Radio Specifications

Posted in Technical Information

TWR Transmitter Building

What to look for when buying a short wave radio?

The satisfactory reception of TWR places several demands on the radio used. While it is certainly possible to hear the programmes on most receivers, some special features are desirable to facilitate reception. A suitable radio should therefore possess certain qualities best summarized as follows :

  • Listening to the radioSensitivity - the ability to receive weak signals.
  • Selectivity - the ability to distinguish between signals separated by a small frequency difference.
  • Stability - the ability to stay on a signal under variations of signal strength, changes in temperature, or vibration etc.

While most radios do indeed possess these qualities, this cannot be taken for granted. For this reason the following recommendations should provide some guidance.

  1. The frequency range of a radio which has short wave bands does not necessarily imply it covers the relevant bands. Make sure that the radio provides for reception on the short wave bands used by TWR. . (See our broadcast bands)
  2. Spreading the bands out is particularly useful on short wave. Many radios currently on the market try to cover all of the meter bands in the space of seven or eight centimeters on the radio dial. This reduces the effective width of any one meter band to half a centimeter or even less. Fifteen or more stations may be operating on this band, which means that tuning into a particular station on such a radio may be difficult. Try to locate a radio that spreads individual bands over a wide space on the dial. Some radios provide separate tuning for each of the short wave broadcast bands.
  3. Fine tuning is often included by many manufacturers on their radios to compensate for the crowded conditions of short wave. Rough tuning is done on the main tuning control and fine adjustments are then completed on this control.
  4. Many short wave receivers are not sensitive enough. Finding a radio that uses a large number of transistors and/or integrated circuits in its design will help ensure satisfactory reception. A radio having a powerful output and a large loudspeaker are not indicators of good reception.

All radios have a built-in automatic volume control. Its purpose is to give a reasonably consistent sound with varying strengths of the stations. A strong transmission along with any noise needs to be amplified less than a weak station. This is why a strong station sounds much clearer. Thus there are two ways to improve reception: decrease the amount of noise, or increase the strength of the signal with a good antenna.