GPS devices will be affected by the jamming exercises

Walkers using GPS devices are being warned of a military radio jamming exercise that is likely to affect their signals.

Ofcom, the Government’s telecommunications regulator, said jamming signals will be broadcast between 31 May and 10 June in an area north of the Brecon Beacons national park.

The exercise will take place periodically from 9am to 5pm in the area around the Sennybridge Training Area and will involve multiple jammers operating within 5km (2¾ miles) of Dixies Corner.

The Ministry of Defence said land-based GPS receivers, such as those carried by walkers, runners and mountain bikers, would be affected if in line of sight of the jammers.

There are several rights of way on hill and forest tracks in the area, on the Mynydd Bwlch-y-Groes.