DRM vs. analogue transmissions of All India Radio2
I then recalled that I had encountered this discrepancy in the quality of AIR's transmissions once before and tweeted about it. Below are the tweets comparing the DRM transmission on 7550 kHz to the analogue signal on 11670 kHz back in May 2015.
The reason this surprised me so much was that All India Radio didn't always sound so bad in DRM. Here's a recording I made in October 2013 on a Morphy Richards DRM receiver:
It turns out that the reason for this drastic change is the fact that All India Radio now combine two audio streams in one DRM feed (one stream per language service), as noted by Andrea Borgnino on Twitter:
It's a very cool feature of the DRM standard but unfortunately leaves around 9kbps of bandwidth per stream, resulting in rather terrible audio. The ironic part is that I don't even know how to select the second stream on my DR111 unit and would have to use one of my SDRs together with Dream to take advantage of it. I hope AIR revert to better quality DRM feeds in the future.