WABC IBOC Aircheck

[vsa]

Lino,

Are you familiar at all with Leonard Kahn's CAM-D system?

http://www.wrathofkahn.org/

 

[in3media_be1]

Some of the posts in this thread have been moved to TAKE IT OUTSIDE


http://www.radio-info.com/smf/index.php/topic,78731.msg575735.html#msg575735

 

[LinoNYC]

Are you familiar at all with Leonard Kahn's CAM-D system?

Yes, to an extent. The whole iboc vs. cam-d vs. everything else is so polarized and all camps keep alot of what's under the hood secret, it's hard to get accurate info.

A few years ago I heard what purported to be a cam-d a test aircheck, ( i may still have it) It was more of the same grafted on half-assed digital hacks. As I understand the process, cam-d uses analog for bass and mid frequencies and a low-bitrate stream for "highs'.

Obviously this means that the system is vulnerable to interference unless some sort of receiver-based noise blanking is incorporated. It also has no provision for an all-digital option..


If iboc fails the next step should be to widen the mask back to 15K mandate strength-based wideband switching (alread exists) and incorporate receiver based buffering-noise reduction.

Linked in another thread is this articlehttp://www.rwonline.com/pages/s.0049/t.7843.html

Quoting: In particular, Gray does not understand why after establishing the NRSC AM preemphasis/deemphasis and broadcast audio transmission bandwidth specifications to reduce interference on analog AM in the late 1980s, the industry would seemingly go along with a digital system that he said creates data noise.

Two points; when I first heard of an actual proposal for AM digital in 1989, no one had any real concept of how it would be done there wasn't anything such as compressed digitization -atleast no working model. Ofcourse any digital recording is sampling and a form of compression.

The other point is my opinion, AM in the late 80s was still living off very desireable demo's, it hadn't hit crunch time yet. In the intervening years it's audience has aged, and it's sound quality has fallen further back in comparative terms.

I don't believe AM, as we know it has another decade of viability if action isn't taken.


Alot of what I have read from engineers surprises me such as “AM IBOC totally blows this foundation away,” Berlen said. “It is astonishing to me that AM stereo was implemented over two decades ago and with minimal impact on adjacents.

“With today’s technology, we should have been able to do better.”

Sort of like saying, this is 2007 why doesn't my dial-up work like DSL.

As i understand it there isn't enough bandwidth to "do better" unless you turn-off the analog carrier. I have seen a spectrographic display of an AM iboc transmission. You can clearly see that real digital only exists up to approx 4.5 khz above that it's all spectral replication.. The first dem's for AM iboc sounded truly awful but went to 20khz after they stopped trying to cram so-much data and reduced it to 15K things improved to what they are today. Again, not enough bandwidth to do everything.

Lino

 

[Chuck]

.... Again, not enough bandwidth to do everything.

Lino

That IS the basic problem.... All things considered, it's a miracle it works at all.

 

[wgliradio]

Which it doesn't

The HD signals in the new JVC cover about 1/4 of the analog coverage. Which means the HD-1's dropping out in Massapequa LI and, on the North Shore, I had dropouts in Brookville LI along the Gold Coast (there are spots just west of Brookville where you can see the Manhattan skyline).

The AM's had almost no coverage in Suffolk County at all and some spotty coverage in Nassau, with the exception of WCBS/WFAN which sits right off of northern Nassau in Long Island sound and is a blowtorch into Nassau.

Upstate, there were issues in Westchester with the HD-1 as I passed thru on the Cross Westchester in White Plains. The AM's were toast by the Tappan Zee.

I may add that many of the HD2's sound awful, especially WPLJ, WQHT and WRKS. WPLJ is missing one channel of audio information and is creaming the codec, the HD-3 sounds much better.

WQHT sounds like they are using a $5.00 compressor/limiter and WRKS sounds like the audio is out of phase.

Otherwise, it's fine.