[BC] I got my HD radio

[Robert Orban]

At 04:17 AM 12/8/2005, you wrote:
>From: Robert Meuser <robertm at broadcast.net>
>Subject: [BC] I got my HD radio
>To: Broadcast <broadcast at radiolists.net>,       Broadcast Radio Technical
>         Forum <radio-tech at broadcast.net>
>Message-ID: <4397B00D.5000700 at broadcast.net>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>I just purchased a Boston Acoustics receptor. Look for more detailed
>reports in other forums. Initial reaction - disappointment. By the time
>I got home with my purchase it was too late to evaluate AM.  For FM WNYC
>(PBS) and most of the Clear Channel stations where 'perfect' if you
>considered blend. The bad part is that means the blend is so subtle that
>there is no real discernible difference. WPLJ (ABC) also fits that
>category and remains the loudess most obnoxious station in the market.
>Their IBOC signal seems to proove that there is a lot of L R clipping
>happening.

If there is ANY L/R clipping appearing in the HD channel processing of a 
station, then someone made a big mistake setting up the facility or the 
processing. In Optimod HD processors, there are no clippers in the HD 
channel so you couldn't purposely add L/R-domain clipping even if you 
wanted to. L/R clipping is just about the worst thing you can do to a low 
bit rate codec because the codec starts wasting bits trying to encode the 
clipping distortion.

The only peak limiting in an Optimod HD processing chain is the look-ahead 
limiter right before the output, and the output waveform of the look-ahead 
limiter looks nothing at all like the output of a clipper. If you see 
clipping at the processor's output, this would have to be caused by 
clipping in the source mastering process, insufficient headroom in the 
program chain somewhere before the on-air processing, and/or overdriving 
the processor's A/D converter if the unprocessed signal is analog, which is 
rare in major markets these days.

(BTW, I am awaiting delivery of my Boston Acoustics Receptor. I order it 
from Crutchfield and expect it by the end of the week.)

Bob Orban