Here are some practical tips on using passive antennas. For the engineer these tips can be proven with theory but we now present them as ideas and you can experiment for yourself.

• A wire antenna can be too long for omni-directional receivingon higher frequencies. For example, a 60 meter dipole is sensitiveto signals perpendicular to the antenna plane. As the number ofwavelengths increase, the antenna patterns change and the antennabecomes directional off the end(s) of the wire. A second, shorterantenna may be a good investment for reception on the higher frequencies.

• Given a horizontal antenna and a vertical antenna mountedat the same height above ground, the vertical antenna will bemore responsive to low-angle signals for DX reception. The horizontalantenna's sensisitivity to low-angle signals is best when it isat least one quarter-wavelength above ground.

• Listening to stations on the lower frequencies -- more thanone skywave hop away -- during the twilight periods can be a challengewith rapidly fading signals over short periods of time. The fadingeffects are caused by the changing skywave reflection points asthe E, F1 and F2 layers "tilt" while going through transitionfrom light to dark or vice versa. Switching to and from a secondantenna with the opposite polarization can help to compensatefor the fading effects. We have found a lower antenna often receivessignals better, but by late at night when the twilight effectshave disappeared the higher antenna -- responsive to the low-anglesignal -- is the antenna of choice.

• A loop antenna mounted horizontally a quarter-wavelength abovethe ground is sensitive to high skywave angle signals and affordremarkably stable reception of signals one skywave hop away. Becauseof its lack of sensitivity to distant low-angle signals, the antennacan actually reduce co-channel interference.
• A sloped antenna offers a bit of directivity in the directionof the slope. Multiple antennas for different directions can beattached to one antenna support and switched with a remote antennaswitch.

• Multiple antennas can interact with each other to diminishany desired directional effects by acting as a passive radiator.Use antenna switches that ground the antennas not in use.

  Active Antennas