Your discussion about the "new" models prompted me to check my PL-380 that I received from Anon in mid December. The serial number is:
3692009 000333 Mfg Date 11 09
It has 2 screws in the battery compartment. WIthnthe DSP set to 1 khz. and tuning slowly in 1 khz. Steps (I used 1310 khz which has no local) stations I did notice that the RX audio did seem to drop but did not disappear completely. This was done using only the stock loop stick and sitting in the living room. I live in a rural setting and have no interfence unless it is "house" generated. In fact the radio is within 12 inches of an HP 22 inch LCD Monitor and no noise from that source. Right now I'm listening to a Spanish station I will try and ID later.
As far as SW and LW I haven't tried yet.
Hope this helps a little.