Help & Advice

Hi Jakub,
At home, I have a couple of issues on the lower HF bands - There is a plasma/switch-mode sproggy around 14.220 that is more/less 24/7. Our 42" TV does cause 1 minor sproggy on 40m and a bit more than I'd like on 80m.

Interestingly, the PSU for my Samsung S22B150 monitor can raise the noise-floor on 40m in some situations. I was plagued by a neighbour's WiFi router earlier this year - but that was a few choice frequencies as opposed to wide QRM.

Do you suffer from just a high noise-floor or are there noises/blips, too? The first thing to do is to remove your own electrical items from the equation - Run your radio off a 12v battery and isolate your mains supply. If things get very quiet then you've got some "nasty" power-supplies to identify (and replace) :)

Hi Jakub

Note, my radios are all Yaesu so the features described may be different on your radio. Also, this post is about my personal and very limited experience. I don't claim to be an expert :)

The most frequent situation I deal with is high noise-floor on the lower bands. Sometimes up to S9 :( In this situation, the first thing I use is my receiver's attenuator. I keep attenuating until the signal drops below about S3. Because this is right on the front end of the receiver, it should have a positive effect on all other controls, including AGC. I also ensure that my pre-amplifier is off for all lower-band HF work, by default.

Filters: I have roofing filters on the first IF. These are good where there is high QRM, although I work CW normally and the filter is automatically at it's narrowest (300Hz). For SSB, you can use narrower-than-standard roofing filters under heavy nose situations. The operation of the other down-stream controls, such as AGC and 2nd IF filters should be improved.

Once, I had some QRM from power tools being used nearby. The Noise Blanker helped. It is the only time I have benefited from this feature.

For adjacent channel QRM my narrow filters and the IF Shift feature works well. So, I can have a strong signal from one or more stations close by, but still copy my contact with the pass-band shifted slightly up or down.

There is a Digital Nose Reduction feature on my radio, for SSB. It's very impressive and 'magically' reduces the noise floor on SSB by a high degree. I don't use SSB often enough to say how good it is in real life operating conditions or how it compares with attenuating the signal manually.... but it seems to work very well. I know you can get DNR systems off the shelf, from places like W&S.

Hope this helps a little.
Cheers
Rob M0KCP