Hi all, I've got a Athearn RTR SW1500 that I'm struggling to set up. I won it on e-bay and it came with an NCE decoder build in. This decoder was very basic however (it was an N scale decoder to boot), and I couldn't coax any low speed performance out of it. In fact, I needed to increase the throttle when it would suddenly start to move, but not good enough for switching.  I still had a TCS T4X decoder sitting around, which I had used previously in another loco before that one was converted to a sound equiped decoder. 

So I swapped the decoder and set about tuning it. Low and behold,thanks to BEMF I can control it now on really slow speeds, but the problem is now if I accellerate. The loco speeds up , and then while the throttle increases , the loco slows down again, and somewhat mid way throttle comes to a stop. I think this is due to the BEMF changeover point, where BEMF is gradually reduced. It cannot be tuned as TCS BEMF feature is fully automatic. 

I then decided to try it without it, and experimented with the dithering function instead (various 'kick' frequency and amplitude combinations attempted) with similar results. 

Has anyone seen this kind of behaviour before, and what can be done to solve it?

Thanks very much for your tips and insights.

Koos

BTW: I'm using JMRI Decoder pro for my programming of loco's. Not that this means a lot, perhaps, but please make your reply's generic. Certain functions that might be in a Digitrax DCC controller (aside from them doing everything (addresses etc in hex) I might not be able to replicate.