|The CE0Y-7-m-Triple-Leg||The Battle-Creek-Special||The C-Pole|
The C-Pole-Antenna, Examples for 14 and 50 MHz (by DK7ZB)
|The C-Pole had been described first by Brian C. Cake (KF2YN) in QST
2004, No. 4, P. 37-39 "A Ground Independent Vertical
It is a folded half-wave dipole with an asymmetrical tapped 50-Ohm-point in the lower part of the antenna. I have modified the C-Pole for a greater bandwidth. Therefore the parts 1 and 2 are longer than in the original description and the gap between parts 2 and 3 is greater. The dimensions are < lambda/4 in the height and it is easy to build.
It is a special type of an "OCF"-Antenna (Off-Center-Feed). These antennas show a tendency for common waves. For this reason it is obligatory recommended to use a current balun for the feeding.
I have built the C-Poles with insulated 1,5 mm2-Copper-wire. For the sections 1 and 4 I have used insulated PVC-tubes as spreaders and support for the wires.
The gain of the antenna is -0,75 dBd in free space. With the balun the antenna handles 1 KW HF SSB/CW.
With the dimensions in column 2 it is possible to build C-poles for other bands
The patterns above ground:
Red = 3 m (Elevation 20°)
Blue = 4 m (Elevation 18°)
Left: The current balun, 2x4 turns Aircell-5 on FT240-43
Right: Mounting of the PVC-tube with two clamps and the balun box
Adjustment of the Antenna
the resonance of the antenna is set to 14,175 MHz, the SWR remains
<1.6 over a bandwidth of +/- 175 kHz. If the resonance point is just
below, it usually suffices to make a correction by shortening the section
3. In the opposite case, it must then be extended accordingly.
The C-Pole-Antenna for the 50-MHz-Band
The balun is wound with 2x5 turns RG178 on a FT140-43 core and handles 100 Watts. For more power
use the balun as described for the 20-m-C-Pole. Wire is 1,5 mm2 PE-insulated copper.
The Lengths for the Bands 6 m, 4 m and 10 m