Back east I had a small tri-band yagi on a 50ft tower and large wire arrays hung from 80 foot trees. I hardly ever used my amp. When I moved out here I got caught up in the "one antenna for multiple bands" craze. Performance was so-so with these multi-band wire antennas - I seem to need to have my amp on almost all the time. Is this maybe just what HF propagation is like in the center of the country (vs the east coast)? So I figured I should start the thinking about a tower and tribander. To that end, every yagi starts life as a dipole - so let's try a high single-band horizontal dipole oriented for east-west propagation. So up goes a 10M dipole and later a 15m dipole, both at 35 feet. Fed with coax - no balun (center fed dipoles out in the clear rarely need baluns - contrary to the balun-crazy folks). All I can say is wow. What a difference. I have a 4 antenna switch so I can switch between 4 different antennas on both 10 and 15 meters. The dipoles are lights-out better 90% of the time. Some times 2 s-units better. Get a 15 or 10 meter half-wave dipole up more than a 1/2 wavelength high, running north/south (for east/west propagation) and be happy. I'd rather have a good signal on one or two bands than have a crappy signal on many bands.
EZnec antenna modeling software is now free. FREE. Modeling all the antennas I have, it is easy to see why a simple single-band dipole with two major gain lobes works better than using a low band antenna on the higher bands - the low band antenna on the higher bands will have multiple nulls in many directions. I knew this all along but underestimated how much this characteristic would impact signals in practice.
Get a single-band dipole up!
Comments?
Dave, kx3dx, Larkspur
