Tuesday, April 4, 2017

QRM/QRN interference

We radioamateurs investigate the radio spectrum, we experiment we listen to others trying to get a signal out. But if you live in a dense populated area like most of people do in the Netherlands it can be hard. PE1BVQ Hans wrote me he has seen some of my videos and it occured to him I had much less interference as he has at home. He wondered he had something wrong with his antenna, using a shortened endfed in sloper configuration. Well, I decided to make a "interference" video on my QTH. I live at a rural area with free sight to the north and to the south. Nearest neighbours are 20-30m from my vertical antenna. I decided to leave ATT, AGC and all filtering off. However it's just a video shot at a certain moment of the day. Interference is different from time to time and from day to day, at least at my QTH. Below a video from daylight situation.

Remember, this is without any attenuation or filtering. Just normal receive without any help. Although in the video you will see I do a short test on 80m and 60m to show the effect of the filters.
I can choose between ATT on/off, DSP ANF on/off, DSP NR on/off, filtering 1,9KHz SSB on/off. Normally with ATT and 1,9KHz filter on I have a noisefloor of S0 on 160/80/60/40m. Without you can see in the video about S7. From 20m and higher it is lower, although it actually depends on time of day and propagation. Below a video from darkeness situation early in the evening.

QRM on 160m is much higher now. Rest of the bands are equal I think, Except for 17m which shows higher QRM. This happens sometimes on 20m and 17m, not always on the same time. But most of the evenings I have a much higher noisefloor on 20m/17m about S3-5.

When I look and listen to the videos I think it is amazing I can actually hear weak signals. Filtering helps a lot. And am I on a quiet location with a low noisefloor? I really don't know as I cannot compare. I think if you still have S7 noise with attenuation on you have a big problem....I can hardly imagine such a bad situation. But if you live in a big city here in the Netherlands (or anywere else)  it could be....


  1. You could visit my house in Utrecht. Currently S8 noise is 'normal' on 40/20/10 meters. Real wideband noise, the type that's really hard to find a cause for. I've been in touch with AT who said they can only work with specific complaints ('frequency X has interference at level Y from orientation Z') and that 'high noise floor' is difficult for them to do anything about.

    1. Yes Koos, in a big city this is a major problem. 73, Bas


Thanks for your comment. Bedankt voor je reactie. 73, Bas