Technical Articles

A Quick Guide to Dummy Loads

In an RF system, a dummy load, also known as a “dummy antenna,” is a device that simulates an electrical load, allowing Hams to accurately adjust and test their transmitters prior to hooking them up to an actual antenna. Rather than tuning up and radiating an on-air signal when attached to an antenna, a dummy load lets you avoid producing QRM that interferes with other radio transmissions—a faux pas that will certainly bring a swift rebuke from your fellow operators. Dummy loads typically consist of a resistor attached to a heat sink that dissipates power from the transmitter. Operators should choose dummy loads with similar power levels that are fed to the antenna that will be used.

 The dummy load also:

  • Prevents damage to equipment that can result when a transceiver is operated but no load (either dummy or antenna) is used
  • Allows you to make accurate adjustments to your transceiver

DX Engineering carries a range dummy loads from leading brands. Here are a few:

The 50-Ohm MFJ 264 Dummy Load works with all radios from 160 meters through 650 MHz and from QRP to the full 1,500 watt legal limit. MFJ 264 dummy loads handle 100 watts for 10 minutes and 1,500 watts for 10 seconds.

Rated from 0 to 500 MHz, the Diamond Antenna DL30 Series Compact Dummy Load is capable of 15 watts continuous power, or up to 100 watts for short periods. These units present your transmitter with a 50-ohm load and a maximum 1.15:1 SWR across their entire frequency range.

Ameritron’s ADL-1500 Dummy Load allows you to run the maximum legal limit of 1,500 watts for a full five minutes. The label on the dummy load includes a power vs. time chart so you always know how much power it can handle and for how long. The ADL-1500 comes with high-quality, industrial-grade transformer oil (containing no PCBs) and a heavy-duty 50-ohm non-inductive resistor.

Palstar’s air-cooled DL1500 1,500 Watt Dummy Load handles 100 watt “barefoot” power levels for 10 minutes and 1,500 watts for up to 10 seconds. A custom-designed hyperbolic cone permits the DL1500 to operate at up to 500 MHz, although there is some loss in power handling capability above 30 MHz.

Palstar’s DL2K 2,000 Watt Dummy Load handles 2,000 watts for one minute or 400 watts continuously.

An excellent choice for operators using a high-power amplifier, the DL2K features thermostatically-controlled fan cooling that only runs when needed, or can be switched on to run continuously.

The Vectronics DL-2500 Fan-Cooled Dry Dummy Load simulates a matched 50-ohm antenna. It delivers power dissipation of 2,500 watts average up to one minute maximum and 300 watts indefinitely.

See all available dummy loads at DXEngineering.com. Not sure what dummy load is right for your station? Contact the Elmers at DX Engineering for wise guidance.

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