donderdag 24 december 2015

Cylinder dipoles on 10 meter

The cylinder dipole can be used as an indoor HF antenna, with VHF/UHF dimensions. Our test showed that the cylinder dipole constructed from aluminium energy drink cans can be used as a multi-band antenna on 10 m to 15 m.

In the weekend of the ARRL 10 meter contest, Alex SA5BFZ and I (PA1B) made CW QSO's on 10 meter both with our indoor cylinder dipoles.

Cylinder dipole of Alex SA5BFZ
Alex operated on Sunday, outside of the contest. He made 2 excellent QSO's from Sweden with Spain on 10 meter and a QSO with Russia on 17 m. Alex used the cylinder dipole that consists of two  500 ml energy drink cans and a coil of 80 mm with 8 or 9 turns. The photo shows the cylinder dipole of Alex.

I participated on Saturday and Sunday for two very short periods in the ARRL 10 meter contest. I was curious what my  Red Bull  antenna  would do on 10 meters. I never had the opportunity, to use it before on 10 m, due to the lack of propagation on 10 meters.
Coil and cans.     PA1B
The Cylinder Dipole principle
is not yet in the text book
I worked 2 stations on both days, within 8 minutes and within 5 minutes. With only 10 meter to operate, I was fully depending on the propagation on this band. My cylinder dipole with Red Bull cans is doing fine.
The signals must be S8 or stronger, then it is easy to make a QSO. In 3 QSO's I used 2.7 W. In the QSO with RU6AV I used just 0.8 W.
I used a cylinder dipole with two  Red Bull cans  and a coil of 40 mm with 14 turns.

Both cylinder dipoles of Alex and me are doing fine on 10 meters. We made QSO's over large distances within Europe, with low power. The table below shows both call signs of our QRP stations and the stations that we worked, the distance in Miles and the used power in watt.

Lowest possible power
We both operated with the lowest possible power.  We reduce our power according the reading of the S-meter before we answer a CQ. To use the lowest possible power we must use S&P.

How to compare
Because we both used the lowest possible power, it is possible to compare the QSO's.
The QSO's can be compared by calculating the value of the Miles/quare root of the power or by calculating the Electrical field strength at the receive antenna.

In the last column I compare the QSO's in dB. The higher the value in dB, the stronger the signal.
I choose my QSO with RN3GQ to be 0 dB. The other QSO's on 10 m are made under better conditions.
The value in dB shows the influences of the propagation and the antenna of the other station.
The higher the value in dB, the stronger the signal.
I say Thanks to for the link from their interesting site to this Blog entry.


Miles per WHAT?
The calculation of Miles per Watt can not be used to compare QSO's. To double the distance we need more power. The power must be increased 4x to get the same signal strength.
The value  Miles/SQRT(watt) is calculated from the distance in miles divide by the square root of the power in watt. This value is very easy to calculate and is an excellent propagation indicator.
The higher this value, the better the propagation. (The value is NOT accurate over a short distance.)

Electrical field strength in V/m
E = electrical field strength  in  V/m
P = used power in watt.    
R = distance between the radio stations in meter.

An other way to compare is to calculate the Electrical field strength E.
The lower the Field strength the less power is needed to cover the distance, the better is the propagation.

2 opmerkingen:

  1. Good!!! Have you the dimensions for the cylinder dipole for 40 m.?
    Thank you for your experimenting low power communications: iz3ayq

    1. Hello Fabio, thank you for your question.
      In order to use the cylinder dipole on a lower the frequency, both the diameter and the length of the cylinders, must be increased in the same ratio. 21 MHz --> 7 MHz is a ratio of 3
      I would use two cylinders, with a diameter of 20 cm and a length of 50 cm.
      Thank you for your nice words on the use of low power. FB. 73, Bert