Constructing a cylinder dipole
The cylinder dipole consist of two open aluminium cylinders and a coil. The coil is connected between the cylinders and is hanging below the cylinders. I constructed my first cylinder dipoles from aluminium energy drink cans that I found on the street. To get open cylinders, I remove the top and the bottom of the cans.
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| Cylinder dipole - PA1B |
Energy drink cans
The cylinder dipole, that is tuned to 15 m, but also works very good on 10 m, consists of two aluminium energy drink cans of 500 ml. The top and the bottom of the cans were removed.
The two cylinders form the radiators of the cylinder dipole. The current on the surface of the cylinders, causes the radiation.
The coil has 9 turns and is wound on a PVC tube with a diameter of 80 mm. The taps are one turn apart.
I have a lot of fun with this cylinder dipole in the shack at the first floor, 4 meter above the ground. This cylinder dipole can also be used on 20 m, with lower efficiency.
Parallel resonance
The cylinders show a large self capacity. This capacity is much larger than the capacity of a wire of the same length as the cans. The capacity of the cylinders and the induction of the coil form a parallel LC resonant circuit. The impedance of this LC circuit is high at resonance.
Please notice, that this parallel resonance, is what makes the difference between the cylinder dipole and a dipole with very short wires.
Tuning
The cylinder dipole is tuned by choosing the number of turns of the coil.
Feed point
I made taps, at the center of the coil. The connection on the taps of the coil, form a feed point with low impedance, to which the 300 ohm twin lead is connected. The lower the number of turns between the taps, the lower the impedance will be. I had good results with the taps just ONE turn apart.
Please notice, that because the taps are placed at center the coil, the ribbon will not radiate it self.
Matching
The cylinder dipole is matched (not tuned) by the symmetrical tuner in the shack. The tuner is adjusted to the lowest SWR.
Multi band antenna
The cylinder dipole can be used as a multi band antenna, simply by matching the antenna to a SWR of 1:1 on the band that you want to use. That's all.
Build - Work - Analyse
I am curious about your results.
The cylinder dipole, that is tuned to 15 m, but also works very good on 10 m, consists of two aluminium energy drink cans of 500 ml. The top and the bottom of the cans were removed.
The two cylinders form the radiators of the cylinder dipole. The current on the surface of the cylinders, causes the radiation.
The coil has 9 turns and is wound on a PVC tube with a diameter of 80 mm. The taps are one turn apart.
I have a lot of fun with this cylinder dipole in the shack at the first floor, 4 meter above the ground. This cylinder dipole can also be used on 20 m, with lower efficiency.
Parallel resonance
The cylinders show a large self capacity. This capacity is much larger than the capacity of a wire of the same length as the cans. The capacity of the cylinders and the induction of the coil form a parallel LC resonant circuit. The impedance of this LC circuit is high at resonance.
Please notice, that this parallel resonance, is what makes the difference between the cylinder dipole and a dipole with very short wires.
Tuning
The cylinder dipole is tuned by choosing the number of turns of the coil.
Feed point
I made taps, at the center of the coil. The connection on the taps of the coil, form a feed point with low impedance, to which the 300 ohm twin lead is connected. The lower the number of turns between the taps, the lower the impedance will be. I had good results with the taps just ONE turn apart.
Please notice, that because the taps are placed at center the coil, the ribbon will not radiate it self.
Matching
The cylinder dipole is matched (not tuned) by the symmetrical tuner in the shack. The tuner is adjusted to the lowest SWR.
Multi band antenna
The cylinder dipole can be used as a multi band antenna, simply by matching the antenna to a SWR of 1:1 on the band that you want to use. That's all.
Build - Work - Analyse
I am curious about your results.
Hallo Bert, nu je zo bekend bent geworden (CQ magazine) ben ik dit artikel nog maar eens gaan lezen. Hoe kom je aan de gegevens van die spoel van 9 windingen?
BeantwoordenVerwijderenGeld dit ook nog voor een 40m blikjes dipool? Is dit ook te maken voor 160m? Uiteraard met grotere blikken. Hoe groot zouden ze moeten zijn om enigzins effektief te stralen? Moet ik denken aan 2 60ltr vaten? Of meer aan 2 200ltr vaten ;-). En hoe groot zou de spoel dan moeten worden? Je merkt, ik heb wel wat grootheidswaanzin....73, Bas
Hallo Bas, Ik ben altijd uitgegaan van de blikjes. Red Bull en Monster. Spoel Daarna heb ik de spoel gemaakt. Door te proberen kom ik op het aantal windingen. Meer windingen verlaagt de resonantiefrequentie. Als het teveel windingen worden, dan kies ik een spoelvorm met een grotere diameter.
VerwijderenDe Monster energie drank blikken geven QSO's op 15 m, maar dan moeten de siganalen wel S+ zijn. 73, Bert
Hallo Bas, voor de afmeting van de cilinders, verwacht ik dat de lengte en de diameter evenredig met de golflengte vergroot moeten worden.
VerwijderenEchter... Ik heb met de Monster blikken op 15 m wel QSO's gemaakt, maar ik weet niet of deze antenne een goed rendement heeft of dat het de conditities zijn, die het verschil maken.
Monster: 16 x 6,5 cm --> voor 40 m worden de cilinders: 50 x 20 cm. 73, Bert