GORDO’S SHORT CIRCUITS

When broadband noise creeps into your radio system, there are two more-common local noises you may encounter. By “local,” I mean your house or your neighborhood.

QRM Reduction Starts at Home

On 2 meters, the newest noise you see on your FM rig’s S-meter may be interference from light emitting diode (LED) light bulbs right in your own house (Photo A). On weak stations, it is the background noise that makes them hard to hear when nearby ceiling or lamp LED lights are on.

This noise peaks around 150 MHz, and goes about 20 MHz either side, affecting our 2-meter band. The LED noise usually does not affect the HF, or high frequency, bands (3-30 MHz).

This noise is not generated by the LED itself, but by the “chopper” switcher innards taking 110-volt AC down to a much smaller voltage to make the individual LED illuminate. The dimmer function on some LED modules (Photo B) is the noisiest, especially in the mid-dimmer setting.

Try this — tune your 2-meter rig to a distant weather station