megan,
The McMurdo NBD was still transmitting despite being listed as out of service. There was no DME, but there was a TACAN. However the crew never received a signal from that NAVAID. They could also only communicate via HF radio and were never radar identified.
Why?
NDBs, TACANs, VHF radio and radar are all 'line of sight'. Unfortunately there was a 12,500" mountain between them (which none of the crew twigged to).