Fellow Amateurs…

Let’s Look At Antenna Technology Realistically

For the last 50 years there have been no advances in vertical “technology” — a technology consisting of vertical wire, fed at the base, surrounded by any number of radial wires. To operate multiband, traps had to be placed at appropriate points to shorten the antenna to a 1/4 wave on various. Manufacturers extolled their antennas based on “low loss” trap design, implying their antenna would outperform the others. Yet big signals on the band did not come from these verticals. DX contacts, with the vertical’s well known low angle radiation, did not happen consistently. The vertical became a 2nd class citizen used by those with little space, minimal finances or a need to comply with local restrictions.

If a new amateur asked what antenna to put up, the common response from another ham was, “put up a dipole”. Why? Because a conventional vertical is the most inefficient, noisy antenna available for amateur use and the trap version is even worse.

Where Does The Power Go?

For example, the 26 foot vertical on 80 meters should be 66 feet high. The “missing” 40 feet is replaced by coils (trap). This short antenna has a radiation resistance of 4 ohms. It’s a “virtual” resistor, which when power is applied, radiates RF That, however, isn’t the only resistor in the antenna system. There are more. The significant resistor is called earth loss, which is a function of the radials and ground. If three radials are used, the earth loss created is more than 30 ohms. We now have an antenna with 4 ohms that radiate and 30 ohms that warm the ground for a total of 34. But only 4 ohms radiate! if 100 watts powers this antenna, only 12 watts actually radiates. If you add lossey traps equaling 2 ohms, the power out drops from 12 watts out to 11 watts out. While traps have their own deficiencies, it is the huge earth loss that really matters. Fortunately, GAP technology conquers this problem.