Saturday, December 3, 2011

DRM and Analog "live together in perfect harmony"

Here is a screen grab (click the image for zoom) I took during Disco Palace NA hour [2000-2100 UTC] on 17755kHz (Montsinery) with 17675kHz (RCI, Sackville, Portuguese). What you see is DRM 10kHz on the left and analog AM 10kHz on the right.

I know we have read over and over in journal articles where "simulcast mode" hasn't lived up to expectations (and yes, I realize that these 2 stations are nearly 3000 miles apart) but I could easily listen to one or the other with little or no interference to the analog and no interference to the DRM (at nearly 30dB SNR!)

Using HDSDR, Pappradio 2 USB and a newly acquired M-Audio Sonica Theater USB sound card at 96kHz sampling rate, I had gorgeous copy of both. This tells me two things...simulcast CAN work and that digital and analog can "live together in perfect harmony" just like Paul McCartney and Stevie Wonder!

Using HDSDR, I was able to set the bandwidth perfectly (some receivers might have trouble in this area). For me this is proof of concept. Newer hardware needs tighter filters are more adjustability. RNZI is often transmitting in both DRM and analog, but keeps the signals far apart frequency wise. I'd like to see some 20kHz DRM simulcast experiments so we (as real-world monitors) can judge for ourselves. My hunch is that it would work fine in most case.