Combating Interference: From AC and Antenna

By Non-dropframeDepending on the type of rig you’re working with, interference from antennas or the AC line are likely degrading signal strength. While U.S. and international Hams face different interference challenges based on their hardware, man-made noise, the electrical grid and more, I wanted to share my experience using a piece of power management equipment typically suited for high-end audio gear.  In addition to being a UK-based operator, I’m also an “audiophile,” which led to this experiment.

Recently, I decided to try a power management device designed to provide, component level filtering and protection to any AV system, on my HF transceiver, a top of the range Japan Radio Company JST-245 just to see what effect it had on the noise floor which has been increasing bit by bit every year.

Suffice to say the product lowered the noise floor from a constant S4 to an acceptable S1-S2 on the rigs meter. I was amazed and replaced the standard JRC kettle IEC several times with and without the product in line, and the same results came back every time when the piece was in the chain. My experiment was on 28.535 MHz where I normally work DX on the 10 meters.

These measurements show how dirty the mains are (at least in the UK) since you could actually see the reduction on the rigs meter. It’s worth noting that my AC power is fed through overhead lines, and not underground as with many modern homes, which likely adds interference. But with many UK and international hams lamenting the rising levels of QRM, in my experience, electrical main noise is the biggest culprit.

From what I understand, interference in the U.S. and internationally is driven by the antenna side of the receivers and not through the AC side. I also understand that a high percentage of ham radio transceivers used by hams worldwide have external DC power supplies that are usually well filtered, and wouldn’t require an external AC line filter since they feed the radios directly with 12 -14 volts DC. However, based on this, I’d say any international ham operator with an internal AC power supply (like mine) could benefit from an external power filter.

I know many new radios feature advanced DSP filtering/processing, but hearing the difference this product made inspired me to share my experience. One last cool thing is that the power unit also acts as a under/overvoltage protector which adds a layer of safety while protecting expensive investments from power surges, sags and spikes.

Now, to find a solution for filtering the RF signal before it reaches the radio antenna.

Rick, MØOPR, is a special contributor to and writes from Bristol, UK.

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