Hello, DXers Welcome to Antenna section – This Section is for Antennas : Specially Short wave / Medium Wave Radio Antennas. DXers/ Radio Hobbyists/ new comers will find tips and tricks to make and maintain Antenna’s of different types. And please don’t forget to give your feedback to elnino (at) dxinginfo.com. Your suggestions and criticisms are always welcome.
Here we firstly present RNW’s Antenna Advice – Choosing the right antenna for your receiver…Version 3.0 Editors: Jonathan Marks and Marian Meeuwissen Adapted for the World-Wide Web by Thomas R. Sundstrom as follows:
- Introduction to Antennas
- Factors That Influence Shortwave Reception
- Is An External Antenna Always Best?
- Types of Antennas
- Safety Points to Remember & Conclusion
- Further Sources of Information
At Radio Netherlands, we get several thousand questions a year about antennas. This feature is designed to explode some of the myths about antennas and offer some practical advice.
If you look at books about this subject, they quite often have a huge antenna on the front cover. This leads to the general impression that a large antenna will pick up a stronger signal and therefore give better reception of the chosen signal. In this feature we hope to show that the location and orientation of the antenna is much more important than the size. The claims that many manufacturers put in their brochures are only half the story.
We will examine the factors that influence shortwave reception, address the question of whether an external antenna will always provide better reception, discuss passive and active antennas, look at some antenna accessories and review some antenna safety tips.
Two appendices are included: a bibliography and a list of names and addresses of publishers, vendors and manufacturers. We would like to hear of your experiences. We have used our own to compile this document, together with a great deal of input from shortwave listeners around the world.
[tab: Passive Antennas]
Experimentation with antennas has existed since radio began. One of the basic antenna forms is a dipole, whose length is half that of the wavelength it is to receive. The center of the dipole is cut so that a coaxial cable can be connected. At this length the antenna impedance best matches that of the connecting cable, namely 50 ohms, and there is a maximum transfer of energy.
The dipole may be mounted horizontally, as an inverted-vee (with the center higher then the ends), or as a sloper (one end is mounted higher than the other).
Influences or Interference
Propagation, natural background noise, and man-made noise influence reception conditions. Appropriate antennas and receivers can reduce but not eliminate the effects of these factors. Let us examine these separately.
- Natural background noise
- Man-made interference
[tab: external antenna]
Will I always get better reception with an external antenna?
Is An External Antenna Always Best?
Portable radios with a built-in telescopic whip have sensitive input circuits that are carefully matched to that antenna. If you lengthen the whip (e.g. by clipping on 12 meters of wire with a crocodile clip) you may find that the radio is bursting with signals (especially after dark on the bands of 31, 41 and 49 meters). If you listen carefully, you may discover that the majority of the ‘extra’ signals you hear when the external antenna is connected are not really on the air. They are generated from inside the receiver as a result of overloading.