Whilst on Radio 5 live 909 I loose the volume on my radio.

What might be causing it?

It occures from time to time and has occured over the past year although is becoming more persistant over the past week.

It happened on Weds 1 Oct (at night), Tues 6 Oct and weds 7 Oct (21 times).

the volume attenuates for about 10 - 100 meters at anyone time and not in any spacific areas.