Ground Plane for 80 meters without tuner.

Being a HAM for years I always thought of an efficient antenna. My current goal is to make the effective antenna for 80 meters so that I could spend long winter evenings on listening to DXes. I'm living in a private house in the heart of the big city and not able to hang out wire antennas at enough height. Although my experiments with ground standing masts and wire antennas have shown me some positive result I decided to build the one-band GP.



The goal is: to have an efficient and not hard-to-build antenna. This antenna should have a minimal number of tunable pieces to prevent damage to the transmitter or PA.

I had started sniffing around and found nothing but some multiband antennas described by Igor Goncharenko (DL2KQ). They are almost perfect but do not fit my needs - the presence of the tuner makes them inappropriate to me. Then I have started building my model and below is a result of this work: monoband ground plane with four shortened (and therefore non-resonant) counterpoises and capacitive load on the top.

The antenna is 16.5 meters high, has four 5 meters long counterpoises and two 10 meters long wires mounted onto the top of the vertical part. The antenna has the impedance 50+4j Ohms on 3.55 MHz. The BW by the SWR 2:1 is 144 kHz.

Below are some screenshots are taken out of the MMana. As you can see the ground settings affect the final value of the impedance.

I played with the model and realized that:

• the number of counterpoises affects their length - the more counterpoises you have, the shorter they can be.
• shortening the counterpoise decreases the reactance of the antenna, but too short counterpoises make the reactance negative and big.
• the length of wires of the capacitive load affects both active and reactive resistance - longer wires increase the mentioned values, but reactive resistance grows faster than active.
• the angle between wires of the capacitive load and the vertical part affects both active and reactive resistance - raised wires increase the mentioned values, but active resistance grows faster than reactive.