Dig this test: There is a unique reason for needing a preselector on the Mercury receiver. At night, with the triple 40M Yagi stack connected to Mercury listening Europe on 20M, the ADC goes into overload. The noise floor goes up at least 25db. There are SW BC images all over the 20M band from 40M. This is at night when the SW BC sigs are crushing, of course, and during the day it is quiet. This is with Mercury's preamp on. The same thing happens on the higher bands, 10-15M too.
This is a VERY demanding test, of course, with BC signals 60+ over. But there is still some SW 40M BC stuff in there when using the 20M stack, though very weak. The preselector would probably cure this completely. I think the existing Merc front end (as little as there is) is right on the brink and could be improved, especially when the Merc's preamp needs to be on for 10-20M..
With the same test, my own FT-1000D does NOT have 40M BC images on 10-20M listening on the 40M stack at night. Huge difference.
I'm not complaining - just pointing out that a preselector is a very good investment for the Merc.
I got an email from a guy who said the UK preselctor we discussed will fit the Merc to a "T".
http://www.herostechnology.co.uk/pages/tiny_SCR_preselector.htmlT