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HD radio vs RDS
- Thread starter nd2023
- Start date
Nick said:
Not quite sure what you mean -- but I should mention that both RDS and the HD signal employ "forward error correction"; in other words, some redundant information is sent to help to receiver to recover the original data in the presence of noise. In over-the-air broadcasting, it's necessary to use FEC because (unlike a duplex system such as Ethernet) the receiver has no way to tell the transmitter to resend missing packets and/or reduce bitrate.
If a station wants to improve its RDS coverage, the 57 kHz subcarrier injection can be increased as high as 20 percent while also operating in stereo, as long as no other SCA subcarriers are being sent. However, in most cases, RDS decodes well with as little as 3 percent injection (2.5 kHz devation), thanks to FEC.
I notice that the RDS display for a weak signal has some characters changed or missing. For example "Bad Rona ce by Lady Gaba on 94M5 PST" or "Bad Ro94.5 PST"
But if HD signals are weak, it just drops completely. It would sound better, at least to me, if the HD radio just decoded everything, even if it's corrupted by noise.
But if HD signals are weak, it just drops completely. It would sound better, at least to me, if the HD radio just decoded everything, even if it's corrupted by noise.
Living somewhere where summer thunderstorms often interrupt satellite TV broadcasts, I'd have to say no the idea of HD decoding error-prone data. What I get on the telly-vision is lots of top-volume clicks and chirps and squeals interrupting the audio stream right before it craps out. It's VERY annoying to listen to.
I'm curious about your issue with RDS text getting garbled. HD Radio has its own text transport as part of the digital stream, that's separate from the analog RDS. I don't think I've ever seen a HD text line get messed up, and I've got a defectively poor radio, so I go through tons of dropouts and problem areas.
Do some radios eschew the HD text for the RDS text or something? Most stations I've sampled have different data for HD than RDS. On HD, they all have static call letters and station name, or song title and artist, whereas on RDS most these days have scrolling data where the station name should be, which introduces a lot of change for garbled displays since that field should really be static. Changing text should be in the R-Text field instead, but many radios don't support that.
I'm curious about your issue with RDS text getting garbled. HD Radio has its own text transport as part of the digital stream, that's separate from the analog RDS. I don't think I've ever seen a HD text line get messed up, and I've got a defectively poor radio, so I go through tons of dropouts and problem areas.
Do some radios eschew the HD text for the RDS text or something? Most stations I've sampled have different data for HD than RDS. On HD, they all have static call letters and station name, or song title and artist, whereas on RDS most these days have scrolling data where the station name should be, which introduces a lot of change for garbled displays since that field should really be static. Changing text should be in the R-Text field instead, but many radios don't support that.
I've never seen HD text garbled. First the call letters show up, then the song title, then the HD decodes as the signal strength increases.
The station I was referring to, 94.5 WPST, doesn't have HD (and at this point, never will). That station scrolls the song title and station name in the same line "Bad Romance by Lady Gaga on 94.5 PST" would scroll when the station's playing that song.
The station I was referring to, 94.5 WPST, doesn't have HD (and at this point, never will). That station scrolls the song title and station name in the same line "Bad Romance by Lady Gaga on 94.5 PST" would scroll when the station's playing that song.
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