ILERTENNA

| abril 6, 2014

ILERTENNA

End-Fed QRP Tuner Kit

The most popular antenna is the center-fed dipole which has a nominal impedance about 75 ohms which can be easily adapted to a 50 ohm feed. When we want to feed a similar lenght antenna, such as the half wave through one of its ends, its impedance is close to 3000 – 5000 ohm and needs a transformation system to match to a 50 ohm transceiver.

In the 20s of the last century «zeppelin» airships encountered a problem when installing their huge communication antennas. Unlike the great ocean liners in which the antenna was hung between the masts, in the «zeppelin» it was impossible to use this system. The solution was to left it hanging feeding it through its end. The antenna was connected to a system to automatically deploy and rewind it for take off and landing, respectively.Such antennas were renamed as «zeppelin antennas». The «end-fed» antenna, as the name suggests, are similar to the «zeppelin» ones although the type of coupling is somewhat different.

The use of a half-wave antenna fed by one end has certain advantages compared to a conventional dipole. The impedance of the antenna is around 3000 – 5000 ohms and very little RF energy flows to ground. The coaxial cable from the tuner to the rig will act as a counter-antenna. If used as a vertical antenna, it is not necessary to use ground radials for improving the efficiency. The point of maximum radiation is at half the length of the antenna. For example, for a 40 meter antenna, if it is hanging vertically from a tree or polethe point of maximum radiation is 10 meters above ground level, without having to have radials on the ground.

Obviously, installing an end-ed antenna is really very easy. In practice, especially for QRP enthusiasts who like to do field trips, the antenna has important advantages: it only needs a fixing point, usually a tree or a fishing rod, and requires little or no coaxial cable, thus saving weight in the backpack.

The perfect tuner for SOTA, backpacker and traveler
40 m – 15 m end-fed QRP Tuner

ILERTENNA End-Fed QRP Tuner Kit ILERTENNA 40 m - 15 m end-fed QRP Tuner

ILERTENNA GENERAL SPECIFICATIONS

  •     Frequency Coverage: 40 – 15 m (30-10 m modified).
  •     Antenna type: «end-fed» or «zeppelin»
  •     5 watts CW 10 watts P.E.P.
  •     LED SWR indicator.
  •     Only weighs about 100 gr.
  •     Connectors and controls: Tune. Tuning/Operate switch. Antenna sockets. BNC to Radio.
  •     Size: 80 x 50 x 22 mm.
  •     All components. Box, PCB, knob and connectors included.

ASSEMBLY

The assembly of the ILERTENNA is very easy. Please notice that the PCB does not have any hole for part insertion. All parts are soldered over the pads as if they were for Surface Mounting.


ILERTENNA PCB

Resistors R1, R2, and R3 are composed by resistor couples which will be soldered as per the pictures (see «Placement of R1, R2, and R3»). Toroidal transformers T1 and T2, as well as the polyvaricon need special attention as addressed on this manual.

IMPORTANT

The front panel of the ILERTENNA serves also as the PCB for placing the parts.

Take care not to scratch it during assembly. It may be a good idea to place it while assembly over cloth or other protecting material.

ILERTENNA End-Fed QRP Tuner Kit

ILERTENNA SCHEMATIC

ILERTENNA SCHEMATIC

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