Electromagnetic interference is something we all experience from time to time.

From a hiss on the phone to the fuzzy lines on an analogue TV during a thunderstorm, EMI (as it is known) gets everywhere.  

When it comes to the sensitive electrical components on military jets, this interference - which is created by the electromagnetic signals manmade or from naturally occurring sources - can be more than just annoying.

“Modern aircraft use sensors that send signals to the control systems that are vital to the safety and functionality of the aircraft,” said Mark Johnson, EMI business lead at Oxley Group, in Ulverston. 

“These signals from the sensors are protected by the filtering diverting away high frequency interference, ensuring the data is clear and accurate.

"The effect of not having adequate filtering varies from a poor display in the cockpit, right down to some systems shutting down. It can be quite serious.” 

Oxley has been manufacturing and developing EMI filters since it was first founded in 1942 by Freddy Oxley, who made the components for the RAF during World War Two.

Today, as well as military and commercial aircraft - including the Airbus A320, the world’s highest selling airliner - Oxley’s EMI filters are in use on everything from oil platforms to trains, rifles and land-based vehicles. 

“Wherever there’s a signal that needs to be protected they can be put to use,” said Mark. 

In many cases, Oxley will have to make customised parts for specific applications. The process of designing and making an EMI filter is complex. Around 20 stages are involved in the manufacturing process; they are then subjected to rigorous testing to ensure they meet the necessary standards.

Oxley manages all of this end to end from the Ulverston site. Manufacturing takes place by hand, as well as with automation where machine precision is required.

“Some operations are automated but there are also some skills which you just cannot automate,” said Mark.  

Precision technical ceramics play a key part in filtering out interference and Oxley has a dedicated in-house ceramics facility. “The whole process is all about making sure that the parts come out perfectly,” said Jayne Moorby, head of marketing at Oxley.

“EMI filters play such a vital role and they really are everywhere, but most people don’t even appreciate they exist and that so many of them are made here in Cumbria.”