ohms down to 50 ohms.
Non-resonant “end-feds” differ in that they are more along the lines of OCFD or non-resonant vertical / inverted-L / slopper. Again, some designs rely on the coax feedline as the unintended counterpoise – also not a very good idea for the same noise pickup, inefficiency, pattern skew and RF-bitey-mic reasons above.
The differences in definition get kinda hazy, but generally a more substantial counterpoise (longer second radiator wire, or actual radial system) is needed to work with the lower ratio transformer (Unun) of 4:1 or 9:1. These are usually wound bi- or tri-fillar. This transformer moderates the high SWR to lower levels for less coax loss, and to levels that are easier to match with auto-tuners.
From “80 Meters and Up – Portable Base Matching Unit for 42 to 48 Foot Verticals and Inverted-Ls – Medium Power Version” ===> http://vtenn.com/Blog/?p=1570
Either system can be used /P in the field without as much concern (except for poor efficiency) of the negative effects of using the coax feedline as the counterpoise. After all, there’s no house wiring around to couple to, no noisy wall-wart power supplies to pick up, and power levels are often low so you don’t get too big a RF hole in your lip ……Note however, that efficiency suffers when the counterpoint (coax, radio and wiring, etc…) is in proximity to ground. And it suffers severely on the lower band if a true radial system is not used.
There’s a lot of stuff out there that kinda sorta “works”, and there’s plenty of bad info out there as well so it’s always good to go back to basic antenna principles for guidance!!! It’s often the difference between kind sorta getting these often poorly defined thingies merely “working”, and using them with proper counterpoise / radials so that they work efficiently and correctly
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