Hi Richard,

 

      Upgrade IF filters to improve selectivity must be designed for the Ultralight radio's actual IF, which is 450 kHz for the DT-400W and most other Ultralights.  There is a limited selection of 450 kHz upgrade filters, some of which could improve upon the stock DT-400W's selectivity.  Guy Atkins (a local Puyallup, WA resident with extensive IF filter experience) designed a modification last spring for the DT-200VX, which improved upon the stock selectivity significantly.  The same Murata 4-pole (I believe) 450 kHz filter would also improve the DT-400W's selectivity. But none of the 450 kHz IF filters would be nearly so effective as the 455 kHz IF filter we three (John, Guy and myself) have installed into the E100, according to Guy.

 

     Upgraded IF filters, by themselves, provide selectivity improvements, but usually no benefit in signal- pulling power.  Larger and more effective loopsticks, by themseleves, provide great increases in sensitivity, but no benefit in selectivity.  But when they are combined together, the DX effectiveness is overwhelming, such as in the modified E100 that John, Guy and I are using.  The E100's 455 kHz IF made it possible for Guy to choose an extremely effective Murata filter (the same one used in the Eton E1).  The experimental invention of the "Slider" loopstick happened about the same time, making the E100 ultra-sensitive.  Full articles about this "wildcat" E100 will appear shortly in the AM-DX club bulletins.  My own model has logged 30 TP stations in only three months, before the DX season even starts.  We hope you all will have so much fun!

 

     73,  Gary