短波のデジタル音声放送
https://www.drm.org/drm-in-the-world/broadcast-schedule/
日本で聞こえそうなのは、ニュージーランドから送信されている。Radio New Zealand International
GMT 1650-1900 9.780 / JST 0150
GMT 1900-2100 12.840 / JST 0400
IC-7300の12Khz IF出力をUSB経由でPCで受け取って"DReaM"というソフトでデコード再生できるらしい、
https://www.reddit.com/r/RTLSDR/comments/grp6m2/dream_v221_for_windows_with_xheaac_support/
怪しいDRM放送
北朝鮮から標準でないDRM放送が行われている模様。日本でなら簡単に受信できるはす。
GMT 2000-1800 3.205 / JST 0500-0300
GMT 2000-1800 6.140 /
2024年の途中で標準準拠ではなくなった模様。北朝鮮国内のアナログ再送信局への配信用なので海外の一般的に再生できなくても問題ないという説が有力。
Very late every night here on the west coast of the US, North Korea's two DRM stations roll in on 6140 and 3205 kHz. But they're never decodable to audio even when the signal is strong. The stream ID is nonstandard, ie, it's not the usual AAC codec variant.
Incompetence could explain it, but the longer it continues the more another explanation suggests itself: this could be a modern counterpart to the classic shortwave "numbers" station transmitting to its overseas spies. DRM is orders of magnitude faster and much less training is required to receive it: just a general purpose SDR, computer, and the right software. And it's just as covert as a classic Cold War numbers station: there's no way to know who's receiving it. That's a powerful advantage vs the Internet when you're trying to stay hidden.
Cuba is known to send encrypted digital data on AM broadcast transmitters using special modulation, but why not just use DRM? It's engineered specifically to broadcast bits over HF channels and hardware and software for it already exists.