Radio specifications

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 :

1. Sensitivity - the ability to receive weak signals

2. Selectivity - the ability to distinguish between signals separated by a small frequency difference

3. 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 and for this reason the following recommendations should provide some guidance.

1. 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.)

2. Spreading the bands out is particularly useful on short wave. Many radios now on the market try to cover all of the meter bands into the space of say seven or eight centimeters on the radio dial. This reduces the effective width of any one meter band to a half a centimeter or even less. Fifteen or more stations may be operating on this band, which means that tuning 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. It is not a powerful output and a large loudspeaker that count.

All radios have a circuit called an automatic volume control. The purpose of it 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 that a weak station. This is why a strong station sounds much nicer. There are then two ways to improve reception - one way is to decrease the amount of noise, the other is to increase the strength of the signal with a good antenna.