Signal strength indicators

With simple receivers, tuning must be done „by ear“ for maximum volume. As early as the 1930s, signal strength was indicated by measuring instruments to facilitate tuning for radio station operators.

• Light-emitting diode / Tuning LED: simple travel portable sometimes have a small LED that lights up when a strong signal is tuned, but this is pretty useless for precise tuning.

• Magic Eye: Tubes with a green luminous screen have been used in tube radios since the forties to indicate signal strength; a radio with a „magic eye“ in the living room was the pride of family, especially in German-speaking countries.

• Signal strength meter: moving coil meters have been used to indicate signal strength since the early days of radio communications. Many multi band receivers have a signal strength meter to give it a professional touch. Cheap sets have simple instruments with, for example, a 0 - 5 scale, more expensive receivers come with an instrument displaying S-units and sometimes, these instruments are even calibrated; only with calibrated S meter, the field strength readings are usable. Many S-meters on domestic sets react much too quickly and give a false impression of the signal strength.

• Signal strength displays using LED chains or LCD bars: the quite expensive and sensitive mechanical measuring instruments have been replaced in modern receivers by chains of light-emitting diodes or a liquid crystal bar display. Also here, a properly calibrated signal strength indicator is very useful, on some semiprofessionel sets, the signal strength bars tend to over-read.