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There are many discussions on radio forums regarding broadband qrm/n. Most of the time the blame is put on wireless devices and/or neighbours without first looking closer to home,and often before any investigation has been done. Background noise levels of S7 upwards are not uncommon for many people suffering this problem.This is simply a quick guide to things that can be done before looking outside the home as often your background noise can be dropped quite a lot by making sure your own devices in the home are not to blame. You may be suprised at just how much qrm you generate yourself.
Rf earth
This gets overlooked quite a lot and if done correctly can prevent lots of problems. Having your radio equipment set up correctly can save problems down the line . You will notice most equipment has earth lugs on the rear of the device.These are here for a reason yet many peole simple don't use them. Your radio equipment should have a good RF earth system fitted regardless of antenna used. This really shouldn't be simply the nearest water pipe but if possible good earth straps connecting the radio,atu ect to an earth rod outside ( earth straps can be expensive so i use the braid from old coax. its easy to remove and cheap). From there putting as much wire in or on the ground as possible. Earthing the ground side of the antenna or fitting a lightning arrestor well earthed will help with noise levels and help prevent static build up. Fitting ferrite rings on power leads is also a good idea and can prevent problems ,Again this is just a simple guide and there is a load of information on the net regarding earthing,bonding ect.
Is it coming from your home?
First thing to do is note the times of interference.Does it have a pattern? For example is it worse at certain times of the day than others? Is it worse when the kids come home from school? or when the soaps are on. Is it broadband or segments of a band ?This information can help find the source.Here is a quick test to see if that qrm is coming from your own home. Turn the radio on WITHOUT the antenna connected. If the noise drops off and there is nothing on the meter the chances are the qrm is airbourn.(This doesn't mean its not coming from your home). If the noise is still there the chances are its coming through the house wiring or power supply .First get yourself a battery capable of running your radio.
Now go to the electric consumer unit and turn the mains off. Turn each trip switch off too. Next go round the house and turn every electrical device off,unplug and switch the sockets off also.
Now check the signal on the radio (Antenna connected)using the battery as power. Has it improved at all ? ,if so then some of your problem may well be from yourself.
Turn on the power for the plug sockets in the home and turn on each socket in turn without anything plugged into it.(check your signal at each plug socket turned on). Now turn on each piece of electrical equipment one at a time looking for signal changes as you do it. You will instantly know when/if you come across an offending appliance.Work through the electrical system using the same method checking everything in turn. Its quite easy to pin it down if there is something in the home causing the problem. I have a portable tv in the spare bedroom that when turned on can turn my background level from an S3 to S9.
Once you have done these checks hopefully you will of found the offending appliances. Check everything, pc monitors if near radio equipment can be troublesome which more and more people are having sat on the bench next to them.
This is a simple guide which doesn't take long and can resolve many problems without leaving the house or resorting to spending money or worse still leaving the hobby because of it.There is lots of more detailed information on the net regarding all aspects of noise pollution so this is put here as a starting point. I hope this has helped anyone suffering qrm.
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