The atmospheric conditions can distort or prevent reception of Freeview and radio - both analogue and digital.
Reports from the past 48 hours indicate that parts of England have been particularly prone to reception problems, which on digital TV and DAB digital radio can cause drop-outs or complete loss of signal on either some or all stations.
Currently, high pressure is causing a temperature inversion - where, for example, the temperature on the tops of mountains is warmer than down below - the other way around from the normal situation. This provides the ideal conditions for reception problems as a result of the radiowaves being refracted in a process known as "tropospheric ducting".
High gain TV aerials, some of which were installed before digital switchover when the Freeview signal was transmitted at much lower power levels, are more prone to pick up interfering signals on the same frequency from more distant transmitters. In exceptionally bad conditions, so-called "co-channel interference" can be observed on standard and indoor aerials.
Viewers are advised to avoid retuning, as this will cause the loss of their existing channel list. A retune may result in fewer channels being stored, or additional stations from outside the local area (even from abroad) being added to the channel list, which will disappear when conditions return to normal.
The Radio and TV Investigation Service provides viewers with advice on what to do if they encounter reception problems, and if any work is taking place at local transmitters, which may impact reception.
There is little to be done about the conditions affecting reception until the weather changes.
Friday 14/3 and atmospheric conditions are enabling reception of French TV in parts of the Greater London area, notably for those viewers whose aerials point in a south/south east direction.
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