A bridge on the Vistula river as an element of an antenna – earth dipole tests continued

Encouraged with the outcome of latest earth dipole tests I decided to continue testing of those interesting antennas.

This time, however, I aimed at:

  1. testing the possibility to transmit in 136 kHz
  2. checking how a good quality electrode will impact the antenna
  3. confirming that an earth dipole can work effectively above the ground with low resistance
  4. testing an antenna of this length to be able to receive signals at the lower end HF

I used a 0.6 mm copper plated steel pole (due to cost and no alternatives available). Resistance for the pole was over 1kOhm. The cord was spread across the field lying on the grass or in the bushes at the height of 0 – 2 meters above the ground level.

The antenna was placed max 15 meters above water at the banks. I used a nearby bridge as an electrode. The bridge’s dimensions:

  • 982,5 m long
  • 18,6 m wide (the deck was 12 meters)

This bridge was restored in 1950, that’s why I doubt that after 68 years all elements are well grounded. A 10mm wide and over a dozen meters long aluminium strip was dipped in water and served as the other electrode. The entire antenna including the bridge was ca. 3 km.

Specifications:

  • 50-250kHz antenna impedance was 800Ω
  • the resistance of the bridge at 70Hz was below 1Ω
  • the resistance of the antenna for DC was over 1kΩ
  • the resistance between the antenna and the ground for DC was ca. 80kΩ
  • the resistance of entire antenna for DC was ca. 2Ω

This is how it worked at LF and MF

https://youtu.be/-LhH-mn-F-Y

The SWR of the antenna with a transformer switched at 1:1

The SWR of the antenna with a transformer switched at 1:4

The SWR of the antenna with a transformer switched at 1:9

The SWR of the antenna with a transformer switched at 1:16

Conclusions:

  1. The antenna works in 136kHz. Below you’ll find a signal received in Gdańsk (40 km away). I didn’t try WSPR or PSK as I was only equipped with a battery.
  2. The bridge serving as an electrode influenced the antenna’s efficiency, lowers the impedance and broadens the bandwidth. Poniżej SWR anteny z transformatorem  o przekładni 1:16 bez zastosowania mostu jako anteny.
  3. An antenna spread above ground with low resistance can be used for ham radio.
  4. This antenna serves well also at KF lower bands. Below you’ll find the antenna working in 3,7MHz and 7MHz. There were no tests at 1,8MHz as all the tests were carried out in the daytime.

https://youtu.be/1WuevphxlvM

https://youtu.be/o27-oE2KEPg

More tests soon.

 

Have a look at my previous tests:

https://klubnl.pl/wpr/index.php/2017/11/26/kolejne-proby-z-antena-dipol-ziemny/

https://klubnl.pl/wpr/index.php/2017/08/01/proby-z-antena-dipol-ziemny-o-dlugosci-okolo-600m/

https://klubnl.pl/wpr/index.php/2017/06/22/proby-z-antena-dipol-ziemny/

Testing earth electrode once again

Last time I tested earth electrode I felt encouraged to work on this some more. Beneficial propagation during this time of the year and the fact that I’ve been well drilling on my land were more than a good excuse for experimenting with an electrode dug 13 meters below ground level. The electrode was placed right in the well and dipped in water of 50 cm. The other electrode was a 1,5 meters long piece of steel beam with ‘C’ crossed plunged in the nearby lake. The distance between the two electrodes was ca. 100 meters.

Inox mesh serving as an electrode wound on a 160mm pipe.

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Experyment with antenna earth elektrode about 600m long

Successful experiment with earth dipole about 150m long encouraged me to experiment with a longer antenna about 600m long. I used industrial earthing on one side and steel beam with ‘C’ cross section immersed in the water on the shore of a small lake served as the other electrode. I used industrial earthing on one side. The antenna consisted of two wires about 150m (symmetric cable) and 600m (PKL) long,

The resistance of the antenna for DC was about 1kΩ.

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Earth Electrode Antenna Tests

I conducted my first tests with earth electrode antenna in the nineties with the use of hot water installation. While drilling a well on my piece of land in the countryside I thought this could be just the right moment to explore this idea a bit more. A test drill for 5 meters provided a hole where I put an electrode. However, the soil in the hole was utterly dry and the electrode was not covered with it – it was just a two meters long aluminium L-beam. High resistance of this connection apparently influenced the antenna’s efficiency. A steel beam with ‘L’ cross section immersed in the water on the shore of a small lake served as the other electrode. The distance between the two electrodes was ca. 150 meters.

 

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