It only affects TVs which are connected to a SKY box via TV coax, often there is also an amplifier involved although this usually goes unnoticed as it's normally tucked away in the loft.
This type of interference which are sometimes referred to as "buzz bars" are frequently accompanied with a crackling / spluttering sound with the bars running horizontally across the screen and it can last from just a split second to as much as two or three seconds at a time.
Many people report that the interference is worse in the evening and although there is a chance that this could be true it's more than likely that more TV viewing is done in the evening so it's more noticeable problem during peak viewing times.
With the roll out and upgrade of many mobile phone transmitters to 4G this interference is becoming more and more common, and it's 4G which is to blame!
Prior to 2014 there were millions of SKY boxes manufactured and sold with their modulators set to RF Ch 68 and if you've had secondary TV/s connected to your SKY box there is a reasonable chance that the factory default frequency setting of Ch 68 has not been changed, even if it has been altered there is still a good chance that its been moved to either Ch 67 or 69, unfortunately any RF output channel which is used from around Ch 55 and up is susceptible to this type of 4G interference so I guess that there are many, many thousands of people throughout the country which are affected.
One good thing is that this type of interference is normally easily cured.
If you're competent enough to alter the SKY boxes RF frequency then I would still suggest you give me a quick call and let me know which terrestrial TV transmitter your TV Aerial is pointing at and I will advise you as to the best RF Ch number to use.
If you chance it and go it alone there is a possibility that you will wipe out a group of Digital TV channels if you guess and choose a random RF number.
If what I've written above all sounds to complicated then just give me a call as I'm more than happy to talk anyone through the simple process of altering the SKY boxes RF setting, over the phone....free of charge!
Please note - The new SKY Q system is not affected by 4G interference, also most SKY boxes manufactured and sold after 2014 have had part of their modulators removed making it more difficult (but not impossible) to watch SKY on secondary TVs, consequently there's less chance of 4G interference.