The N2CX  HALFER
...a Simple Portable QRP Antenna

NOTE ... N2CX wrote an article for 72 newsletter sometime back in 1997 or 1998 in which he discussed the theory and operating characteristics of End-Fed Half-Wave Antennas.  Click here to read this article.

What is a Halfer?

The Halfer is a “minimalist” End-Fed Half-Wave Antenna for the 7 or 10 MHZ amateur bands intended to provide a very simple to erect yet effective portable QRP antenna.  It features are:

·  Light weight - about 7 ounces  
·  Small Size - fits in a quart zip-lock bag  
·  Efficient - same as a half-wave center fed dipole  
·  Effective - can be configured for local or DX operation  
·  Simple - single antenna wire and single counterpoise wire  

·  67 foot insulated antenna wire  
·  34 foot counterpoise  
·  Three antenna insulators  
·  Copy of  End-Fed Half-Wave Antenna article from 72 newsletter

As described in the accompanying article, the half-wave end-fed antenna can be as effective as the common center fed dipole antenna yet is simpler to put up and  much easier to carry along  for portable operation.  This  information sheet, in conjunction with the included article, will provide all you need to know to erect and use the Halfer.

First you must decide whether you want to use the Halfer on 40 or 30 meters.  It is already cut for 40 meters.  For 30, both wires must be shortened.  The half wave wire should be about 47 feet and the quarter-wave counterpoise wire should be cut to about 23-1/2 feet.  The lengths for both 40 and 30 meters are slightly longer than an electrical half wavelength.  This is intentional for several reasons.  If the wires need to be adjusted in length, it is obviously easier to shorten them than to lengthen them.  Secondly an antenna that is exactly a half-wave long has a theoretically infinite impedance so it would be very difficult to match that impedance.  If the wire is longer than a half-wave at the lowest frequency in an amateur band, it will not misbehave within that band.

The Halfer is actually just a familiar half-wave antenna oriented ”on end” rather than being center fed as is the common dipole familiar to radio amateurs.  The makes it much easier to put up.  The EFHWA article illustrates several different configurations.  For casual short range contacts, the inverted L is the easiest way to put up the Halfer.  If the horizontal section is at  least 20 feet above ground, most of the radiation will be at a fairly high angle which will bounce off the ionosphere close to your location.  If the antenna is erected vertically, most of the radiation will take place at a very low angle, and will favor DX type operation in good conditions. As with the usual center fed dipole, the Halfer can be put up in an inverted Vee shape.  This may be the easiest installation since it needs only a single high support.

A couple of compromise configurations are also useful.  If the inverted L is arranged with half the wire vertical and half horizontal, it puts the radiation portion at the highest point.  Since energy is radiated from the middle, it combines both vertical low-angle and horizontal high-angle components.  If the Halfer is set up as a “sloper” less than 45 degrees from the vertical, it combines low angle radiation with some directivity toward the low end of the antenna.  The sloper is also often the easiest way to put up a single wire antenna like the Halfer.

The figure on the back of this sheet shows some detail on the inverted L.  The three insulators are used as follows.  One is used at the far end to attach to the support line.  The end of the wire is already passed through a hole in the insulator and knotted.  The support line can be simply run through the insulator and tied in a common “granny” knot.  The antenna wire is run thorough the second insulator and not tied.  The second support line also is passed through, but tied to the insulator.  This allows the antenna wire to "free float" for ease of erection.  The third insulator is tied to the lowest part of the antenna and another support line is passed through the insulator and tied off to a support.  The free end of the wire goes to the antenna tuner.

Mounting and orientation of the counterpoise quarter-wave wire connected to the ground side of the tuner is non-critical.  Most of the time it can simply be laid out on the ground out of the way, but not coiled up.  Its primary purpose is to decouple the feedline to the antenna tuner by providing a low impedance to ground.  If a large metal object or very short ground connection is available, the counterpoise may not be needed.  

AVAILABILITY
Sorry, the Halfer Kit has been retired and is no longer able to be provided.  Use the diagrams on these web pages to homebrew your own.

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