FM Translators - Source & Fidelity

[kfbkfb]

Here in KC, I listen to 1 FM translator - 106.9 which is KPRS FM HD2.

IIRC, (FM) HD has a maximum of 8 separate audio programs (with a fidelity reduction due to a low maximum data rate for each of the 8 simultaneous programs).

Does the FM translator have to be fed the actual HD data reduced audio or can it (is it) fed from the high(er) fidelity audio prior to the HD audio codec?


Kirk Bayne

 

[PTBoardOp93]

In many cases, including 106.9 K295CH in Kansas City, a translator can be fed directly from the studio, such as by a microwave link.

 

[Kelly A]

Anymore, likely an Internet connection.

 

[Ryan Williams]

Here in KC, I listen to 1 FM translator - 106.9 which is KPRS FM HD2.

IIRC, (FM) HD has a maximum of 8 separate audio programs (with a fidelity reduction due to a low maximum data rate for each of the 8 simultaneous programs).

Does the FM translator have to be fed the actual HD data reduced audio or can it (is it) fed from the high(er) fidelity audio prior to the HD audio codec?


Kirk Bayne

Any serious translator, especially the commercial ones, will be fed directly via point to point link or in some cases internet. Preferably with redundant providers.

 

[kfbkfb]

My main question - is the audio for the FM translator taken from before the HD data reduction audio codec processing (thereby not subject to the anomalies of stereo audio data reduction) or after (the FM translator signal would then contain the HD data reduction anomalies)?

One of my interests is using, for example, 106.9 as a stereo sound source for creating fake surround sound with my Quadraphonic Hi-Fi (and Dolby Pro-Logic 2 music mode).


Kirk Bayne

 

[PTBoardOp93]

My main question - is the audio for the FM translator taken from before the HD data reduction audio codec

Yes.

 

[fybush]

Kirk, the "data reduction audio codec processing" takes place nearly at the end of the transmission chain, in what's called the "exporter," which takes all the audio and data sources that will become part of the HD Radio bitstream and combines and encodes them to create that bitstream.

In almost all cases, a translator carrying the same programming that's on the HD subchannel will have split off its audio feed somewhere before the exporter. Usually you'll take an extra output from the audio processor and feed that to the IP codec or microwave STL that goes to the translator's transmitter site.

The quality of that IP codec can vary greatly, of course. It could be a mediocre Barix box or a better unit from Comrex or Tieline or GatesAir. And the quality of the audio processing can also vary greatly. It can be anything from a top-of-the-line processor like an Omnia 11 or Optimod 5950 down to the built-in processing in a BW transmitter.

If you're looking for audiophile quality, you probably won't find it here, or anywhere on the FM dial. Everything is pretty loud and crunched these days no matter how it's fed.