zondag 31 mei 2015

Cylinder dipole at 21 MHz

Cylinder dipole
Click on the pictures to enlarge
After the experiment with the Red Bull antenna, I built a second Cylinder Dipole with two energy drink cans of 500 ml. The cans together with the coil resonate at 16 MHz.
The 300 ohm ribbon is connected to the point at the top of the coil (in the picture) with the red and yellow alligator clips (See the white arrow in the top of the picture). The antenna is hanging from the ribbon. I can tune the cylinder dipole for the a SWR of 1;1 with my symmetrical tuner.

Cylinder dipole
PA1B Cylinder Dipole.  The current at the surface of the cylinder generates the field.

Closed cylinders  
In this antenna I used the complete can, without removing the top and the bottom of the can, to keep the construction simple.
Closed cylinders are much stronger than open cylinders.

500 ml cans
Although it is not easy to compare two antenna's, that were used in two different contests a week apart, the cylinder dipole with the 500 ml cans is probably better than the Red Bull antenna.
In general the cylinder dipoles are very quite on receive.

On the air
In the H.M. King of Spain contest I made QSO's on 7 MHz, 14 MHz and 21 MHz.
Most QSO's were made on 21 MHz with a power of 3.6 W to 360 mW all over Europe.
This cylinder dipole with two 500 ml cans works better on 21 MHz than on 14 MHz.
The antenna is "detuned" to 21 MHz with the symmetrical tuner.
On 7 MHz it was very difficult to make a QSO. The QSO's on 7 MHz were made over a short distance. NVIS. I estimate that the lower efficiency at 7 MHz reduces the signals with 10 dB.
The table below shows the DXCC countries per band and per power category.

Across the Atlantic
I very much enjoyed the QSO with N1KWF in New Hampshire over a distance of 3490 Miles, with a power of 3.6 Watts.

Please notice that that the cylinder dipole with 500 ml cans:
 * has a length of 15" (38 cm)
 * is placed in the shack,
 * at a height of 4 meter above the ground.

Click on the table below, to read the hand written log, in which I write down the power in each QSO.
List of QSO's with the cylinder dipole, with cans of 500 ml PA1B
The QSO's in red are more than 1000 Miles per Watt QSO's.
DXCC's per band and per power category PA1B

2 opmerkingen:

  1. Hallo Bert, het hele verhaal gelezen en sta er versteld van. Het is nog net geen dummyload en toch straalt het zo goed dat er transatlantische verbindingen met QRP mogelijk zijn. Zo zie je maar, men klaagt wel eens dat ze geen antenne kwijt kunnen en beperkt zijn m.b.t. zenden. Maar jij bewijst dat het zo ook prima gaat. Het is natuurlijk wel een kwestie van contesten (met sterke stations) uitzoeken en niet willekeurig op een avondje gaan roepen. Maar die vrijheid heeft toch iedereen. 73, Bas

    1. Hallo Bas, De goede werking wordt bepaald door de hoge capaciteit tussen de twee blikjes en het optransformeren van de spanning m.b.v. van de spoel die als autotrafo werkt. Oordeel zelf, op de dummy kom je het dorp niet eens uit. 73, Bert