How do you figure 4.1mhz is the lower part of the DCS range? The basic carrier for DCS is 3.27 mhz, but as Adrian states, it can get down to less than one mhz for some signal bursts.
TMCC really doesn't have a "top end", it's an FSK signal that is closely centered around 455khz. The modulation bit rate for TMCC/Legacy is around 3,000 BPS. You won't find it spread out like the DCS signal.
I truthfully don't have an "educated guess" on a choke that will do what you're seeking, which is why I've not responded with a suggested part. My education is telling me that it's not possible to filter out the interference while still keeping the TMCC signal. Since the TMCC signal doesn't have a wide spectrum, I feel that amplitude control is the best route to balance the TMCC and DCS operation.
