Hum or noise? Sparks? Picture moving on the screen erratically. In many cases, but not all, the root cause is divergent ground potential in the electrical systems that sums up in the multimedia set. The mains power, the TV and/or radio antenna, the internet connection do not necessarily share the common stable grounding point, hence differing ground potential. All these, let us say, electrical sub-systems differing ground potential, drives currents through the devices interconnects and add noise, hum and can cause erratic transients that will reduce system performance.
By adding an e.g. antenna ground separator, essentially a completely galvanic separation via a 1:1 transformer, this ground loop could be opened and the pure signal will only be transmitted, provided that the problem comes from the aerial sub-system.
Now, there is another condition similar to the above and that is caused by stray capacitance which emerge from electrical devices that is on one hand connected to eachother by interconnects, but connected out-of-phase to the wall socket mains power. This conditition will alsop drive a similar current as noise between the devices. Sorry to say, many are unaware about these two problems, how similar they may act and even discarded from as not applicable. Both problems are possible to reduce, or even eliminate, it takes some systematic fault tracing and some basic knowledge about electrical systems.
Begin by making sure that all your devices are connected in-phase to mains power. Contact your local hifi dealer for further support.