END FED WIRE ANTENNA

 

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The end fed wire has to be one of the best cost effective and simplest multi band antennas. They are easy to erect and can cost almost nothing if you have enough wire handy. Almost any type of wire can be used, any medium gauge multi stranded pvc coated wire or single strand enameled copper wire. (I use 16 gauge pre- stretched enameled copper wire). This antenna will suit most houses and gardens as it can be horizontal, part horizontal, vertical or sloping to fit your available space.

Any length of wire can be used, but the length will determine which bands you can use. For shortwave listeners the lengths are not critical but for transmitting the chart below will give a good starting point.

WIRE LENGTH

BANDS

10.5m
40,30,17,15, and 12m

15.5m
80,40,20 and 12m

26.5m
All bands (tuning may be difficult on 10m)

The wire lengths above may need some alterations due to the geometry of your QTH, height and nearby buildings.

There are some drawbacks with this type of antenna, it is unbalanced and in some cases may rise to TVI problems in built up areas. It also requires the use of an ATU (antenna tuning unit) and you will also need a good earth connection. As you can see from the diagram the ground wire is connected to the the earth terminal of the ATU,  the other end is connected to a copper earth rod driven into the ground.  The longer the rod the better but the ground wire should be kept as short as possible. Use a thick heavy gauge wire such as the type used for car battery leads or the braid from a heavy gauge coaxial cable.

If your shack is on the first floor or higher it may be difficult to get a good RF earth.  If the ground lead length is more than a small fraction of a wavelength you may need to use an artificial ground. This is a quarter wavelength of wire for each band in use, they must all connect to the earth terminal of the ATU.  The wires can be run outside, concealed around the skirting board or under the carpet of your shack, make sure the end of these wires are well insulated or use pvc coated wire as the free end of a counterpoise wire will carry very high RF voltages when transmitting.  The counterpoise wires will also reduce or remove any RF feedback or transceiver instability.  



Another idea is to use a length of wire one half wavelength at the lowest operating frequency. This requires a less extensive earth system (An earth rod driven into the ground without any counterpoise wires.)





ALTERNATIVE CONFIGURATION TO FIT  AVAILABLE SPACE. 

WARNING=MAKE SURE THE END OF THE WIRE IS WELL INSULATED TO AVOID RF BURNS.

COUNTERPOISE WIRES MAY BE LAID ABOVE,  BELOW OR EVEN ON THE GROUND.

I would recommend the end fed wire as a good antenna to start the hobby as it requires very little expense. I have worked stations all over the world on 20 meters,  all over Europe on 80 and into central Russia on 40 meters. Although I have not called for any real Dx on 40 meters, I have heard stations as far as central Japan.

http://users.whsmithnet.co.uk/m0dad/Homebrew/end_fed_wire.htm

Build a 2 Meter, 5/4 Wave Antenna

Many RASON members truly enjoyed last month's collinear antenna. This month I decided to build a 2 meter 5/4 wave antenna. This antenna is unique in that it is enclosed entirely in 3/4" PVC which makes the design a little more complicated. The primary problem is that PVC tubing has a significant velocity factor which causes RF to slow down. This means that an antenna encased in PVC will normally need to have it's physical length reduced by about 19%. To further complicate the design, a 5/4 wave antenna's impedance has a highly inductive component which must be tuned out to get a good match. Fortunately, the design in Figure 1 solves all of these problems.

http://www.rason.org/Projects/ant54/ant54.htm

Oz Report's Antenna

2m (144-148 mHz) Antenna with molded BNC connectors (the only kind worth anything in hang gliding harnesses).  

Five foot long total RG58C/U coaxial cable. 19.5" of unshielded center cable (for 144-148 meters) which you attach to your harness mains (using tape).

The ground wire is the exposed shielding wire, the mesh wire that normally surrounds the interior wire. This is how you hook it up in your harness: http://sahga.com/harness_antenna_2.gif.  

You can just tape down the braid also.

I have also had adequate success just cutting off the braid exposed ground line like this:

Click on above to view a higher resolution image. 

Connect the antenna, as shown in the diagram above, to your mains. I suggest in a manner to protect the junction at the end of the shielding from flexing, so run the shielding up the mains for a couple of inches, if you have the room. 

I have normally cut off the ground as it is sometimes a bit of a hassle to place horizontally along the back plate, but by leaving it on you have better matching of your antenna to your radio to get the highest signal power output. I've had good luck even with the ground gone.

The antenna is cut to 19.5 inches which corresponds to 144 mhz. You can cut the antenna a bit shorter for high frequencies if you like, although the differences are quite small. To know how long to cut the antenna (the single center strand), it is length (in inches) = 2808/freq in mHz. For example, for 147 mHz, length equals = 2808/147 = 19.1 inches.

http://ozreport.com/antenna.php

Single 5/8 Flower Pot Antenna

The Single 5/8 version of the Flower Pot simply substitutes a 5/8 wave-length section for the top quarter wave of the basic half wave antenna design. The arrangement is shown in the sketch below. The 5/8λ radiator uses a 0.2λ (shorted) co-ax phasing stub to resonate the 5/8λ element. In a conventional 5/8λ mobile whip, an inductor is used to bring the 5/8λ element to resonance; however, in this Flower Pot style of antenna, using a co-ax phasing (or delay) stub suits the construction technique and has the advantage of being able to be precisely determined and cut at the construction stage.

The antenna configuration is similar to, but slightly shorter than, the “Gain Sleeve” antenna described in the RSGB Hand-book (6th Edition – figure 13.99, which itself is derived from the reactance – or shunt – fed 5/8λ monopole antenna at figure 13.84 of the handbook).

The Gain Sleeve antenna achieves an effective radiating element length of one wavelength and, since the aperture is twice that of a half wave dipole, a theoretical gain of 3dBd (gain over a dipole) could be achieved.

However, note that the Handbook indicates that in practice, the Gain Sleeve antenna would realise about 2.5dBd. The effective radiating element length of the Single 5/8 Flower Pot is 7/8λ suggesting it would have somewhat less than 2.5dBd gain.

2m Construction