Dummy load

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Cantenna dummy load suitable up to 30 MHz and up to 1 KW
Cantenna dummy load suitable up to 30 MHz and up to 1 KW

A dummy load is a device used to simulate an electrical load, usually for testing purposes.

Contents

[edit] Radio

In radio this device is also known as a dummy antenna or a radio frequency termination, is a device used in place of an antenna to aid in testing a radio transmitter. It is substituted for the antenna while adjusting the transmitter, so that the transmitter does not interfere with other radio transmitters during the adjustments. [1] If a transmitter is tested without a load, such as an antenna or a dummy load, the transmitter could be damaged. Also, if a transmitter is adjusted without a load, it will operate differently than with the load, and the adjustments may be incorrect.

The dummy load ordinarily should be a pure resistance; the amount of resistance should be the same as the impedance of the antenna or transmission line that is used with the transmitter (usually 50Ω or 75Ω).[2] The radio energy that is absorbed by the dummy load is converted to heat. A dummy load must be chosen or designed to tolerate the amount of power that can be delivered by the transmitter. [3]

The ideal dummy load provides a standing wave ratio (SWR) of 1:1 at the given impedance.

See also: Antenna (radio) and Standing wave ratio

[edit] Audio

When testing audio amplifiers, it is common the replace the loudspeaker with a dummy load, so that the amplifier's handling of large power levels can be tested without actually producing intense sound. The simplest is a resistor bank to simulate the voice coil's resistance.

For loudspeaker simulation, a more complex network is more accurate, however, as actual loudspeakers are reactive and non-linear. There are many designs for loudspeaker simulators, which emphasize different characteristics of the actual speaker, such as the voice coil's inductance, mechanical suspension compliance, and cone mass.

See also: Thiele/Small and Electrical characteristics of a dynamic loudspeaker

[edit] Power supplies

There are also dummy loads for power supplies, known as load banks.

[edit] References

  1. ^ (1990) in Kleinschmidt, Kirk: ARRL Handbook for the Radio Amateur. Newington, Connecticut: American Radio Relay League, 25-21 through 25-23. 
  2. ^ (1990) in Kleinschmidt, Kirk: ARRL Handbook for the Radio Amateur. Newington, Connecticut: American Radio Relay League, 25-21. 
  3. ^ (1990) in Kleinschmidt, Kirk: ARRL Handbook for the Radio Amateur. Newington, Connecticut: American Radio Relay League, 34-22 through 34-28. 

[edit] See also

[edit] External links

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