A large proportion of interference on 160, 80 and 40m bands seemed to be local switched mode power supplies, motors and motor controllers, so I set about looking at projects had already been worked on. I didn't have to look much further than the work by GM3SEK on his Clean up your Shack presentations, links below ;
I built this based on the above information sources, and assembled with the parts listed (Links and Prices correct as of 1/12/2020)
Total build cost, £75 plus 2 build hours.
Could be cheaper by replacing the RFI filter with a single stage item, which would be £15 less.
My Mains Filter
Picture of the Mains Filter, completed in a suitably sized IP65 enclosure
Picture of completed enclosure and 4w power cable
Mains Filter Parts and Sources
|Schaffner Chassis Mount RFI Filter||FN2090-16-06||https://uk.rs-online.com/web/p/power-line-filters/1704906/||£33|
|Fair-Rite Openable Ferrite Sleeve||0431177081||https://uk.rs-online.com/web/p/ferrite-sleeves/4669164/||£14|
20A Screw Terminal Blocks or Wago Terminal Blocks
|2.5mm Ring Main Cable @ 1m||Require 2 x 1m length (Twin and an insulated conductor as earth)||£1|
|IP68 Cable Glands
|4w extension cable||https://cpc.farnell.com/brennenstuhl/1150403/4-way-switched-extension-lead/dp/PL03184?ost=pl03184||£5|
|Sundries||Glue Gun, Cable ties, Push on Terminals, Earth Sleeve||-|