Report on Widespread QRM in East Preston and Area, West Sussex.
By Peter Dodd, G3LDO. 24th August 2005.
The interference was first noticed about two years ago and it appears to be getting steadily worse.
It comprises a spiky broadband repetitive signal centred around the 14MHz band, although as it gets worse it is affecting adjacent bands of 10 and 18MHz. An audible example of the interference can be heard by clicking LDOqrm14AM2.wav.
This signal in is recorded with the receiver tuned to 14.11MHz set on AM mode with the AGC turned off. The signal strength on the peaks of pulses is four S points (24dBs) above ambient noise. The .wav file is just over a Mb.The local source of the signal at this QTH seems to come from a telephone distribution pole located about 200m to the south. It can be minimised by rotating the beam so that the side minimum of the pattern is facing the telephone pole. However, the QRM appears to have many sources, spread over a wide area.
The map, given below, shows the hot spots of QRM, marked in red. A local radio amateur, G3CCX, who used to work exclusively on 14 MHz has now moved from the band and changed his monoband 14MHz antenna for a higher band antenna. He had severe QRM of the same type from a nearby telephone distribution pole.
I have investigated sources of this QRM and there appears to be hot spots that don't seem to relate to anything. There are no overhead telephone distribution wires in the centre of the map near the letters BN16. This interference occurs in other areas outside the boundaries of this map. I have detected it as far to the west at Littlehampton and as far east as Kingston Gorse.
About a year ago I reported the interference to BT and a team came out from a depot in Bristol and spent the best part of a day here. This was done just before the service was closed down. They were unable to identify the cause of the interference but thought they had found the source. They disconnected the power to one residence where the interference level was high and QRM disappeared. They came back to check with me but the interference level was just the same.