WABE adds Spanish language stream "Ahora" (HD4?)

[wbz1030]

I noticed that the WABE section on the PBA.org website has been updated. They have updated their program schedule for the HD2 and HD3 streams. They have also added and are promoting the Spanish language stream "Ahora" on the PBA website. Ahora is a service provided by NPR and RNW to NPR affiliates. A link at PBA.org is provided for the Ahora internet stream. PBA.org also has the full schedule available for Ahora.

They don't really give details of how to receive the Ahora stream OTA but I am assuming it is a HD4 stream on WABE's HD Radio digital signal. I have a BA Recepter HD radio and it can receive the WABE HD1, HD2, and HD3 streams but no HD4 stream. Is it on air or is it a quirk on my receiver that I can not pick-up an HD4 stream?

 

[BarryATL]

Is there enough bandwidth to do an HD-4 with the analog still on the air?

We need input from our engineering types.

 

[wbz1030]

WABE and most FM stations that are running iBiquity's HD Radio IBOC system should have the bandwidth if they follow the migration path outlined in the following White Paper...

http://www.ibiquity.com/i/pdfs/Waveforms_FM.pdf

Using the mode terminology in the paper linked used by iBiquity, WABE must be operating in an extended hybrid mode beyond the basic hyrbrid mode "MP1" which offers 96 Kbps (129.3-198.4 KHz) of bandwidth. That is in "MP2" offering 108 Kbps of BW (122.4-198.4 KHz) or "MP3" offering 120 Kbps of BW (115.5-198.4 KHz). As you progress in extended hybrid modes, more of the spectrum closer in to the main analog FM signal is being used.

In theory a station can mulitcast up to 7 or 8 channels, so there is sufficient bandwidth to offer an "HD4" channel by WABE. The HD4 channel must be compressed pretty well down to about 12 kbps or so.

 

[ssnake]

I'm not that familiar with the extended service modes, but doesn't that mean that the additional stream would be less reliable? How does it affect WABE's SCAs? Are they reducing total modulation for the analog so as not to interfere?

 

[RadioFlyerAtl]

I don't believe this stream is actually available on one of the HD SPS channels of 90.1. If I'm wrong, please correct me (John?). However, the last time I checked, every station running HD in the Atlanta market was operating in MP1. This is the mode that pretty much everything related to FM HD was designed for and is specified for. When you move into those extended hybrid modes, you also have to increase your transmitter overhead for the increase in average and peak power for those additional carriers.

However, you can customize your setup with extreme flexibility. In fact, you should be able to get three SPS channels in addition to your main channel while still operating in MP1. With the latest Ibiquity software release, you can now take the main channel down to 32 kbps, which leaves you with about 66 kbps to divide up for your SPS and SIS channels. Saying you wanted to run PSD (PAD) for each of those three SPS channels, you could still get approximately 20 kbps on each stream. Again, not completely sure it can be done, but just believing that it can from what I've seen.

Having said all that, while I am a fan of choice and diversity on the airwaves, I'm not a big fan of the audio quality at the lower data rates. HD sounds pretty good when you don't start etching away at the bandwidth. The full 96 kbps is pretty good, while 64 kbps isn't bad. Once you hit 48 kbps and below, the artifacts start to get annoying (to me). But you can't have your cake and eat it too - it's either quantity or quality.