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 ;
https://gm3sek.com/2019/10/11/clean-up-your-shack-2019/
https://www.youtube.com/watch?v=LSL1h6MJbaI
http://www.m0nwk.co.uk/mains-electricity-filter-for-emc-noise-reduction/
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
| Part | Ref | Source | Price (2020) |
| 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 |
222-412 |
https://uk.rs-online.com/web/p/standard-terminal-blocks/7581650/ |
£4 |
| 2.5mm Ring Main Cable @ 1m | Require 2 x 1m length (Twin and an insulated conductor as earth) | £1 | |
| IP65 Enclosure | GR17020 | https://cpc.farnell.com/ce-tek/gr17020/abs-enclosure-240x190x95mm-ip65/dp/EN84549?st=ip65%20abs%20enclosures | £15 |
| IP68 Cable Glands x 2 |
https://uk.rs-online.com/web/p/cable-glands/8829941/ | £1 | |
| 4w extension cable | https://cpc.farnell.com/brennenstuhl/1150403/4-way-switched-extension-lead/dp/PL03184?ost=pl03184 | £5 | |
| Warning Sticker | e-bay | £2 | |
| Sundries | Glue Gun, Cable ties, Push on Terminals, Earth Sleeve | - |