Channel 4 have scheduled a change to the transponder that carries C4 HD.

The change to Channel 4 HD will occur overnight on 27th March into early hours of 28th March. Channel 4 HD will be unavailable for a maximum of 4 hours at this time, between 2300 until 0300 UK time.

Channel 4 HD is on the Astra 1N satellite at 28 degrees east, 11.126 Vertical, SR 22.000, FEC 2/3

It is reported that this outage is for “essential maintenance”, although it is speculated that this is for a change of transponder broadcast parameters, possibly to accommodate future channels operating on this frequency, like 4Seven

Update:

Channel 4 HD frequency was : 11.126 Vertical, SR 22.000, FEC 2/3

Channel 4 HD frequency is now : 11.126 Vertical, SR 22.000, FEC 5/6