I was watching a video from Callum the DX Commander on his YouTube channel earlier today. Callum was doing a poor job of explaining why he runs his rigs with wide open filters. He explained how the best filter for QRM (in his opinion) is his brain. Actually that’s something I can agree with in part, but it’s not the entire story.
If we are talking about having the filters open while listening to various stations a few kilohertz up and down the band, sure open filters are fine for an experienced operator (until operator fatigue starts setting in). Unfortunately not every station has a phased array, stacked yagis, a 400w amplifier and a big signal.
I reminded Callum that QRP or weak stations down in the noise, or buried in the QRM from “big gun” stations won’t be heard when filters are wide open. I also mentioned how weak signal field operators are very appreciative of operators who go the extra mile to bring them out of the noise. That’s when the sarcasm started. Callum (in good fun) suggested being too lazy or couldn’t be bothered with a “non-existent” station down in the noise. Enter the Contester Mentality.
More often than not contesters pass up weak stations, in favour of another easy to copy big gun station. The question is why. Well there’s no Sinister plot against the weak signal stations, and what Callum is saying in his video gives us pretty good answer. With the filters wide open, that big gun station simply can’t hear you, isn’t trying to hear you, and only interested in logging the next station. If you make it through the QRM or above the noise floor, then managed to bust the pile up, you’ll be in the log book. If you can’t, you won’t. Contested Mentality.
Let’s think about the job of our filters. First of all our filters allow us to isolate the area of the band where we’re working. If we apply our filters correctly, we block out unwanted QRM from stations on a adjacent frequency. More importantly when filters are applied correctly, those weak signals often come up above the noise floor, making them perfectly readable, to an otherwise deaf station (running open filters). Filters allow us to hear what we want to hear, and block what we don’t. This makes whatever is left inside our passband much more readable. Naturally we open the filters when we’re searching for band activity, but when sitting on a frequency activating for whatever reason, tighten those filters up to hear only what we want to hear, where we want to hear it.
If you use your filters correctly, you allow your radio to hear things that you would not otherwise have heard. Don’t take my word for it, just try it!