woensdag 3 april 2024

Impedance of the inverted L versus number of radials

Before removing the radials of the inverted L (in fact 2x inverted L for 160m and 80m, but connected to a common balun and common radial system) to restart lawn mowing, I conducted some tests to observe the effect of the number of radials on the impedance properties of the antenna. First with 10 radials, each 21m long, then with only 4 radials, and finally with a single one. It should be noted that there is a 1:2.47 balun present in this system.

I did the test for both 80m and 160m.

End of the 160m season

 The winter of 2023-2024 is definitively over, and so is my 160m season. With 17 new worked and confirmed countries added, the counter reaches 95 confirmed DXCC entities on Topband. Only my QSO with JT1CO from 2022 remains unconfirmed.

With highlights including Yemen in FT8 and East Timor in CW, I can look back satisfied at a successful season.

Just 5 countries left on the way to the 10B-DXCC and only 4 zones needed for 160m WAZ.

High performance results with modest equipment on 30m


It's sometimes astonishing how much can be achieved with limited resources. Last night, I was active on 30m in FT8, using 250W and the Optibeam OB1-30 dipole antenna at a height of 15 meters. Clear, the Optibeam dipoles are very good performers.

Below are the locations where my signal was received over a period of about ten hours.

CQWPX contest : just for fun and lowband inverted L antenna testing


After my bad experience with using the inverted L antenna on the higher bands, contrary to the results I had with it in FT8, I made a second attempt during the WPX SSB contest on 10 meter with 100W. It was a struggle for every QSO, but ultimately, I managed to work almost all continents with an antenna that was not made for it at all. So, anything is better than doing nothing.

maandag 4 maart 2024

Beverage on ground (BOG) poor performance on soily ground

I already mentioned it in a post a few weeks back, but now I have also found confirmation of my findings: a Beverage On Ground (BOG) loses its performance when it lies on soily ground.

In an article (https://rudys.typepad.com/files/qexjul-aug-2016-bog.pdf) written by N6LF and published in QEX, this conclusion is also drawn : " Initially the BOG and the loop were clearly superior to the vertical, and throughout the 18 months the loop performance was very consistent. The BOG worked well at first. However, over time and especially during the two intervening winter wet seasons,I noticed the BOG signal amplitudes dropping off significantly (-15 dB) and the S/N improvement dropped to no better than the vertical."

This aligns exactly with my findings. When the BOG is installed at the end of October, when the ground is still dry, I notice an advantage in terms of reception. From the moment everything is wet, the vertical performs better.

zaterdag 2 maart 2024

DXCC 320 : H40WA Temotu Province

Never expected a QSO with this H40WA expedition because of the lack of higher band antennas.

Worked H40WA on 21Mhz FT8 with my 160/80m inverted L + MFJ shack-tuner and using 200W.

He received me at -21dB, I did at -18dB.  This is at the limit of FT8 and should never have been a contact in CW nor SSB.  So happy that he picked me out of the huge pile-up.

Result of the CQWW CW 2023 contest

Happy with it !  

4th place worldwide without a convenient receiving system.  My home-made inverted L is clearly a good antenna.