Well, I suppose it was worth a try with the v8.07 DMT Tool -- but the 'bit allocation not available' says it for me: it's not going to help. Sorry!
LW radio: if you de-tune your receiver from (say) R4 on 198, you should simply hear a hissing noise. If there's something generating RF interference, you'll hear an unmistakeable crackling hum, totally distinct from the 'de-tuned' hissing. However, upwards of 150kHz is taking you outside the suspect range, anyway.
Below 150kHz there are some defined bands for amateur radio operators (hams), plus a number of bands reserved for maritime navigational aids (Decca, LORAN). So /if/ there is low-frequency interference hitting your upstream bandwidth, it might be because one of your neighbours is a ham radio operator... or perhaps there's a Decca or LORAN transmitter down the road (unlikely unless you're pretty near the coast)?
I'm rambling now, so I'll stop.
Rom