19 Sep Local Radio Interference
Last Updated on September 29, 2022
Local Radio Interference – know where to look in your own home
Interference. It’s the bane of the Radio Amateur’s life.
There are two types – one you can’t do much about such as power line interference and the neighbour’s solar installation, and one you can do something about – local interference, such as dodgy battery chargers and cheap and nasty LED lighting.
LEDs are really good for the environment. They can last for years which means their carbon footprint is minimal compared to other forms of lighting. They’re also low voltage which is a big advantage for consumers.
One of the most overlooked sources of interference to the radio spectrum is right under our noses. It’s rather obvious, but the LED lighting in the shack, or on the table next to your favourite transceiver is quite often the source of your noise.
There are many retailers who unknowingly or maybe knowingly sell lighting solutions that cause EMI. With radios such as the IC-7300 and the IC-9700 that features a spectrum waterfall display, noise from any source is easily spotted.
I have a few LED lights in the shack that create havoc on 6m but are seemingly quiet on other bands. These lamps are Harte Work Lamps from Ikea.
The LED lights in the ceiling can also be a big noise emitter. I recently had all the LED lights in the house replaced with quality LED downlights that comply with our local standards. These old downlights lifted the noise floor on 2m to a point that hearing some weak signals and beacons impossible.
If you turn off everything other than your radios in the shack does the interference disappear? If so finding the culprit is quite easy. Turn on lights and appliances one by one and see if the noise returns. Chances are it’s a light or a battery charger, or maybe even a switched-mode power supply on the workbench. When it comes to lighting, try swapping out the low-voltage PSU. You may find it’s the culprit – not the LEDs themselves. Check your outside lights too.
There are many other ways to track down interference and it’s worth reading an article called “How’s your noise floor” by Bob Tait VK3XP. In this article, Bob describes some of the more complex methods of finding local radio interference involving receivers such as the good old trannie or AM radios. QRM.guru also has plans to build a DF loop which every shack should have when investigations need to extend beyond the property.
LED lights aren’t the only culprits though. Switching power supplies such as plug packs and eBay buck converters can cause grief. Poorly terminated LAN cables, cheap network routers, computers, as well as automotive batteries and power tool chargers also generate unwanted signals on many the bands. Even cheap set-top boxes and masthead tv amplifiers are notorious sources of interference.
There are enough sources of EMI beyond our control so when it comes to locally generated in your home, buy the best quality products you can afford from a reputable seller. That way you can return them if they generate signals where they shouldn’t.