http://radioink.com/HeadlineEntry.asp?hid=137302&pt=todaysnews

It's going to be a couple months before it takes effect.

They also approved the extended hybrid mode for FM HD, which increases the HD data rate.

it will be interesting to see how this works out my main concern is interference, IBOC can take up to 20 KHz of spectrum to work correctly and also analog signals will cause problems with the digital side bands. I have seen this kind of effect on KEX 1190 as there is an analog station KLAY 1180 that is not only audible but affecting the side bands from KEX negatively at night it might be almost impossible to get the digital signals since the analog signals can be so strong that the digital sidebands are covered. This whole ruling might be a lost cause because of the already over-crowded AM broadcast band but only time will tell.

Doesn't this put FM HD at somewhere around 150Kbps?

If so, we can get a full quality primary stream, and a really solid secondary, with room for the program guide and other goodies right?

...or three streams, but that seems goofy at the moment.

Interesting indeed! I am excited about the possibility of AM HD Dx, but how well will it work, and what favorite Dx stations will be covered by local (and perhaps Dx IBOC sidebands)? I believe that it is necessary to receive only one IBOC sideband to hear the station, so that opens the possibility of Dxing a station when the analog is covered by a local, but either upper or lower IBOC "sidebands" are in the clear!

IS KGO running IBOC yet?

Missing_KSKD: I think the max is about 136 Kbps, without turning off the analog stereo.

Hmmm...

When I wrote my HD Radio paper, that rate was 150 or so. Seems we still are hearing the little details come out. At that time, analog stereo was not a part of the discussion. There was concern about the extended mode causing other problems, but not that one!

Bummer, as that will keep the secondary streams somewhat limited, or both streams limited, or no extra data stuff...

I think KGO is running HD right now but daytime only of course it is possible to do AM HD DX right now but during critical hours only and with FM as well IBOC IDs have been received through tropospheric ducting and E-skip on the FM band no reports of successful audio decoding yet.

Kent, how is 1640 doing with its IBOC plans and do you have any thoughts about why they turned in their nighttime CP? Thanks!

Semoochie: I don't know, but I'll e-mail John White and find out.

FM HD Raio MP1 at 96 kbps is what we all do now, Extended Hybrid mode MP2 is 121 kbps, MP3 full Extended Hybrid Mode is 147 kbps, and full digital Only mode is 277 kbps

There is lots of HD Radio info and a copy of the NPR report on Extend Hybrid Modes and interference at http://www.npr.org/euonline/

Thanks, Kent! I just wondered. the whole thing seemed so out of the blue. Do you think KPOJ will make another attempt?

That clears quite a few things up Kent.

Thanks for the interesting link.

Kind of hoping KPOJ doesn't. My existing radios work just fine! The KEX experience has not been all that good, frankly.

Kent:

Thanks for the Kbps numbers! But where did I go wrong in my estimate? The present (MP1) system uses IBOC carriers from about 129.4 to 198.4 Khz on either side of the FM center frequency to support a 96Kbps digital rate, or about 1.4 Kbps per Khz. The maximum "Extended Hybrid" mode adds Iboc carriers between 101.7 Khz and 128.9 Khz, or an additional 27.2Khz. If the same scale factor can be applied, this would yield another 38 Kbps, or a total of about 134 Kbps. (my estimate above was "about 136") Is there some "overhead" that I failed to account for, or perhaps the "extended hybrid" mode is more efficient somehow?

confused,
jr

Perhaps the overhead of error correction drops with the greater bandwidth?

According to the Ibiquity documentation (if I'm reading it right!), MP1 Mode gives you a P1 98.4 Kbps channel with a "Relative Robustness" of 2.

MP3 Mode adds a P3 24.8 Kbps channel with a "Relative Robustness" of 4, so the extra channel has less error correction.

It took KEX a while to make HD work in their non-directional day mode.

So far, they haven't been able to make KPOJ work, apparently because of how the towers are spaced and interact.

It takes a very-well engineered, or re-engineered, system to do AM HD Radio.

Thanks, Kent!

"relative robustness"

Cut me a break!!

"Relative robustness" is just a measure of how many bits can be missing from the bottom (transmission) layer without it affecting the top layer. Do you know of a better way to measure this? I don't and I'm surprised. Digital data transmission has been around for over forty years, yet I can't think of an accepted standard to measure it with.

Somehow, I fail to understand or realize why the push to have AM HD radio at KEX and KPOJ. They are Clear Channel stations. CC has stated from way up there that talk stations on AM don't need the high frequency response or bandwidth so they wanted to limit the response to less than normal.... I don't remember the actual cutoff point right now.

This is "talk" radio. not Mozart or Beethoven. Not even Pop music. While I prefer to have good frequency response even for voice, I fail to understand why CC would push to have HD on AM when they don't believe they need it normally (standard definition).

Just my thoughts.

Not sure either. But, last time I checked, there were still some Talk stations running AM Stereo.

Actually, that is something I could understand, back in the days when people actually had AM Stereo receivers. The AM Stereo receivers that I saw back then actually did give you a clearer, richer sounding Talk station in Stereo mode. But, today, AM Stereo actually makes for more muddy sounding audio on those modern receivers that don't compensate for AM Stereo. My PT Cruiser car radio does, but a friend's VW New Beetle does not.

I have to say that LimBlah sounds pretty nice in HD... too bad I have no desire to listen to his show.