On Thursday, October 6, 2016 at 8:41:04 PM UTC+3, wrote:
I've had a similar problem from time to time with my FSG-50, every now and then a burst of noise. Eventually I realized it was only happening in the circuit for runway 25 at my home base, at about 2/3 of the way on the downwind leg. It hasn't happened this year so all I can thin of is that there may have been some equipment at the storage and construction yard beneath the downwind that was putting out electromagnetic interference.

Sometime in 1990 or 1991 I noticed that when I was speaking on the phone in my new flat in Newlands, Wellington there would sometimes be a "bzzzt" audible every four or five seconds. It seemed to happen more on rainy days.

One day I was gazing out the window while on the phone (the clouds can't have been all that low, or the rain heavy) This is something like the view. I was in the brick house on the left.

https://goo.gl/maps/r5WKiyG2RRA2

I noticed the bzzzt was happening in synchronization with the rotation of the big FO primary radar on Hawkins Hill 13.6 km away!