[BC] Re: TV Network Audio

[Don Worsham]

> [Hultsman quoting Adams:]
> 
> >>...do any of you buckeroo's or buckerette's  remember when the networks 
> >>went from the poor 8kc loops (at best) to  better multiplexed audio even 
> >>before satellites?
> >
> >That was when the regular networks switched to the video imbedded audio as 
> >PBS had done to get the NPR radio network going.   I remember locally when 
> >the Johnny Carson theme was played...
> 
> When Carson was still in NYC, the audio here at almost the far end of the 
> network was awful, even unintelligible at times.
> 
> Early one morn in the late sixties, a space launch was scrubbed 
> unexpectedly, and we were treated to half an hour of undelayed network 
> schedule feed (a "Beverly Hillbillies" rerun). It was quite ghosty and also 
> had nearly-unintelligible audio. Three hours later, the same episode 
> appeared again, sharp and clear as usual.
> 
> I then realized that most of what we saw in the Northwest originated in Los 
> Angeles from separate copies of tape and film shown the same day in the 
> East, shipped one way or the other in advance, similarly to how Hawaii was 
> served.
> 
> But the other same-day, tape-delayed network programs we saw (news, Today 
> Show, etc.) were not so obviously degraded as Carson. They must have been 
> engineered to compensate for the cross-country haul: simple sound, plain, 
> highly-lighted sets, and restricted motion.
> 
> (Trivia Q. What city was the furthest in circuit-miles from NY? Hint: 
> A'ways east of us.) 
> 
> _______________________________________________
> 


Network audio improved when video transmission included 2 FM subcarriers for 
audio were transmitted with video in a process called as Diplexed audio. Sub carriers 
were typically at 5.8 and 6.2 megs, FM modulated with a 75 microsecond pre-
emphasis. This was in the mid to late 1970s.

This ended the separate copper path for audio and improved the audio bandwidth 
from the typical 5 to 8 khz to 15 khz. In as much as 2 channels were proved, this 
simplified the transition to stereo programming that was occurring at the same time.
The audio subcarriers were demodulated at the local stations.

Those familiar with analogue satellite audio will recognized these audio subcarrier 
frequencies. Satellite video circuits also used a  6.8 meg subcarriers as well as 5.8 
and 6.2.

The improvement in audio response did come at the expense of High Frequency 
headroom or the dreaded "sibilant smear". The use of separate HF limiters did not 
come into common practice until the networks, specifically NBC, started direct 
satellite distribution to their affiliates.  


"Don Worsham" media at gte.net