I bet your using a Vbox ?
If you are its experiencing interference at certain frequecies due to inadequate sheilding around the power supply and LNB cable inputs, usually around 11680 in the low band and 12430 in the high band, give or take a few hundred MHZ either way. It wont just be 30W either, it will also happen on other sats too around these frequencies, youve just not noticed yet. This can be caused by a nearby DECT phone , either your own or next doors. I had this issue too and the only solution I found was to wrap the Vbox in tin foil. It wasnt practical for me to move the Vbox somewhere else in the house and I do not have a DECT phone to move elsewhere, but moving the Vbox would probably have worked too.
If you have a DECT phone then just move that away from the Vbox, if not try the tin foil, it really does work.
If you can be bothered make a Faraday cage for the Vbox, this would be by far the best solution, but might be a bit expensive, if you were to buy a ready made one rather than making one yourself. Other than that your only solution is to buy a new Vbox with better sheilding, but finding new gear for those of us using proper dishes and mounts is getting harder and harder so the prices have rocketed.