Why do some HD stations seem to improve in quality when HD kicks in, but w/other stations, there's no difference in quality from the Analog FM signal?

[Wolfie770]

(Sorry for the Twin Cities-centric nature of this)
It seems like stations like KTCZ (Cities 97), KQQL (Kool 108), KCMP (89.3 The Current) and KSJN (Classical MPR) seem to become brighter, cleaner & clearer. It's most noticeable on Classical MPR. But with stations like KSTP-FM (KS95), KXXR (93X), KQRS (KQ92), and KDWB? There doesn't really seem to be that "brightness, cleanness & clearness" that the other Stations have when the HD kicks in?
I can understand KSJN & KCMP, they only have HD-2s, but KTCZ and KQQL have HD-2s and HD-3s. KQQL I can see, with news on HD-2 and Sports on HD-3, having a lot of bandwidth to throw at the HD-1, but both KTCZ and KDWB have HD-2s and HD-3s, boths HD subchannels are all music-based - yet KTCZ HD-1 sounds better when the HD kicks in, but KDWB HD-1 doesn't seem to have much of any difference?
Why does KSTP-FM sound the same on HD as FM when it only has a repeat of KSTP-AM on it? Is it processing or is it inherent to how stations set up their HD subchannels and bitrates?

 

[fybush]

It's mostly a matter of processing. There's an art to processing an HD so that you can take advantage of HD's benefits (no 75-microsecond preemphasis, lower noise floor, more dynamic range) while not creating too jarring a contrast when listeners' radios switch back and forth between HD and analog.

Some broadcasters don't do much in the way of separate processing for HD, and those tend to be the ones that end up sounding just like analog FM on their HDs. Newer processors usually have their own separate HD chain and outputs, and when configured properly those tend to sound best on HD.

 

[Wolfie770]

It's mostly a matter of processing. There's an art to processing an HD so that you can take advantage of HD's benefits (no 75-microsecond preemphasis, lower noise floor, more dynamic range) while not creating too jarring a contrast when listeners' radios switch back and forth between HD and analog.

Some broadcasters don't do much in the way of separate processing for HD, and those tend to be the ones that end up sounding just like analog FM on their HDs. Newer processors usually have their own separate HD chain and outputs, and when configured properly those tend to sound best on HD.

Yeah, it's weird because both KTCZ and KDWB are both owned by iHeart, but KTCZ seems to really be processing to take full advantage of the HD Signal they broadcast and "Hot 102.5" on HD-3 also sounds good - like a higher quality Internet Stream and K-LOVE on HD-2 sounds like a choppy 128kbps MP3, listenable, but barely, but it seems like KDWB must just process the signal the same for both sides, FM & HD, and State Fair Radio on HD-3 sounds like a mid-tier Internet Stream and Pride Radio on HD-2 sounds really bit-starved, flat, and compressed, the term "canned music" comes to mind, it's even worse the K-LOVE on 97.1. When HD-2 was "Trancid", it never sounded this "canned", I think the HD-3 is overstretching them bitrate-wise. Does KDWB just have an older processor than KTCZ?

It just seems a bit bizarre to me, as they're owned by the same entity. You'd think two iHeart Stations would standardize operations between themselves.

When listening to a Classical Station esp., the transition from FM to HD is "jarring", but in a more astonishing than discordant way - that hiss and noise during the quiet and spoken parts of the programming? It just completely disappears, it gets brighter sounding and the soundstage of the stereo separation improves quite a lot. MPR Classical is probably the only station I'd say that comes close to the "where AM sounds like FM and FM sounds like a CD" claims of the ads in the late-00s, and MPR Classical has an HD-2 for Classical 24 - I can only imagine if all 96-120kbps were put toward one HD-1 signal with the music that needs the higher bitrate.

Jazz stations also sound noticeably better on HD - you get a lot more high freq. response, like KCCK-FM in east Iowa (Jazz88 is analog-only up here). And again, the hiss and chatter just went away when it locked onto the HD Signal. It seems like it's easier to lock onto an HD-FM Signal than an FM Stereo Signal, so long as you can receive the HD signal. Stations with a Jazz format seem to be a lower power than other Formats, harder to lock on FM Stereo (I used to switch to Mono FM on standard radio), but not HD.