Many of us have come across TVI at sometime. The lucky ones have their neighbour come knocking on the door, and the less fortunate, get a visit from the OFTA radio inspector!
When you have this problem, something is not right and you need to fix it soon. No good saying, it must be the TV that is at fault! Although you might be correct in saying so, there is a lot that we can do to prevent this from happening in the first place.
If you do not cause TVI on your own TV, there is a good possibility that it is not your fault. If that is the case, well then you have the opportunity to still help your neighbour solve his problem!
But first, let us look at some of the causes of television interference.
Here are some tests you can do to find the cause:
1. Check the VSWR of your antenna, which should be carried out each time you are about to operate. But watch it! Sometimes the fault can be intermitting because of a bad connection somewhere on your feedline. Check for corrosion in cable and connections. Fit RF choke and Low Pass filter.
2. Try using a different power supply, such as a battery. There is always the possibility of RF feedback through the mains power line. Fit mains RF filter and ferrite rings to power cables.
3. Check all plugs for poor soldering or corrosion and look for moisture in the cable. Water or moisture in coaxial cable is one of the most common causes of TVI. Your VSWR meter reading might even give you quite a normal reading, so be sure to open up your connecting plugs and check.
4. Get rid of the rat's nest of wires behind your radios. Keep all connecting cables as short as possible.
5. Use High Pass filter on TV receiver. High-pass filters are cheap to buy or you can make your own. And it would be wise to give that neighbour a call and put one on his TV. Believe me, having good neighbours is most important to any radio operator!
I made a lot of this High Pass Filter and install at my neighbour's TV, the performance is outstanding. They are all happy with it.