GPS-savvy walkers strapping on their hiking footwear for a trek in the Brecon Beacons over the coming weeks are likely to find their signals affected by a military radio jamming exercise.

Those who use GPS to navigate their way up hill and down dale will be interested to know that telecommunications regulator Ofcom has said that jamming signals will be broadcast toward the north of the national park between May 31st and June 10th, outdoors website Grough.co.uk reports.

Running periodically from 09:00 BST to 17:00 BST in an area around the Sennybridge Training site, the operation will involve multiple jammers operating within five kilometres of Dixies Corner.

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

So if you were planning on a trip to the Brecons and were thinking of taking along your GPS – better throw the old map and compass in your daysacks too – but you already knew that, of course.