Sky Ham Radio End Fed Antenna , Resonant 40 – 20 – 10

Today many Hams encounter big problems when they want to install a good antenna. Many live in an apartment building, or in an area where the rules do not allow you to install a fixed antenna that gives good performance. So many, by necessity, must be satisfied to operate in portable. They therefore need an antenna that is easily transportable, can be installed in a few minutes, and give acceptable performance, well comparable with those of many fixed antennas. Moreover, to operate in Portable allows you to combine our passion with the possibility to take your family to a nice trip, maybe in a nice place, where the children can run in the open air while we Hams can finally find satisfaction in our beloved hobby. Finally, if you could find an antenna that you can use, maybe occasionally, even at home that would be the best: an antenna that you can quickly run from a window to a nearby tree, or another building, or simply to a telescopic pole (there are many made of fiberglass, lightweight and quick to assemble)… …. And then it desappears in a few minutes. This antenna exist: it is the classic “half-wave dipole” powered, however, at one end rather than at the center. The problem that arises is in the adaptation of impedance; at the end of the dipole the voltage is maximum, the current is minimum and the impedance becomes some thousand ohms: not easy to adapt to the 50 ohm required by our Rig, and even if we count on the ATU of our Rig we will have to deal with a very high SWR, strong losses in the cable and probable interference TVI. We have thoroughly studied this issue; we have done hundreds of tests, built dozens of Balun and Unun, and in the end we created our End Fed Multiband Antenna.

 

Here are some of its features, which make it unique: 

• First, it is well known that any “unbalanced” antenna simply must have a “return path” for the Radio Frequency. The vertical antennas require radial, possibly many; and also a half-wave dipole needs it. It could, as many do, provide for the installation of a system of “counterweight” consisting of one or more wires to be spread on the ground; good solution but very uncomfortable, and it is not always possible to place them. Others suppliers, without doing much to make you know, are counting on the feeding coaxial cable whose screen becomes the “counterweight”. The problem here becomes that your coax cable can have any length (and this affects resonance), and in any case at the end that you will connect to your Rig there will always be some radio frequency, which disturb your Rig; and in certain cases you will experience it, in the form of “pinching” the lips or the hands. Our antenna is different: the special project of its Transformer Adaptation involves a precise length of coaxial cable (don’t worry, its an abundant 30 feet), which is comprised and permanently fastened; also at its end is installed a “Choke” filter that locks the RF before getting into your system.

• All components are of the highest quality; starting with the wire antenna, which is the famous “Silk Wire 532” of Wireman. Not curling, slips silky smooth, and very resistant and UV resistant for years. The fixing clamp of the Antenna wire is not a simple nut, but a professional Hirshmann; so it will be easy and quick to change the wire with another, for the change of bandwidth.

• The antenna is available in several models, including two Multiband: one for 40 – 20 – 10m, and the other for 80 – 40 – 20 -10 meters. Used in these bands, the SWR ratio is very low, and this limits the standing waves, increases the performance and save the power loss introduced by your ATU.

• The antenna is “cut” for the CW band but you can “cut” it easily for SSB: at both sides, the Antenna wire is fixed in an “interlocking” way, and is very easy to trim even in the field, and adjust the length to optimize it to your habits.

• The small “trap” that separate the two sections is made to slide without getting caught, if you have to pass it through the branches of a tree, End Fed Antenna

• The antenna has been tested in “real” conditions most likely used, not on a 60 feet tall tower at the seaside… We specially built a “field test” place, that goes from the window of my lab to a nearby tree. Still, even a few meters from the ground and with houses around we got excellent reports from the network of “Reverse Beacons”; you will find a summary of one of these tests in a file attachments 

• Although many will use it in QRP or maybe  10Watt, we have tested our Antenna at lenght with 200W in CW, and up to 350W peak power without problems. We still recommend it, without fear, for a continuous power of 100W in CW or SSB. If you need to use it outdoors, you just have to find the tallest tree in the area, throw a string through the branches and knot it to the end of the antenna wire. On the other side you can safely fix the Transformer Unit to your car, or to another tree, anything. Spread the coaxial cable all over to the ground, possibly in the opposite direction or perpendicular to the wire antenna and you’ll be ready to operate. If you want to use it at home, take care to leave as much as possible of the coax cable dangling out the window.
  
• The Antenna length is 12 meters (39 feet) and the weight is 600 grams (21 ounces)
  A handy, soft carrying bag with shoulder strap is included. – See More : Link

 

 

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