@Sunshine 

Thanks for email. I am not very good at these technical things but today tried the router in other areas of the house but the signal reception only gave me 2 bars, so have returned to original location. I am testing this as I have bought an extenal antenna and want to make sure it is on the best side of the  house. I have connected router to computer by  new ethernet cable and get signal strength of 100%  and down load speed of 25mbps and upload of 32mbps. The wifi connection from desktop to router gives 50% signal strength. However my mobile phone, almost new, show network speed of 390Mbps but signal strength of -109dBm 28asu. This does not allow me to listen, for instance, to the BBC programmes which I used to be able to do before switching to the MR 550. I am sure I am doing something wrong but cannot see what it is - can you help please. 

I have tried using wifi analyser and using this on my phone it says the signal strength is -29dBm but there is 90% interference and recommends using different channels but I cannot see how to do this -is this important? Thanks for any help.