Until I have a Digital Radio Mondiale Title 47, Part 15.219 transmitter in my hands, I've been experimenting with the digital modes found in FLDigi, primarily MFSK32. Versus SW, the benefit on MW probably isn't as great using MFSK32 over analog. Regardless, I'm finding improved range using MFSK32 on MW, i.e. the digital signal can be properly decoded further from the transmitter than analog. Some preliminary testing indicates the usable decodable range for MFSK32 indoors is a radius of ~ 3 residential city blocks. Preliminary testing indicates the usable decodable range for MFSK32 outdoors is a radius of ~ 5 residential city blocks.
Now, if only the potential audience is willing to tolerate the hassle of using a computer and FLDigi to decode the digital signals ... which is the whole reason for DRM. Like VOA's radiogram on SW, I'm willing to broadcast digital segments on MW using my Part 15.219 transmitter as it adds versatility and increased capability of communicating a message, i.e. text and graphics in addition to audio.
There is a whole unexplored world out there for part 15 digital experimentation.
Ham radio has long been a primary source for radio innovation. It's still alive and thriving. All of what they do can be applied to part 15. There is also the DRM cult phenomenon. A whole bunch of people all over the world are experimenting with DRM receiver technology. It's fun to search YouTube for "DRM radio". You can hear a lot of recieved signals. The quality is hi-fi.
All the digital transmission methods in experimentation seem to start with PC programs that generate the digital modulation at base-band through the PC's audio sound card. A transmitter then up-converts or heterodynes the base-band signal to the desired RF frequency. This is basically the reverse of the process done by variously named "synchrodyne", "zero IF", or "synchronous detetror" receivers.
A transmitter suitable for up-converting the sound card output for part 15 use could be offered by a commercial manufacturer if there is a market large enough to cover design and production costs. One manufacturer has already come and gone. Otherwise, there aren't any currently.
US HD radio would be immediately excluded because the cost of a license from Ibiquity to transmit would be a killer. DRM and other open digital systems don't require a license fee.
This all is something to watch.
Very favorable things are said about the DRM method for digital broadcasting by Keith Perron of PCJ Media, producer of Media Network Plus and who happens to be doing a lot of experimenting with shortwave transmitters.
This is my question right now: can DRM be broadcast along with analog audio on an AM tranmitter, the same way iBuzz currently is by some stations?
If so, I might consider experimenting with it.
The idea of an all digital AM band seems like a rather ugly thing, since it would end the romance of AM DXing, but having analog and digital together seems like fun.
vsb8 (QAM) TV in the 902-928 mhz band is another idea using 1 watt and a 6dbi omni
it could be decoded by common unencrypted digital cable tuners